Question

If anyone has a better title, let me know.

I made a DisposeHelper so instead of this:

private Something _thing;

void Dispose()
{
    if(_thing != null)
    {
        _thing.Dispose();
        _thing = null;
    }
}

… i could do this:

private Something _thing;

void Dispose()
{
    DiposeHelper.Dipose(ref _thing);
}

But apparently I can’t feed DisposeHelper.Dispose an IDisposable as a reference, unless I cast Something as IDisposable, like so:

private Something _thing;

void Dispose()
{
    IDisposable d = _thing;
    DiposeHelper.Dipose(ref d);
}

…which would mean it doesn’t then nullify the original field.

Here’s a more abstract example. DoThis works, DoThat doesn’t:

public class Test
{
    public Test()
    {
        Something o = new Something();

        DoThis(o);

        DoThat(ref o);
    }

    private void DoThis(IFoo obj) { }

    private void DoThat(ref IFoo obj) { }
}

public class Something : IFoo { }

public interface IFoo { }

Why can’t I do it?

Answer 1

I don’t know the technical reason as to why you can’t.

This works, however:

var o = new Something();
DoThat(ref o);

private void DoThat<T>(ref T obj) where T : class, IFoo { 
    obj = null;
}