How to rethrow the inner exception of a TargetInvocationException without losing the stack trace

Question

I have many methods which are calling using Delegate.DynamicInvoke. Some of these methods make database calls and I would like to have the ability to catch a

Answer 1

If you just want to re-throw an inner exception preserving its stack trace, you can do it with a method like this:

public static void Rethrow(this Exception ex)
{
  typeof(Exception).GetMethod("PrepForRemoting",
      BindingFlags.NonPublic | BindingFlags.Instance)
      .Invoke(ex, new object[0]);
  throw ex;
}

This technique is used by Rx (and is exposed by them as an extension method Exception.PrepareForRethrow) and is also used by the Async CTP by its automatic-unwrapping system (without a publicly-exposed API).

Note, however, that this technique is technically unsupported. Hopefully Microsoft will add an official API for this in the future. A suggestion has been opened on Microsoft Connect if you would like to vote for it.

Update: An official API has been added to .NET 4.5: ExceptionDispatchInfo.