Unable to call Dispose?

Question

This one has confused me a little... Attempting to dispose of an XmlReader

XmlReader reader = XmlReader.Create(filePath);
reader.Dispose();  

Provides the following error:

'System.Xml.XmlReader.Dispose(bool)' is inaccessible due to its protection level

however the following is fine:

using(XmlReader reader = XmlReader.Create(filePath))
{
}

When I look at the definition in Reflector I can't understand why I can't call Dispose

Implementation of Dispose:

Can anyone point out what I'm missing?

Answer 1

The problem is that XmlReader uses explicit interface implementation to implement IDisposable. So you can write:

XmlReader reader = XmlReader.Create(filePath);
((IDisposable)reader).Dispose();

However, I'd strongly suggest using a using statement anyway. It should be very rare that you call Dispose explicitly, other than within another Dispose implementation.

EDIT: As noted, this is "fixed" in .NET 4.5, in that it exposes a public parameterless Dispose method as of .NET 4.5 as well as the explicit interface implementation. So presumably you're compiling against .NET 4.0 or earlier (perhaps .NET 2.0 given your tags) but using Reflector against .NET 4.5?

Answer 2

using(XmlReader reader = XmlReader.Create(filePath))
{
   foo(reader);
}

is exactly equivalent to

XmlReader reader = XmlReader.Create(filePath);
try 
{
   code(reader);
} 
finally
{
   if(reader != null)
     ((IDisposable)reader).Dispose();
}

The most likely thing is that you haven't posted all of your code - perhaps someone else is calling Dispose() on your object as well, causing an exception in the second call to Dispose()?