.NET Standard 2.0 support, tests and cleanup

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>
 

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}

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
             }
         }
 
@@ -159,15 +168,15 @@ public string ToString(string? format, CultureInfo? culture = null)
 
         string name;
 
-        if (_localizedNameLookup == null)
+        if (_localizedNameLookup is null)
         {
             name = Name;
         }
         else if (!_localizedNameLookup.TryGetValue(culture.Name, out name))
         {
             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

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;
@@ -25,16 +30,27 @@ 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 = [];
         _currencyLookup = new(StringComparer.OrdinalIgnoreCase);
 
         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;

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
 }