Explicit Conversion to IDisposable

Question

I am using some XmlReader and XmlWriter object to do some needed work on strings inside some try...catch blocks.

I know that using the notation using (XmlReader NewReader = XmlReader.Create(...)) is the prefered syntax, but I don't really like that so I am also appending finally blocks and executing NewReader.Close(); and NewWriter.Close();.

However, code analysis is complaining that these objects aren't being disposed, thus forcing me to somehow call Dispose() method.

The problem is that in these classes the Dispose() method is implemented explicitly, so I have to use ((IDisposable)(NewReader)).Dispose(); and ((IDisposable)(NewWriter)).Dispose();.

Are there any drawbacks to this technique?

Answer 1

The C# using statement will always call Dispose for you. It roughtly translates to the following:

XmlReader NewReader = XmlReader.Create(...);
try
{
   // do stuff on NewReader 
}
finally
{
    ((IDisposable)NewReader).Dispose();
}

So wrapping it in finally youself doesn't add any value. Although Close and Dispose are often equivalent, it is not always the case. Because of this FxCop is right, you should always call Dispose and when you do this (or let the using statement do this), there is no reason to call Close manually.