interface implementation

[stevenkobes]

If s has type System.IO.Stream, why does ((IDisposable) s).Dispose()
work while s.Dispose() fails? The error is:

error CS0117: 'System.IO.Stream' does not contain a definition for
'Dispose'

This seems impossible since Stream implements IDisposable.

 

[Nicholas Paldino [.NET/C# MVP]]

It doesn't work because implementers of interfaces don't have to expose
their members publically. The Stream class does not expose the Dispose
method publically, which is why you need the cast.

Hope this helps.

 

[stevenkobes]

It doesn't work because implementers of interfaces don't have to expose
their members publically. The Stream class does not expose the Dispose
method publically, which is why you need the cast.

Really?

class Foo : IDisposable {
protected void Dispose() {}
}

error CS0536: 'Foo' does not implement interface member
'System.IDisposable.Dispose()'. 'Foo.Dispose()' is either static, not
public, or has the wrong return type.

 

[Nicholas Paldino [.NET/C# MVP]]

Yes, really:

class Foo : IDisposable
{
void IDispose.Dispose()
{
}
}

 

[Nicholas Paldino [.NET/C# MVP]]

That should be:

class Foo : IDisposable
{
void IDisposable.Dispose()
{
}
}

 

[stevenkobes]

class Foo : IDisposable
{
void IDisposable.Dispose()
{
}
}

Wow, I didn't know about that syntax. Thanks!