Mark or set encoding param in StreamReader ctor to be nullable

[eriawan]

Fixes #106236

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[eriawan]

@jozkee please review

cc @rameel

[lilinus]

Should the string path constructors also be modified to allow null (similar to #106658, as discussed in #2376 (comment))? I.e. the ctors below:

public StreamReader(string path, System.Text.Encoding encoding)
public StreamReader(string path, System.Text.Encoding encoding, bool detectEncodingFromByteOrderMarks)
public StreamReader(string path, System.Text.Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize)
public StreamReader(string path, System.Text.Encoding encoding, bool detectEncodingFromByteOrderMarks, System.IO.FileStreamOptions options)

Also; are there any tests that could be modified to verify null encoding works (and acts as UTF8)?

[rameel]

Yes, as @lilinus mentioned, the constructors that accept path and encoding parameters also need to be aligned with the Stream-based constructors, similar to how it was done for StreamWriter.

[eriawan]

Yes, as @lilinus mentioned, the constructors that accept path and encoding parameters also need to be aligned with the Stream-based constructors, similar to how it was done for StreamWriter.

thanks for the feedback! sure, I'm gong to update now.

[eriawan]

@lilinus @rameel

Done updating the ccror with the string path as well.

@jozkee
Could you please review?

[eriawan]

Ok, I also have done refactoring the test of StreamReader's constructor as well.