Dispose of some disposables, #265, #615

[paulirwin]

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Disposes of some IDisposable objects that are not properly cleaned up.

Fixes #615
Partial #265

Description

This adds using statements to clean up some disposable objects where it's possible to do so, after a review of our codebase with CA2000 code analysis warnings on, where the objects were determined to not "leak" via fields, return values, or the like. This also fixes two FileStream leaks in demo code, #615.

Note that CA2000 is way too noisy to leave on, as there are literally hundreds of "violations" that would make our code a mess with #pragma suppressions. The Java upstream code is perhaps a little loose with keeping track of ICloseable lifetimes, but we have to match that in most cases. The cases fixed here were just ones where the object lifetime did not escape the method and it was safe to do so.

[NightOwl888]

Thanks for the PR.

I agree that keeping CA2000 on would not be a great idea. That being said, some of these had real underlying issues, but others also inadvertently cause Dispose() to be called multiple times on the underlying stream. What is your estimate on how thorough this review is?

IDisposable is a leaky abstraction, so when it is implemented in a base class all of the subclasses automatically inherit it even if they don't require it. I think the Lucene team is pretty thorough about declaring most of them properly, but there are some exceptions to this. It would be good to catch those exceptions before the release, if possible.