There’s something about the using block (that’s been around in C# since its creation, and it’s now a new feature in VB 2005) that I never quite got it.
The using block is supposed to always call the Disposable method on a object automatically at the end of the block. However, what if something bad happen on that code and an exception is thrown? For instance let’s say we have the following class:
class MyClass : IDisposable
{
#region IDisposable Members
public void Dispose()
{
Console.WriteLine("Disposing…");
}
#endregion
}
And then we use that class like so:
using (MyClass foo = new MyClass())
{
throw new Exception("Forcing an exception…");
}
{
throw new Exception("Forcing an exception…");
}
In such case, the Dispose method never gets called. That means we’d have to wrap that code up in a try/catch/Finally block, and call the Dispose method manually on the Finally block, defeating the purpose of the using block.
For that reason, instead of going that route, I’ve actually just been taking care of that myself, like so:
MyClass foo = null;
try
{
foo = new MyClass();
throw new Exception("Forcing an exception…");
}
catch
{
Console.WriteLine("Catching…");
}
finally
{
Console.WriteLine("Finally…");
if (foo != null)
{
foo.Dispose();
}
}
That way I’m pretty sure that the Dispose method gets called no matter what (provided that the object doesn’t have a null reference).
Maybe somebody could jump in here and give us some insight in case I’m overlooking something here.
Claudio Lassala's Blog 