Intercepting an exception inside IDisposable.Dispose

Question

In the IDisposable.Dispose method is there a way to figure out if an exception is being thrown?

using (MyWrapper wrapper = new MyWrapper())
{
           


        

Answer 1

This will catch exceptions thrown either directly or inside the dispose method:

try
{
    using (MyWrapper wrapper = new MyWrapper())
    {
        throw new MyException("Bad error.");
    }
}
catch ( MyException myex ) {
    //deal with your exception
}
catch ( Exception ex ) {
    //any other exception thrown by either
    //MyWrapper..ctor() or MyWrapper.Dispose()
}

But this is relying on them using this this code - it sounds like you want MyWrapper to do that instead.

The using statement is just to make sure that Dispose always gets called. It's really doing this:

MyWrapper wrapper;
try
{
    wrapper = new MyWrapper();
}
finally {
    if( wrapper != null )
        wrapper.Dispose();
}

It sounds like what you want is:

MyWrapper wrapper;
try
{
    wrapper = new MyWrapper();
}
finally {
    try{
        if( wrapper != null )
            wrapper.Dispose();
    }
    catch {
        //only errors thrown by disposal
    }
}

I would suggest dealing with this in your implementation of Dispose - you should handle any issues during Disposal anyway.

If you're tying up some resource where you need users of your API to free it in some way consider having a Close() method. Your dispose should call it too (if it hasn't been already) but users of your API could also call it themselves if they needed finer control.