[API Proposal]: Add FileStream.DefaultBufferSize

[Neme12]

Background and motivation

FileStream has a few constructors with a non-optional bufferSize, and there is currently no way to pass a value (either 0 or -1) to get the default behavior, as in constructors that do not take it. That's why I propose just exposing the DefaultBufferSize so that we don't have to hardcode 4096 everywhere, because that is the current default.

API Proposal

namespace System.IO;

public partial class FileStream : Stream
{
	public const int DefaultBufferSize = 4096;
    // or
    public static int DefaultBufferSize { get; }
}

API Usage

using var fileStrem = new FileStream(
	fileHandle,
	FileAccess.Read,
	FileStream.DefaultBuffersize,
	isAsync: true);

Alternative Designs

No response

Risks

No response

[huoyaoyuan]

This should be a property instead of constant, since the optimal behavior can change between versions.

[Neme12]

This should be a property instead of constant, since the optimal behavior can change between versions.

You're right, I thought it was already baked in as a constant in some parameter as a default value, but looking now, it doesn't seem to be. I updated the proposal.