Find the inner-most exception without using a while loop?

Question

When C# throws an exception, it can have an inner exception. What I want to do is get the inner-most exception, or in other words, the leaf exception that doesn\'t have an i

Answer 1

You have to loop, and having to loop, it's cleaner to move the loop into a separate function.

I created an extension method to deal with this. It returns a list of all of the inner exceptions of the specified type, chasing down Exception.InnerException and AggregateException.InnerExceptions.

In my particular problem, chasing down the inner exceptions was more complicated than usual, because the exceptions were being thrown by the constructors of classes that were being invoked through reflection. The exception we were catching had an InnerException of type TargetInvocationException, and the exceptions we actually needed to look at were buried deep in the tree.

public static class ExceptionExtensions
{
    public static IEnumerable innerExceptions(this Exception ex)
        where T : Exception
    {
        var rVal = new List();

        Action lambda = null;
        lambda = (x) =>
        {
            var xt = x as T;
            if (xt != null)
                rVal.Add(xt);

            if (x.InnerException != null)
                lambda(x.InnerException);

            var ax = x as AggregateException;
            if (ax != null)
            {
                foreach (var aix in ax.InnerExceptions)
                    lambda(aix);
            }
        };

        lambda(ex);

        return rVal;
    }
}

Usage is pretty simple. If, for example, you want to know if we encountered a

catch (Exception ex)
{
    var myExes = ex.innerExceptions();
    if (myExes.Any(x => x.Message.StartsWith("Encountered my specific error")))
    {
        // ...
    }
}