diff --git a/Directory.Build.props b/Directory.Build.props
index 7be4ffb..b4b6a5f 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -1,7 +1,8 @@
 <Project>
   <PropertyGroup>
     <LangVersion>12.0</LangVersion>
-    <Nullable>enable</Nullable>
+    <Nullable Condition="'$(TargetFramework)' != 'netstandard2.0'">enable</Nullable>
+    <Nullable Condition="'$(TargetFramework)' == 'netstandard2.0'">annotations</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
 
diff --git a/Singulink.Globalization.Currency.sln b/Singulink.Globalization.Currency.sln
index 55b78d9..8d16861 100644
--- a/Singulink.Globalization.Currency.sln
+++ b/Singulink.Globalization.Currency.sln
@@ -41,6 +41,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = ".github", ".github", "{764A
 		.github\dependabot.yml = .github\dependabot.yml
 	EndProjectSection
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Singulink.Globalization.Currency.NetStandardTests", "Tests\Singulink.Globalization.Currency.NetStandardTests\Singulink.Globalization.Currency.NetStandardTests.csproj", "{A95689C0-68A0-4457-9B2C-0357468920AE}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -55,6 +57,10 @@ Global
 		{FE384100-51BA-42C4-B269-F0C3BCF5A6BE}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{FE384100-51BA-42C4-B269-F0C3BCF5A6BE}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{FE384100-51BA-42C4-B269-F0C3BCF5A6BE}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A95689C0-68A0-4457-9B2C-0357468920AE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A95689C0-68A0-4457-9B2C-0357468920AE}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A95689C0-68A0-4457-9B2C-0357468920AE}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A95689C0-68A0-4457-9B2C-0357468920AE}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -64,6 +70,7 @@ Global
 		{FE384100-51BA-42C4-B269-F0C3BCF5A6BE} = {DBA8BA65-D53C-41A8-9534-EAB6AE159CCB}
 		{97D96E55-E2D9-4076-8D71-BA319A703C06} = {DBA8BA65-D53C-41A8-9534-EAB6AE159CCB}
 		{4028E49D-6194-47FA-AEA9-5B046F8013D2} = {2CD9744C-7FC1-485B-BB89-406676D56D25}
+		{A95689C0-68A0-4457-9B2C-0357468920AE} = {2CD9744C-7FC1-485B-BB89-406676D56D25}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {06D2E21A-73BC-4E56-B817-7147C8D79C05}
diff --git a/Source/Singulink.Globalization.Currency/Currency.cs b/Source/Singulink.Globalization.Currency/Currency.cs
index b0b964a..6f95262 100644
--- a/Source/Singulink.Globalization.Currency/Currency.cs
+++ b/Source/Singulink.Globalization.Currency/Currency.cs
@@ -35,7 +35,7 @@ public class Currency : IFormattable
     public Money MinorUnit => new Money(new decimal(1, 0, 0, false, (byte)DecimalDigits), this);
 
     /// <summary>
-    /// Gets a list containing language identifers and currency names.
+    /// Gets a list containing language identifiers and currency names.
     /// </summary>
     public IEnumerable<(string CultureName, string Name)> LocalizedNames => _localizedNameLookup?.Select(kvp => (kvp.Key, kvp.Value)) ?? Array.Empty<(string, string)>();
 
@@ -54,7 +54,7 @@ public class Currency : IFormattable
     /// is not found.
     /// </remarks>
     public Currency(string name, string currencyCode, string symbol, int decimalDigits, params (string CultureName, string Name)[] localizedNames)
-        : this(name, currencyCode, symbol, decimalDigits, localizedNames.Length == 0 ? null : localizedNames.AsEnumerable()) { }
+        : this(name, currencyCode, symbol, decimalDigits, localizedNames.Length is 0 ? null : localizedNames.AsEnumerable()) { }
 
     /// <inheritdoc cref="Currency(string, string, string, int, ValueTuple{string, string}[])"/>
     public Currency(string name, string currencyCode, string symbol, int decimalDigits, IEnumerable<(string CultureName, string Name)>? localizedNames = null)
@@ -63,16 +63,16 @@ public Currency(string name, string currencyCode, string symbol, int decimalDigi
         name = name.Trim();
         symbol = symbol.Trim();
 
-        if (currencyCode.Length == 0)
+        if (currencyCode.Length is 0)
             throw new ArgumentException("Currency code is required.", nameof(currencyCode));
 
         if (currencyCode.Length > 20)
             throw new ArgumentOutOfRangeException(nameof(currencyCode), "Currency code has a maximum length of 20 characters.");
 
-        if (name.Length == 0)
+        if (name.Length is 0)
             throw new ArgumentException("Name is required.", nameof(name));
 
-        if (symbol.Length == 0)
+        if (symbol.Length is 0)
             throw new ArgumentException("Symbol is required.", nameof(symbol));
 
         if (symbol.Length > 20)
@@ -86,14 +86,23 @@ public Currency(string name, string currencyCode, string symbol, int decimalDigi
         Symbol = symbol;
         DecimalDigits = decimalDigits;
 
-        if (localizedNames != null)
+        if (localizedNames is not null)
         {
-            foreach (var (cultureName, localName) in localizedNames)
+            foreach (var localizedName in localizedNames)
             {
+                string cultureName = CoerceCultureName(localizedName.CultureName);
+                string localName = CoerceCurrencyName(localizedName.Name);
+
                 _localizedNameLookup ??= new(StringComparer.OrdinalIgnoreCase);
+#if NETSTANDARD
+                if (_localizedNameLookup.ContainsKey(cultureName))
+                    throw new ArgumentException($"Duplicate culture name '{cultureName}' in localized names.", nameof(localizedNames));
 
-                if (!_localizedNameLookup.TryAdd(CoerceCultureName(cultureName), CoerceCurrencyName(localName)))
+                _localizedNameLookup.Add(cultureName, localName);
+#else
+                if (!_localizedNameLookup.TryAdd(cultureName, localName))
                     throw new ArgumentException($"Duplicate culture name '{cultureName}' in localized names.", nameof(localizedNames));
+#endif
             }
         }
 
@@ -159,7 +168,7 @@ public string ToString(string? format, CultureInfo? culture = null)
 
         string name;
 
-        if (_localizedNameLookup == null)
+        if (_localizedNameLookup is null)
         {
             name = Name;
         }
@@ -167,7 +176,7 @@ public string ToString(string? format, CultureInfo? culture = null)
         {
             var neutralCulture = culture.GetNeutralCulture();
 
-            if (neutralCulture == null || !_localizedNameLookup.TryGetValue(neutralCulture.Name, out name))
+            if (neutralCulture is null || !_localizedNameLookup.TryGetValue(neutralCulture.Name, out name))
                 name = Name;
         }
 
@@ -220,9 +229,13 @@ internal static CurrencyRegistry CreateSystemRegistry()
 
                 if (localizedNameLookup.TryGetValue(localizationCultureName, out string existingLocalizedName) && existingLocalizedName != localizedName)
                 {
-                    // This shouldn't happen, but if the data changes and it does then make this future-proof by adding the localized name to the specific
-                    // culture instead to override the different neutral culture name that was set.
+                    // This shouldn't happen in .NET+, but if the data changes and it does then make this future-proof by adding the localized name to the
+                    // specific culture instead to override the different neutral culture name that was set.
+
+                    // This *does* happen on .NET Framework, so neutral culture name will be whatever specific culture name was first.
+#if !NETSTANDARD
                     Debug.Fail("Neutral localization culture name was already set to a different name.");
+#endif
                     localizedNameLookup.Add(culture.Name, localizedName);
                 }
                 else
diff --git a/Source/Singulink.Globalization.Currency/CurrencyRegistry.cs b/Source/Singulink.Globalization.Currency/CurrencyRegistry.cs
index d033285..b23abfb 100644
--- a/Source/Singulink.Globalization.Currency/CurrencyRegistry.cs
+++ b/Source/Singulink.Globalization.Currency/CurrencyRegistry.cs
@@ -7,7 +7,12 @@ namespace Singulink.Globalization;
 /// <summary>
 /// Represents a collection of currencies.
 /// </summary>
-public sealed class CurrencyRegistry : ISet<Currency>, IReadOnlySet<Currency>
+public sealed class CurrencyRegistry : ISet<Currency>
+#if !NETSTANDARD
+#pragma warning disable SA1001 // Commas should be spaced correctly
+    , IReadOnlySet<Currency>
+#pragma warning restore SA1001
+#endif
 {
     private static CurrencyRegistry? _default;
     private static CurrencyRegistry? _system;
@@ -25,7 +30,7 @@ public CurrencyRegistry(string name, IEnumerable<Currency> currencies)
     {
         _name = name.Trim();
 
-        if (_name.Length == 0)
+        if (_name.Length is 0)
             throw new ArgumentException("Name is required.", nameof(name));
 
         _currencies = [];
@@ -33,8 +38,19 @@ public CurrencyRegistry(string name, IEnumerable<Currency> currencies)
 
         foreach (var currency in currencies)
         {
+#if NETSTANDARD
+            if (_currencies.Add(currency))
+            {
+                if (_currencyLookup.ContainsKey(currency.CurrencyCode))
+                    throw new ArgumentException($"Multiple currencies with currency code '{currency.CurrencyCode}'.", nameof(currencies));
+
+                _currencyLookup.Add(currency.CurrencyCode, currency);
+            }
+#else
             if (_currencies.Add(currency) && !_currencyLookup.TryAdd(currency.CurrencyCode, currency))
                 throw new ArgumentException($"Multiple currencies with currency code '{currency.CurrencyCode}'.", nameof(currencies));
+#endif
+
         }
     }
 
@@ -51,7 +67,7 @@ public static CurrencyRegistry Default
     {
         get => _default ??= System;
         set {
-            if (_default != null)
+            if (_default is not null)
                 throw new InvalidOperationException("Default currency registry cannot be set after it has already been set or accessed.");
 
             _default = value;
diff --git a/Source/Singulink.Globalization.Currency/IImmutableMoneySet.cs b/Source/Singulink.Globalization.Currency/IImmutableMoneySet.cs
index 1db09df..de08225 100644
--- a/Source/Singulink.Globalization.Currency/IImmutableMoneySet.cs
+++ b/Source/Singulink.Globalization.Currency/IImmutableMoneySet.cs
@@ -153,31 +153,4 @@ public interface IImmutableMoneySet : ICollection<Money>, IReadOnlyMoneySet
     /// Removes all zero amounts from this set and returns the resulting set.
     /// </summary>
     public IImmutableMoneySet TrimZeroAmounts();
-
-    #region Explicit Interface Implementations
-
-    /// <summary>
-    /// Gets a value indicating whether the set is read-only. Always returns <see langword="true"/>.
-    /// </summary>
-    bool ICollection<Money>.IsReadOnly => true;
-
-    /// <summary>
-    /// Not supported.
-    /// </summary>
-    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
-    void ICollection<Money>.Add(Money item) => throw new NotSupportedException();
-
-    /// <summary>
-    /// Not supported.
-    /// </summary>
-    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
-    void ICollection<Money>.Clear() => throw new NotSupportedException();
-
-    /// <summary>
-    /// Not supported.
-    /// </summary>
-    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
-    bool ICollection<Money>.Remove(Money item) => throw new NotSupportedException();
-
-    #endregion
 }
\ No newline at end of file
diff --git a/Source/Singulink.Globalization.Currency/ImmutableMoneySet.cs b/Source/Singulink.Globalization.Currency/ImmutableMoneySet.cs
index ac1ae1f..e37d374 100644
--- a/Source/Singulink.Globalization.Currency/ImmutableMoneySet.cs
+++ b/Source/Singulink.Globalization.Currency/ImmutableMoneySet.cs
@@ -57,7 +57,7 @@ public static ImmutableMoneySet Create(CurrencyRegistry registry, Money value)
         var amountLookup = EmptyLookup;
         var currency = value.CurrencyOrDefault;
 
-        if (currency != null)
+        if (currency is not null)
         {
             EnsureCurrencyAllowed(registry, currency, nameof(value));
             amountLookup = amountLookup.Add(currency, value.Amount);
@@ -88,7 +88,7 @@ public static ImmutableMoneySet Create(CurrencyRegistry registry, Money value)
     /// </exception>
     public static ImmutableMoneySet Create(CurrencyRegistry registry, ReadOnlySpan<Money> values)
     {
-        if (values.Length == 0)
+        if (values.Length is 0)
             return Create(registry);
 
         var builder = EmptyLookup.ToBuilder();
@@ -97,14 +97,14 @@ public static ImmutableMoneySet Create(CurrencyRegistry registry, ReadOnlySpan<M
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             EnsureCurrencyAllowed(registry, currency, nameof(values));
 
             if (builder.TryGetValue(currency, out decimal existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 builder[currency] = existingAmount + value.Amount;
@@ -182,7 +182,7 @@ public ImmutableMoneySet Add(Money value)
     {
         var currency = value.CurrencyOrDefault;
 
-        if (currency == null)
+        if (currency is null)
             return this;
 
         EnsureCurrencyAllowed(currency, nameof(value));
@@ -214,7 +214,7 @@ public ImmutableMoneySet AddRange(IEnumerable<Money> values)
     /// <inheritdoc cref="IImmutableMoneySet.Clear"/>
     public ImmutableMoneySet Clear()
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         return new ImmutableMoneySet(_registry, EmptyLookup);
@@ -285,7 +285,7 @@ public ImmutableMoneySet RemoveAll(IEnumerable<Currency> currencies)
             }
         }
 
-        return builder != null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.RemoveAll(Func{Money, bool})"/>
@@ -302,7 +302,7 @@ public ImmutableMoneySet RemoveAll(Func<Money, bool> predicate)
             }
         }
 
-        return builder != null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.RoundToCurrencyDigits()"/>
@@ -311,7 +311,7 @@ public ImmutableMoneySet RemoveAll(Func<Money, bool> predicate)
     /// <inheritdoc cref="IImmutableMoneySet.RoundToCurrencyDigits(MidpointRounding)"/>
     public ImmutableMoneySet RoundToCurrencyDigits(MidpointRounding mode)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableDictionary<Currency, decimal>.Builder builder = null;
@@ -327,7 +327,7 @@ public ImmutableMoneySet RoundToCurrencyDigits(MidpointRounding mode)
             }
         }
 
-        return builder != null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.SetValue(Money)"/>
@@ -335,7 +335,7 @@ public ImmutableMoneySet SetValue(Money value)
     {
         var currency = value.CurrencyOrDefault;
 
-        if (currency == null)
+        if (currency is null)
             return this;
 
         return SetAmount(value.Amount, currency);
@@ -396,7 +396,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
         bool ignoreZeroAmounts;
         int count;
 
-        if (format != null && format.StartsWith('!'))
+        if (format is not null && format.Length > 0 && format[0] is '!')
         {
             format = format[1..];
             ignoreZeroAmounts = true;
@@ -408,7 +408,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
             count = Count;
         }
 
-        if (count == 0)
+        if (count is 0)
             return string.Empty;
 
         var sb = new StringBuilder(count * 8);
@@ -416,7 +416,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
 
         foreach (var value in this)
         {
-            if (ignoreZeroAmounts && value.Amount == 0)
+            if (ignoreZeroAmounts && value.Amount is 0)
                 continue;
 
             if (first)
@@ -446,7 +446,7 @@ int GetNonZeroCount()
     /// <inheritdoc cref="IImmutableMoneySet.TransformValues(Func{Money, decimal})"/>
     public ImmutableMoneySet TransformValues(Func<Money, decimal> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableDictionary<Currency, decimal>.Builder builder = null;
@@ -462,13 +462,13 @@ public ImmutableMoneySet TransformValues(Func<Money, decimal> transform)
             }
         }
 
-        return builder != null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.TransformValues(Func{Money, decimal?})"/>
     public ImmutableMoneySet TransformValues(Func<Money, decimal?> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableDictionary<Currency, decimal>.Builder builder = null;
@@ -489,13 +489,13 @@ public ImmutableMoneySet TransformValues(Func<Money, decimal?> transform)
             }
         }
 
-        return builder != null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.TransformAmounts(Func{decimal, decimal})"/>
     public ImmutableMoneySet TransformAmounts(Func<decimal, decimal> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableDictionary<Currency, decimal>.Builder builder = null;
@@ -511,13 +511,13 @@ public ImmutableMoneySet TransformAmounts(Func<decimal, decimal> transform)
             }
         }
 
-        return builder != null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.TransformAmounts(Func{decimal, decimal?})"/>
     public ImmutableMoneySet TransformAmounts(Func<decimal, decimal?> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableDictionary<Currency, decimal>.Builder builder = null;
@@ -538,7 +538,7 @@ public ImmutableMoneySet TransformAmounts(Func<decimal, decimal?> transform)
             }
         }
 
-        return builder != null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.TrimZeroAmounts"/>
@@ -548,14 +548,14 @@ public ImmutableMoneySet TrimZeroAmounts()
 
         foreach (var kvp in _amountLookup)
         {
-            if (kvp.Value == 0)
+            if (kvp.Value is 0)
             {
                 builder ??= _amountLookup.ToBuilder();
                 builder.Remove(kvp.Key);
             }
         }
 
-        return builder == null ? this : new ImmutableMoneySet(_registry, builder.ToImmutable());
+        return builder is null ? this : new ImmutableMoneySet(_registry, builder.ToImmutable());
     }
 
     /// <inheritdoc cref="IReadOnlyMoneySet.TryGetAmount(Currency, out decimal)"/>
@@ -612,7 +612,7 @@ private ImmutableMoneySet AddInternal(decimal amount, Currency currency)
             amountLookup = _amountLookup.Add(currency, amount);
         }
 
-        return amountLookup == null ? this : new ImmutableMoneySet(_registry, amountLookup);
+        return amountLookup is null ? this : new ImmutableMoneySet(_registry, amountLookup);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -624,7 +624,7 @@ private ImmutableDictionary<Currency, decimal> AddRangeInternal(IEnumerable<Mone
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             if (ensureCurrenciesInRegistry)
@@ -632,7 +632,7 @@ private ImmutableDictionary<Currency, decimal> AddRangeInternal(IEnumerable<Mone
 
             if (builder?.TryGetValue(currency, out decimal existingAmount) ?? _amountLookup.TryGetValue(currency, out existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 builder ??= _amountLookup.ToBuilder();
@@ -645,7 +645,7 @@ private ImmutableDictionary<Currency, decimal> AddRangeInternal(IEnumerable<Mone
             }
         }
 
-        return builder != null ? builder.ToImmutable() : _amountLookup;
+        return builder is not null ? builder.ToImmutable() : _amountLookup;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -657,7 +657,7 @@ private ImmutableDictionary<Currency, decimal> SubtractRangeInternal(IEnumerable
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             if (ensureCurrenciesInRegistry)
@@ -665,7 +665,7 @@ private ImmutableDictionary<Currency, decimal> SubtractRangeInternal(IEnumerable
 
             if (builder?.TryGetValue(currency, out decimal existingAmount) ?? _amountLookup.TryGetValue(currency, out existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 builder ??= _amountLookup.ToBuilder();
@@ -678,7 +678,7 @@ private ImmutableDictionary<Currency, decimal> SubtractRangeInternal(IEnumerable
             }
         }
 
-        return builder != null ? builder.ToImmutable() : _amountLookup;
+        return builder is not null ? builder.ToImmutable() : _amountLookup;
     }
 
     private void EnsureCurrencyAllowed(Currency currency, string paramName) => EnsureCurrencyAllowed(_registry, currency, paramName);
@@ -707,10 +707,15 @@ static void Throw(CurrencyRegistry registry, Currency currency, string paramName
 #endif
 
     /// <inheritdoc/>
-    bool IReadOnlyMoneySet.IsSorted => false;
+    IReadOnlyCollection<Currency> IReadOnlyMoneySet.Currencies => Currencies;
 
     /// <inheritdoc/>
-    IReadOnlyCollection<Currency> IReadOnlyMoneySet.Currencies => Currencies;
+    bool IReadOnlyMoneySet.IsSorted => false;
+
+    /// <summary>
+    /// Gets a value indicating whether the set is read-only. Always returns <see langword="true"/>.
+    /// </summary>
+    bool ICollection<Money>.IsReadOnly => true;
 
     /// <inheritdoc/>
     IImmutableMoneySet IImmutableMoneySet.Add(Money value) => Add(value);
@@ -798,6 +803,28 @@ void ICollection<Money>.CopyTo(Money[] array, int arrayIndex)
 
     #endregion
 
+    #region Not Supported
+
+    /// <summary>
+    /// Not supported.
+    /// </summary>
+    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
+    void ICollection<Money>.Add(Money item) => throw new NotSupportedException();
+
+    /// <summary>
+    /// Not supported.
+    /// </summary>
+    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
+    void ICollection<Money>.Clear() => throw new NotSupportedException();
+
+    /// <summary>
+    /// Not supported.
+    /// </summary>
+    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
+    bool ICollection<Money>.Remove(Money item) => throw new NotSupportedException();
+
+    #endregion
+
     /// <summary>
     /// Enumerates the elements of a <see cref="ImmutableMoneySet"/>.
     /// </summary>
diff --git a/Source/Singulink.Globalization.Currency/ImmutableSortedMoneySet.cs b/Source/Singulink.Globalization.Currency/ImmutableSortedMoneySet.cs
index aedfe92..fb7de4e 100644
--- a/Source/Singulink.Globalization.Currency/ImmutableSortedMoneySet.cs
+++ b/Source/Singulink.Globalization.Currency/ImmutableSortedMoneySet.cs
@@ -57,7 +57,7 @@ public static ImmutableSortedMoneySet Create(CurrencyRegistry registry, Money va
         var amountLookup = EmptyLookup;
         var currency = value.CurrencyOrDefault;
 
-        if (currency != null)
+        if (currency is not null)
         {
             EnsureCurrencyAllowed(registry, currency, nameof(value));
             amountLookup = amountLookup.Add(currency, value.Amount);
@@ -88,7 +88,7 @@ public static ImmutableSortedMoneySet Create(CurrencyRegistry registry, Money va
     /// </exception>
     public static ImmutableSortedMoneySet Create(CurrencyRegistry registry, ReadOnlySpan<Money> values)
     {
-        if (values.Length == 0)
+        if (values.Length is 0)
             return Create(registry);
 
         var builder = EmptyLookup.ToBuilder();
@@ -97,14 +97,14 @@ public static ImmutableSortedMoneySet Create(CurrencyRegistry registry, ReadOnly
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             EnsureCurrencyAllowed(registry, currency, nameof(values));
 
             if (builder.TryGetValue(currency, out decimal existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 builder[currency] = existingAmount + value.Amount;
@@ -182,7 +182,7 @@ public ImmutableSortedMoneySet Add(Money value)
     {
         var currency = value.CurrencyOrDefault;
 
-        if (currency == null)
+        if (currency is null)
             return this;
 
         EnsureCurrencyAllowed(currency, nameof(value));
@@ -214,7 +214,7 @@ public ImmutableSortedMoneySet AddRange(IEnumerable<Money> values)
     /// <inheritdoc cref="IImmutableMoneySet.Clear"/>
     public ImmutableSortedMoneySet Clear()
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         return new ImmutableSortedMoneySet(_registry, EmptyLookup);
@@ -285,7 +285,7 @@ public ImmutableSortedMoneySet RemoveAll(IEnumerable<Currency> currencies)
             }
         }
 
-        return builder != null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.RemoveAll(Func{Money, bool})"/>
@@ -302,7 +302,7 @@ public ImmutableSortedMoneySet RemoveAll(Func<Money, bool> predicate)
             }
         }
 
-        return builder != null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.RoundToCurrencyDigits()"/>
@@ -311,7 +311,7 @@ public ImmutableSortedMoneySet RemoveAll(Func<Money, bool> predicate)
     /// <inheritdoc cref="IImmutableMoneySet.RoundToCurrencyDigits(MidpointRounding)"/>
     public ImmutableSortedMoneySet RoundToCurrencyDigits(MidpointRounding mode)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableSortedDictionary<Currency, decimal>.Builder builder = null;
@@ -327,7 +327,7 @@ public ImmutableSortedMoneySet RoundToCurrencyDigits(MidpointRounding mode)
             }
         }
 
-        return builder != null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.SetValue(Money)"/>
@@ -335,7 +335,7 @@ public ImmutableSortedMoneySet SetValue(Money value)
     {
         var currency = value.CurrencyOrDefault;
 
-        if (currency == null)
+        if (currency is null)
             return this;
 
         return SetAmount(value.Amount, currency);
@@ -396,7 +396,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
         bool ignoreZeroAmounts;
         int count;
 
-        if (format != null && format.StartsWith('!'))
+        if (format is not null && format.Length > 0 && format[0] is '!')
         {
             format = format[1..];
             ignoreZeroAmounts = true;
@@ -408,7 +408,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
             count = Count;
         }
 
-        if (count == 0)
+        if (count is 0)
             return string.Empty;
 
         var sb = new StringBuilder(count * 8);
@@ -416,7 +416,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
 
         foreach (var value in this)
         {
-            if (ignoreZeroAmounts && value.Amount == 0)
+            if (ignoreZeroAmounts && value.Amount is 0)
                 continue;
 
             if (first)
@@ -446,7 +446,7 @@ int GetNonZeroCount()
     /// <inheritdoc cref="IImmutableMoneySet.TransformValues(Func{Money, decimal})"/>
     public ImmutableSortedMoneySet TransformValues(Func<Money, decimal> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableSortedDictionary<Currency, decimal>.Builder builder = null;
@@ -462,13 +462,13 @@ public ImmutableSortedMoneySet TransformValues(Func<Money, decimal> transform)
             }
         }
 
-        return builder != null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.TransformValues(Func{Money, decimal?})"/>
     public ImmutableSortedMoneySet TransformValues(Func<Money, decimal?> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableSortedDictionary<Currency, decimal>.Builder builder = null;
@@ -489,13 +489,13 @@ public ImmutableSortedMoneySet TransformValues(Func<Money, decimal?> transform)
             }
         }
 
-        return builder != null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.TransformAmounts(Func{decimal, decimal})"/>
     public ImmutableSortedMoneySet TransformAmounts(Func<decimal, decimal> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableSortedDictionary<Currency, decimal>.Builder builder = null;
@@ -511,13 +511,13 @@ public ImmutableSortedMoneySet TransformAmounts(Func<decimal, decimal> transform
             }
         }
 
-        return builder != null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.TransformAmounts(Func{decimal, decimal?})"/>
     public ImmutableSortedMoneySet TransformAmounts(Func<decimal, decimal?> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return this;
 
         ImmutableSortedDictionary<Currency, decimal>.Builder builder = null;
@@ -538,7 +538,7 @@ public ImmutableSortedMoneySet TransformAmounts(Func<decimal, decimal?> transfor
             }
         }
 
-        return builder != null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
+        return builder is not null ? new ImmutableSortedMoneySet(_registry, builder.ToImmutable()) : this;
     }
 
     /// <inheritdoc cref="IImmutableMoneySet.TrimZeroAmounts"/>
@@ -548,14 +548,14 @@ public ImmutableSortedMoneySet TrimZeroAmounts()
 
         foreach (var kvp in _amountLookup)
         {
-            if (kvp.Value == 0)
+            if (kvp.Value is 0)
             {
                 builder ??= _amountLookup.ToBuilder();
                 builder.Remove(kvp.Key);
             }
         }
 
-        return builder == null ? this : new ImmutableSortedMoneySet(_registry, builder.ToImmutable());
+        return builder is null ? this : new ImmutableSortedMoneySet(_registry, builder.ToImmutable());
     }
 
     /// <inheritdoc cref="IReadOnlyMoneySet.TryGetAmount(Currency, out decimal)"/>
@@ -612,7 +612,7 @@ private ImmutableSortedMoneySet AddInternal(decimal amount, Currency currency)
             amountLookup = _amountLookup.Add(currency, amount);
         }
 
-        return amountLookup == null ? this : new ImmutableSortedMoneySet(_registry, amountLookup);
+        return amountLookup is null ? this : new ImmutableSortedMoneySet(_registry, amountLookup);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -624,7 +624,7 @@ private ImmutableSortedDictionary<Currency, decimal> AddRangeInternal(IEnumerabl
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             if (ensureCurrenciesInRegistry)
@@ -632,7 +632,7 @@ private ImmutableSortedDictionary<Currency, decimal> AddRangeInternal(IEnumerabl
 
             if (builder?.TryGetValue(currency, out decimal existingAmount) ?? _amountLookup.TryGetValue(currency, out existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 builder ??= _amountLookup.ToBuilder();
@@ -645,7 +645,7 @@ private ImmutableSortedDictionary<Currency, decimal> AddRangeInternal(IEnumerabl
             }
         }
 
-        return builder != null ? builder.ToImmutable() : _amountLookup;
+        return builder is not null ? builder.ToImmutable() : _amountLookup;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -657,7 +657,7 @@ private ImmutableSortedDictionary<Currency, decimal> SubtractRangeInternal(IEnum
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             if (ensureCurrenciesInRegistry)
@@ -665,7 +665,7 @@ private ImmutableSortedDictionary<Currency, decimal> SubtractRangeInternal(IEnum
 
             if (builder?.TryGetValue(currency, out decimal existingAmount) ?? _amountLookup.TryGetValue(currency, out existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 builder ??= _amountLookup.ToBuilder();
@@ -678,7 +678,7 @@ private ImmutableSortedDictionary<Currency, decimal> SubtractRangeInternal(IEnum
             }
         }
 
-        return builder != null ? builder.ToImmutable() : _amountLookup;
+        return builder is not null ? builder.ToImmutable() : _amountLookup;
     }
 
     private void EnsureCurrencyAllowed(Currency currency, string paramName) => EnsureCurrencyAllowed(_registry, currency, paramName);
@@ -707,10 +707,15 @@ static void Throw(CurrencyRegistry registry, Currency currency, string paramName
 #endif
 
     /// <inheritdoc/>
-    bool IReadOnlyMoneySet.IsSorted => true;
+    IReadOnlyCollection<Currency> IReadOnlyMoneySet.Currencies => Currencies;
 
     /// <inheritdoc/>
-    IReadOnlyCollection<Currency> IReadOnlyMoneySet.Currencies => Currencies;
+    bool IReadOnlyMoneySet.IsSorted => true;
+
+    /// <summary>
+    /// Gets a value indicating whether the set is read-only. Always returns <see langword="true"/>.
+    /// </summary>
+    bool ICollection<Money>.IsReadOnly => true;
 
     /// <inheritdoc/>
     IImmutableMoneySet IImmutableMoneySet.Add(Money value) => Add(value);
@@ -798,6 +803,28 @@ void ICollection<Money>.CopyTo(Money[] array, int arrayIndex)
 
     #endregion
 
+    #region Not Supported
+
+    /// <summary>
+    /// Not supported.
+    /// </summary>
+    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
+    void ICollection<Money>.Add(Money item) => throw new NotSupportedException();
+
+    /// <summary>
+    /// Not supported.
+    /// </summary>
+    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
+    void ICollection<Money>.Clear() => throw new NotSupportedException();
+
+    /// <summary>
+    /// Not supported.
+    /// </summary>
+    /// <exception cref="NotSupportedException">This operation is not supported.</exception>
+    bool ICollection<Money>.Remove(Money item) => throw new NotSupportedException();
+
+    #endregion
+
     /// <summary>
     /// Enumerates the elements of a <see cref="ImmutableSortedMoneySet"/>.
     /// </summary>
diff --git a/Source/Singulink.Globalization.Currency/Money.ToString.cs b/Source/Singulink.Globalization.Currency/Money.ToString.cs
index 5fa5678..197988f 100644
--- a/Source/Singulink.Globalization.Currency/Money.ToString.cs
+++ b/Source/Singulink.Globalization.Currency/Money.ToString.cs
@@ -20,8 +20,10 @@ private static readonly ImmutableArray<string> NegativeInternationalPatterns
     private static readonly ImmutableArray<string> NegativeReverseInternationalPatterns
         = ["(n) $", "-n $", "-n $", "n- $", "(n) $", "-n $", "n- $", "n- $", "-n $", "-n $", "n- $", "n- $", "-n $", "n- $", "(n) $", "(n) $"];
 
-    private static readonly ConditionalWeakTable<CultureInfo, RegionInfo?> _regionInfoLookup = [];
-    private static readonly ConditionalWeakTable<NumberFormatInfo, NumberFormatInfo> _absNumberFormatInfoLookup = [];
+#pragma warning disable IDE0028 // Simplify collection initialization (not supported on NS2)
+    private static readonly ConditionalWeakTable<CultureInfo, RegionInfo?> _regionInfoLookup = new();
+    private static readonly ConditionalWeakTable<NumberFormatInfo, NumberFormatInfo> _absNumberFormatInfoLookup = new();
+#pragma warning restore IDE0028
 
     /// <summary>
     /// Returns a culture-dependent international string representation of this value's currency and amount.
@@ -68,24 +70,34 @@ private static readonly ImmutableArray<string> NegativeReverseInternationalPatte
     /// <exception cref="FormatException">Format specifier was invalid.</exception>
     public string ToString(string? format, IFormatProvider? formatProvider = null)
     {
+#if NETSTANDARD
+        ParseFormat(format, out char symbolFormat, out char decimalsFormat, out int decimalsFormatNumber, out char resultNumberFormatType);
+#else
         Span<char> resultNumberFormat = stackalloc char[3];
         ParseFormat(format, out char symbolFormat, out char decimalsFormat, out int decimalsFormatNumber, out resultNumberFormat[0]);
+#endif
 
         CultureInfo culture = GetCultureAndSetFormatProvider(ref formatProvider);
         RegionInfo? region = null;
 
         decimal absFormatAmount = GetFormatAmountAndDecimalPlaces(Math.Abs(_amount), _currency, decimalsFormat, decimalsFormatNumber, out int formatDecimalPlaces);
+        var absNumberFormatInfo = GetAbsNumberFormatInfo(formatProvider);
+
+#if NETSTANDARD
+        string resultNumberFormat = $"{resultNumberFormatType}{formatDecimalPlaces}";
+        string number = absFormatAmount.ToString(resultNumberFormat, absNumberFormatInfo);
+#else
         formatDecimalPlaces.TryFormat(resultNumberFormat[1..], out int formatDecimalPlacesLength, null, CultureInfo.InvariantCulture);
         resultNumberFormat = resultNumberFormat[..(1 + formatDecimalPlacesLength)];
 
         // Enough capacity for whole number (29) + group separators (14) + decimal separator (1) + decimals (29)
         Span<char> number = stackalloc char[73];
-        var absNumberFormatInfo = GetAbsNumberFormatInfo(formatProvider);
 
         if (!absFormatAmount.TryFormat(number, out int numberLength, resultNumberFormat, absNumberFormatInfo))
             throw new UnreachableException($"Unexpected number formatting failure (resultNumberFormat: '{resultNumberFormat}').");
 
         number = number[..numberLength];
+#endif
 
         if (_currency is null)
             return number.ToString(); // number must be zero with no currency so we can stop formatting here
@@ -141,7 +153,11 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
         if (currencySymbol == absNumberFormatInfo.CurrencyDecimalSeparator)
             currencySymbol = string.Empty;
 
+#if NETSTANDARD
+        return ApplyPattern(number.AsSpan(), pattern, currencySymbol, absNumberFormatInfo.NegativeSign, placeCurrencySymbolAsDecimalSeparator);
+#else
         return ApplyPattern(number, pattern, currencySymbol, absNumberFormatInfo.NegativeSign, placeCurrencySymbolAsDecimalSeparator);
+#endif
     }
 
     private static string ApplyPattern(ReadOnlySpan<char> number, string pattern, string currencySymbol, string negativeSign, bool placeCurrencySymbolAsDecimalSeparator)
@@ -162,12 +178,12 @@ private static string ApplyPattern(ReadOnlySpan<char> number, string pattern, st
                         if (decimalIndex == -1)
                         {
                             Append(ref remaining, number);
-                            Append(ref remaining, currencySymbol);
+                            Append(ref remaining, currencySymbol.AsSpan());
                         }
                         else
                         {
                             Append(ref remaining, number[..decimalIndex]);
-                            Append(ref remaining, currencySymbol);
+                            Append(ref remaining, currencySymbol.AsSpan());
                             Append(ref remaining, number[(decimalIndex + 1)..]);
                         }
                     }
@@ -180,11 +196,11 @@ private static string ApplyPattern(ReadOnlySpan<char> number, string pattern, st
 
                 case '$':
                     if (!placeCurrencySymbolAsDecimalSeparator && currencySymbol != Constants.ZeroWidthSpace)
-                        Append(ref remaining, currencySymbol);
+                        Append(ref remaining, currencySymbol.AsSpan());
                     break;
 
                 case '-':
-                    Append(ref remaining, negativeSign);
+                    Append(ref remaining, negativeSign.AsSpan());
                     break;
 
                 case ' ':
@@ -217,7 +233,7 @@ private static CultureInfo GetCultureAndSetFormatProvider(ref IFormatProvider? f
     {
         CultureInfo culture;
 
-        if (formatProvider == null)
+        if (formatProvider is null)
             formatProvider = culture = CultureInfo.CurrentCulture;
         else
             culture = formatProvider as CultureInfo ?? CultureInfo.CurrentCulture;
@@ -242,7 +258,7 @@ private static decimal GetFormatAmountAndDecimalPlaces(decimal amount, Currency?
         if (decimalsFormat == default || decimalsFormat == '*')
         {
             int amountDecimalDigits = amount.GetDecimalDigits();
-            formatDecimalPlaces = decimalsFormat == '*' && amountDecimalDigits == 0 ? 0 : Math.Max(amountDecimalDigits, currency?.DecimalDigits ?? 0);
+            formatDecimalPlaces = decimalsFormat == '*' && amountDecimalDigits is 0 ? 0 : Math.Max(amountDecimalDigits, currency?.DecimalDigits ?? 0);
         }
         else
         {
@@ -265,10 +281,14 @@ private static RegionInfo GetRegionForCulture(CultureInfo culture)
             try
             {
                 region = new RegionInfo(culture.Name);
+#if NETSTANDARD
+                _regionInfoLookup.Add(culture, region);
+#endif
             }
             catch { }
-
+#if !NETSTANDARD
             _regionInfoLookup.AddOrUpdate(culture, region);
+#endif
         }
 
         return region ?? RegionInfo.CurrentRegion;
@@ -332,7 +352,11 @@ void Next()
                     var decimalsFormatNumberSpan = format.AsSpan()[currentIndex..];
 
                     if (decimalsFormatNumberSpan.Length > 2 ||
+#if NETSTANDARD
+                        !int.TryParse(decimalsFormatNumberSpan.ToString(), NumberStyles.None, CultureInfo.InvariantCulture, out decimalsFormatNumber) ||
+#else
                         !int.TryParse(decimalsFormatNumberSpan, NumberStyles.None, CultureInfo.InvariantCulture, out decimalsFormatNumber) ||
+#endif
                         decimalsFormatNumber is < 0 or > 28)
                     {
                         Throw();
diff --git a/Source/Singulink.Globalization.Currency/Money.cs b/Source/Singulink.Globalization.Currency/Money.cs
index 88ac80c..97a83ca 100644
--- a/Source/Singulink.Globalization.Currency/Money.cs
+++ b/Source/Singulink.Globalization.Currency/Money.cs
@@ -45,7 +45,7 @@ public Money(decimal amount, Currency currency)
     /// Creates a new <see cref="Money"/> value with the specified amount and currency code. Allows creating default money values by passing <c>0</c> for
     /// the amount and <see langword="null"/> for the currency code. Currency code must be provided if the amount is non-zero.
     /// </summary>
-    public static Money CreateDefaultable(decimal amount, string? currencyCode) => CreateDefaultable(amount, currencyCode == null ? null : Currency.Get(currencyCode));
+    public static Money CreateDefaultable(decimal amount, string? currencyCode) => CreateDefaultable(amount, currencyCode is null ? null : Currency.Get(currencyCode));
 
     /// <summary>
     /// Creates a new <see cref="Money"/> value with the specified amount and currency. Allows creating default money values by passing <c>0</c> for
@@ -53,7 +53,7 @@ public Money(decimal amount, Currency currency)
     /// </summary>
     public static Money CreateDefaultable(decimal amount, Currency? currency)
     {
-        if (currency == null)
+        if (currency is null)
         {
             if (amount != 0)
                 ThrowCurrencyRequiredForNonZeroAmount();
@@ -99,7 +99,7 @@ public Currency Currency
     /// </summary>
     [MemberNotNullWhen(false, nameof(CurrencyOrDefault))]
     [MemberNotNullWhen(false, nameof(_currency))]
-    public bool IsDefault => _currency == null;
+    public bool IsDefault => _currency is null;
 
     #region Operators
 
@@ -194,13 +194,13 @@ public Currency Currency
     /// </summary>
     public Money RoundToCurrencyDigits(MidpointRounding mode)
     {
-        return _currency == null ? this : new Money(Math.Round(_amount, _currency.DecimalDigits, mode), Currency);
+        return _currency is null ? this : new Money(Math.Round(_amount, _currency.DecimalDigits, mode), Currency);
     }
 
     /// <summary>
     /// Returns <see cref="Default"/> if this value's <see cref="Amount"/> is <c>0</c>, otherwise returns this value.
     /// </summary>
-    public Money ToDefaultIfZero() => _amount == 0 ? default : this;
+    public Money ToDefaultIfZero() => _amount is 0 ? default : this;
 
     #region Equality and Comparison
 
diff --git a/Source/Singulink.Globalization.Currency/MoneySet.cs b/Source/Singulink.Globalization.Currency/MoneySet.cs
index d2fec59..aabf57d 100644
--- a/Source/Singulink.Globalization.Currency/MoneySet.cs
+++ b/Source/Singulink.Globalization.Currency/MoneySet.cs
@@ -72,14 +72,14 @@ public MoneySet(CurrencyRegistry registry, ReadOnlySpan<Money> values)
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             EnsureCurrencyAllowed(currency, nameof(values));
 
             if (_amountLookup.TryGetValue(currency, out decimal existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 _amountLookup[currency] = existingAmount + value.Amount;
@@ -135,7 +135,7 @@ public void Add(Money value)
     {
         var currency = value.CurrencyOrDefault;
 
-        if (currency == null)
+        if (currency is null)
             return;
 
         EnsureCurrencyAllowed(currency, nameof(value));
@@ -232,7 +232,7 @@ public int RemoveAll(IEnumerable<Currency> currencies)
                 count++;
         }
 
-        if (disallowedCurrencies != null)
+        if (disallowedCurrencies is not null)
             ThrowCurrenciesDisallowed(disallowedCurrencies, nameof(currencies));
 
         return count;
@@ -252,7 +252,7 @@ public int RemoveAll(Func<Money, bool> predicate)
             }
         }
 
-        if (currenciesToRemove != null)
+        if (currenciesToRemove is not null)
         {
             foreach (var currency in currenciesToRemove)
             {
@@ -271,7 +271,7 @@ public int RemoveAll(Func<Money, bool> predicate)
     /// <inheritdoc cref="IMoneySet.RoundToCurrencyDigits(MidpointRounding)"/>
     public void RoundToCurrencyDigits(MidpointRounding mode)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         List<KeyValuePair<Currency, decimal>> updatedEntries = null;
@@ -287,7 +287,7 @@ public void RoundToCurrencyDigits(MidpointRounding mode)
             }
         }
 
-        if (updatedEntries == null)
+        if (updatedEntries is null)
             return;
 
         foreach (var entry in updatedEntries)
@@ -301,7 +301,7 @@ public void SetValue(Money value)
     {
         var currency = value.CurrencyOrDefault;
 
-        if (currency == null)
+        if (currency is null)
             return;
 
         SetAmount(value.Amount, currency);
@@ -358,7 +358,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
         bool ignoreZeroAmounts;
         int count;
 
-        if (format != null && format.StartsWith('!'))
+        if (format is not null && format.Length > 0 && format[0] is '!')
         {
             format = format[1..];
             ignoreZeroAmounts = true;
@@ -370,7 +370,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
             count = Count;
         }
 
-        if (count == 0)
+        if (count is 0)
             return string.Empty;
 
         var sb = new StringBuilder(count * 8);
@@ -378,7 +378,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
 
         foreach (var value in this)
         {
-            if (ignoreZeroAmounts && value.Amount == 0)
+            if (ignoreZeroAmounts && value.Amount is 0)
                 continue;
 
             if (first)
@@ -408,7 +408,7 @@ int GetNonZeroCount()
     /// <inheritdoc cref="IMoneySet.TransformValues(Func{Money, decimal})"/>
     public void TransformValues(Func<Money, decimal> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         // TODO: Optimize if no values change.
@@ -427,7 +427,7 @@ public void TransformValues(Func<Money, decimal> transform)
     /// <inheritdoc cref="IMoneySet.TransformValues(Func{Money, decimal?})"/>
     public void TransformValues(Func<Money, decimal?> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         // TODO: Optimize if no values change.
@@ -450,7 +450,7 @@ public void TransformValues(Func<Money, decimal?> transform)
     /// <inheritdoc cref="IMoneySet.TransformAmounts(Func{decimal, decimal})"/>
     public void TransformAmounts(Func<decimal, decimal> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         // TODO: Optimize if no values change.
@@ -470,7 +470,7 @@ public void TransformAmounts(Func<decimal, decimal> transform)
     /// <inheritdoc cref="IMoneySet.TransformAmounts(Func{decimal, decimal?})"/>
     public void TransformAmounts(Func<decimal, decimal?> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         // TODO: Optimize if no values change.
@@ -497,14 +497,14 @@ public int TrimZeroAmounts()
 
         foreach (var kvp in _amountLookup)
         {
-            if (kvp.Value == 0)
+            if (kvp.Value is 0)
             {
                 currenciesToRemove ??= [];
                 currenciesToRemove.Add(kvp.Key);
             }
         }
 
-        if (currenciesToRemove != null)
+        if (currenciesToRemove is not null)
         {
             foreach (var currency in currenciesToRemove)
             {
@@ -573,7 +573,7 @@ private void AddRangeInternal(IEnumerable<Money> values, bool ensureCurrenciesIn
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             if (ensureCurrenciesInRegistry && !_registry.Contains(currency))
@@ -585,7 +585,7 @@ private void AddRangeInternal(IEnumerable<Money> values, bool ensureCurrenciesIn
 
             if (_amountLookup.TryGetValue(currency, out decimal existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 _amountLookup[currency] = existingAmount + value.Amount;
@@ -596,7 +596,7 @@ private void AddRangeInternal(IEnumerable<Money> values, bool ensureCurrenciesIn
             }
         }
 
-        if (disallowedCurrencies != null)
+        if (disallowedCurrencies is not null)
             ThrowCurrenciesDisallowed(disallowedCurrencies, nameof(values));
     }
 
@@ -608,7 +608,7 @@ private void SubtractRangeInternal(IEnumerable<Money> values, bool ensureCurrenc
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             if (ensureCurrenciesInRegistry && !_registry.Contains(currency))
@@ -620,7 +620,7 @@ private void SubtractRangeInternal(IEnumerable<Money> values, bool ensureCurrenc
 
             if (_amountLookup.TryGetValue(currency, out decimal existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 _amountLookup[currency] = existingAmount - value.Amount;
@@ -631,7 +631,7 @@ private void SubtractRangeInternal(IEnumerable<Money> values, bool ensureCurrenc
             }
         }
 
-        if (disallowedCurrencies != null)
+        if (disallowedCurrencies is not null)
             ThrowCurrenciesDisallowed(disallowedCurrencies, nameof(values));
     }
 
diff --git a/Source/Singulink.Globalization.Currency/Singulink.Globalization.Currency.csproj b/Source/Singulink.Globalization.Currency/Singulink.Globalization.Currency.csproj
index 2713b56..6288463 100644
--- a/Source/Singulink.Globalization.Currency/Singulink.Globalization.Currency.csproj
+++ b/Source/Singulink.Globalization.Currency/Singulink.Globalization.Currency.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
-        <TargetFrameworks>net6.0;net7.0</TargetFrameworks>
+        <TargetFrameworks>netstandard2.0;net6.0;net7.0</TargetFrameworks>
         <RootNamespace>Singulink.Globalization</RootNamespace>
 
         <SignAssembly>true</SignAssembly>
@@ -12,11 +12,13 @@
         <PackageProjectUrl>https://github.com/Singulink/Singulink.Globalization.Currency</PackageProjectUrl>
     </PropertyGroup>
 
+    <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+        <PackageReference Include="System.Memory" Version="4.5.5" />
+        <PackageReference Include="Microsoft.Bcl.HashCode" Version="1.1.1" />
+    </ItemGroup>
+
     <ItemGroup>
-        <PackageReference Include="PolySharp" Version="1.14.1">
-            <PrivateAssets>all</PrivateAssets>
-            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-        </PackageReference>
+        <PackageReference Include="PolySharp" Version="1.14.1" PrivateAssets="All" />
         <PackageReference Include="System.Collections.Immutable" Version="8.0.0" />
     </ItemGroup>
 </Project>
diff --git a/Source/Singulink.Globalization.Currency/SortedMoneySet.cs b/Source/Singulink.Globalization.Currency/SortedMoneySet.cs
index 8bbac45..816bada 100644
--- a/Source/Singulink.Globalization.Currency/SortedMoneySet.cs
+++ b/Source/Singulink.Globalization.Currency/SortedMoneySet.cs
@@ -72,14 +72,14 @@ public SortedMoneySet(CurrencyRegistry registry, ReadOnlySpan<Money> values)
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             EnsureCurrencyAllowed(currency, nameof(values));
 
             if (_amountLookup.TryGetValue(currency, out decimal existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 _amountLookup[currency] = existingAmount + value.Amount;
@@ -135,7 +135,7 @@ public void Add(Money value)
     {
         var currency = value.CurrencyOrDefault;
 
-        if (currency == null)
+        if (currency is null)
             return;
 
         EnsureCurrencyAllowed(currency, nameof(value));
@@ -232,7 +232,7 @@ public int RemoveAll(IEnumerable<Currency> currencies)
                 count++;
         }
 
-        if (disallowedCurrencies != null)
+        if (disallowedCurrencies is not null)
             ThrowCurrenciesDisallowed(disallowedCurrencies, nameof(currencies));
 
         return count;
@@ -252,7 +252,7 @@ public int RemoveAll(Func<Money, bool> predicate)
             }
         }
 
-        if (currenciesToRemove != null)
+        if (currenciesToRemove is not null)
         {
             foreach (var currency in currenciesToRemove)
             {
@@ -271,7 +271,7 @@ public int RemoveAll(Func<Money, bool> predicate)
     /// <inheritdoc cref="IMoneySet.RoundToCurrencyDigits(MidpointRounding)"/>
     public void RoundToCurrencyDigits(MidpointRounding mode)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         List<KeyValuePair<Currency, decimal>> updatedEntries = null;
@@ -287,7 +287,7 @@ public void RoundToCurrencyDigits(MidpointRounding mode)
             }
         }
 
-        if (updatedEntries == null)
+        if (updatedEntries is null)
             return;
 
         foreach (var entry in updatedEntries)
@@ -301,7 +301,7 @@ public void SetValue(Money value)
     {
         var currency = value.CurrencyOrDefault;
 
-        if (currency == null)
+        if (currency is null)
             return;
 
         SetAmount(value.Amount, currency);
@@ -363,7 +363,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
         bool ignoreZeroAmounts;
         int count;
 
-        if (format != null && format.StartsWith('!'))
+        if (format is not null && format.Length > 0 && format[0] is '!')
         {
             format = format[1..];
             ignoreZeroAmounts = true;
@@ -375,7 +375,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
             count = Count;
         }
 
-        if (count == 0)
+        if (count is 0)
             return string.Empty;
 
         var sb = new StringBuilder(count * 8);
@@ -383,7 +383,7 @@ public string ToString(string? format, IFormatProvider? formatProvider = null)
 
         foreach (var value in this)
         {
-            if (ignoreZeroAmounts && value.Amount == 0)
+            if (ignoreZeroAmounts && value.Amount is 0)
                 continue;
 
             if (first)
@@ -413,7 +413,7 @@ int GetNonZeroCount()
     /// <inheritdoc cref="IMoneySet.TransformValues(Func{Money, decimal})"/>
     public void TransformValues(Func<Money, decimal> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         // TODO: Optimize if no values change.
@@ -432,7 +432,7 @@ public void TransformValues(Func<Money, decimal> transform)
     /// <inheritdoc cref="IMoneySet.TransformValues(Func{Money, decimal?})"/>
     public void TransformValues(Func<Money, decimal?> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         // TODO: Optimize if no values change.
@@ -455,7 +455,7 @@ public void TransformValues(Func<Money, decimal?> transform)
     /// <inheritdoc cref="IMoneySet.TransformAmounts(Func{decimal, decimal})"/>
     public void TransformAmounts(Func<decimal, decimal> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         // TODO: Optimize if no values change.
@@ -475,7 +475,7 @@ public void TransformAmounts(Func<decimal, decimal> transform)
     /// <inheritdoc cref="IMoneySet.TransformAmounts(Func{decimal, decimal?})"/>
     public void TransformAmounts(Func<decimal, decimal?> transform)
     {
-        if (Count == 0)
+        if (Count is 0)
             return;
 
         // TODO: Optimize if no values change.
@@ -502,14 +502,14 @@ public int TrimZeroAmounts()
 
         foreach (var kvp in _amountLookup)
         {
-            if (kvp.Value == 0)
+            if (kvp.Value is 0)
             {
                 currenciesToRemove ??= [];
                 currenciesToRemove.Add(kvp.Key);
             }
         }
 
-        if (currenciesToRemove != null)
+        if (currenciesToRemove is not null)
         {
             foreach (var currency in currenciesToRemove)
             {
@@ -578,7 +578,7 @@ private void AddRangeInternal(IEnumerable<Money> values, bool ensureCurrenciesIn
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             if (ensureCurrenciesInRegistry && !_registry.Contains(currency))
@@ -590,7 +590,7 @@ private void AddRangeInternal(IEnumerable<Money> values, bool ensureCurrenciesIn
 
             if (_amountLookup.TryGetValue(currency, out decimal existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 _amountLookup[currency] = existingAmount + value.Amount;
@@ -601,7 +601,7 @@ private void AddRangeInternal(IEnumerable<Money> values, bool ensureCurrenciesIn
             }
         }
 
-        if (disallowedCurrencies != null)
+        if (disallowedCurrencies is not null)
             ThrowCurrenciesDisallowed(disallowedCurrencies, nameof(values));
     }
 
@@ -613,7 +613,7 @@ private void SubtractRangeInternal(IEnumerable<Money> values, bool ensureCurrenc
         {
             var currency = value.CurrencyOrDefault;
 
-            if (currency == null)
+            if (currency is null)
                 continue;
 
             if (ensureCurrenciesInRegistry && !_registry.Contains(currency))
@@ -625,7 +625,7 @@ private void SubtractRangeInternal(IEnumerable<Money> values, bool ensureCurrenc
 
             if (_amountLookup.TryGetValue(currency, out decimal existingAmount))
             {
-                if (value.Amount == 0)
+                if (value.Amount is 0)
                     continue;
 
                 _amountLookup[currency] = existingAmount - value.Amount;
@@ -636,7 +636,7 @@ private void SubtractRangeInternal(IEnumerable<Money> values, bool ensureCurrenc
             }
         }
 
-        if (disallowedCurrencies != null)
+        if (disallowedCurrencies is not null)
             ThrowCurrenciesDisallowed(disallowedCurrencies, nameof(values));
     }
 
diff --git a/Source/Singulink.Globalization.Currency/Utilities/CultureInfoExtensions.cs b/Source/Singulink.Globalization.Currency/Utilities/CultureInfoExtensions.cs
index 03bfdf5..12abe04 100644
--- a/Source/Singulink.Globalization.Currency/Utilities/CultureInfoExtensions.cs
+++ b/Source/Singulink.Globalization.Currency/Utilities/CultureInfoExtensions.cs
@@ -8,7 +8,7 @@ internal static class CultureInfoExtensions
     /// </summary>
     public static CultureInfo? GetNeutralCulture(this CultureInfo culture)
     {
-        if (culture == null)
+        if (culture is null)
             throw new ArgumentNullException(nameof(culture));
 
         while (true)
@@ -18,7 +18,7 @@ internal static class CultureInfoExtensions
 
             culture = culture.Parent;
 
-            if (culture == null)
+            if (culture is null)
                 return null;
         }
     }
diff --git a/Tests/Singulink.Globalization.Currency.NetStandardTests/Singulink.Globalization.Currency.NetStandardTests.csproj b/Tests/Singulink.Globalization.Currency.NetStandardTests/Singulink.Globalization.Currency.NetStandardTests.csproj
new file mode 100644
index 0000000..8267505
--- /dev/null
+++ b/Tests/Singulink.Globalization.Currency.NetStandardTests/Singulink.Globalization.Currency.NetStandardTests.csproj
@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net481</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="..\Singulink.Globalization.Currency.Tests\MoneyTests\CompareTo.cs" Link="MoneyTests\CompareTo.cs" />
+    <Compile Include="..\Singulink.Globalization.Currency.Tests\MoneyTests\Operators.cs" Link="MoneyTests\Operators.cs" />
+    <Compile Include="..\Singulink.Globalization.Currency.Tests\MoneyTests\RoundToCurrencyDigits.cs" Link="MoneyTests\RoundToCurrencyDigits.cs" />
+    <Compile Include="..\Singulink.Globalization.Currency.Tests\MoneyTests\ToString.cs" Link="MoneyTests\ToString.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\Source\Singulink.Globalization.Currency\Singulink.Globalization.Currency.csproj" />
+  </ItemGroup>
+  <ItemGroup>
+    <Folder Include="MoneyTests\" />
+  </ItemGroup>
+</Project>
diff --git a/Tests/Singulink.Globalization.Currency.NetStandardTests/Usings.cs b/Tests/Singulink.Globalization.Currency.NetStandardTests/Usings.cs
new file mode 100644
index 0000000..6d97b50
--- /dev/null
+++ b/Tests/Singulink.Globalization.Currency.NetStandardTests/Usings.cs
@@ -0,0 +1,4 @@
+global using System.Collections.Immutable;
+global using Microsoft.VisualStudio.TestTools.UnitTesting;
+global using PrefixClassName.MsTest;
+global using Shouldly;
\ No newline at end of file