Stream returned in route is disposed twice

[jeremiahpopebiomerieux]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When returning a stream as a file while creating a web API, the stream is disposed twice.

Expected Behavior

The stream should only be disposed once.

Steps To Reproduce

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();
var app = builder.Build();

app.Map("/test", () =>
{
    var stream = new MyStream();
    return Results.File(stream);
});

app.Run();

internal class MyStream : MemoryStream
{
    private int _count;
    protected override void Dispose(bool disposing)
    {
        _count++;
        Console.WriteLine(_count);
        base.Dispose(disposing);
    }
}

I can also reproduce while using FileStreamResult.

Exceptions (if any)

No response

.NET Version

9.0.101

Anything else?

There is no stack trace.

[quails4Eva]

Note, this appears to apply to MVC as well, though might be different code.

From what I can tell, for MVC when returning a FileStreamResult the stream is wrapped in a using in FileStreamResultExecutor, then it calls FileResultHelper.WriteFileAsync via the base class which wraps it in another using

Main reason I noticed is that I'm trying to reduce memory usage with System.IO.RecyclableMemoryStream and it flags the double dispose as a critical error (since disposing returns the stream to the pool.)

[mitchdenny]

Streams can have their Dispose method called multiple times:

https://learn.microsoft.com/en-us/dotnet/api/system.io.stream.dispose?view=net-9.0

https://learn.microsoft.com/en-us/dotnet/standard/garbage-collection/implementing-dispose