How do I 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 inner exception. I can do this in a while loop:

while (e.InnerException != null)
{
    e = e.InnerException;
}

But I was wondering if there was some one-liner I could use to do this instead.

Answer 1

Oneliner :)

while (e.InnerException != null) e = e.InnerException;

Obviously, you can't make it any simpler.

Answer 2

You could use recursion to create a method in a utility class somewhere.

public Exception GetFirstException(Exception ex)
{
    if(ex.InnerExecption == null) { return ex; } // end case
    else { return GetFirstException(ex.InnerException); } // recurse
}

Use:

try
{
    // some code here
}
catch (Exception ex)
{
    Exception baseException = GetFirstException(ex);
}

The extension method suggested (good idea @dtb)

public static Exception GetFirstException(this Exception ex)
{
    if(ex.InnerExecption == null) { return ex; } // end case
    else { return GetFirstException(ex.InnerException); } // recurse
}

Use:

try
{
    // some code here
}
catch (Exception ex)
{
    Exception baseException = ex.GetFirstException();
}

Answer 3

If you don't know how deep the inner exceptions are nested, there is no way around a loop or recursion.

Of course, you can define an extension method that abstracts this away:

public static class ExceptionExtensions
{
    public static Exception GetInnermostException(this Exception e)
    {
        if (e == null)
        {
            throw new ArgumentNullException("e");
        }

        while (e.InnerException != null)
        {
            e = e.InnerException;
        }

        return e;
    }
}

Answer 4

Sometimes you might have many inner exceptions (many bubbled exceptions). In which case you might want to do:

List<Exception> es = new List<Exception>();
while(e.InnerException != null)
{
   es.add(e.InnerException);
   e = e.InnerException
}

Answer 5

Not quite one line but close:

        Func<Exception, Exception> last = null;
        last = e => e.InnerException == null ? e : last(e.InnerException);