[c#] What is the proper way to display the full InnerException?

buildup on nawfal 's answer.

when using his answer there was a missing variable aggrEx, I added it.

file ExceptionExtenstions.class:

// example usage:
// try{ ... } catch(Exception e) { MessageBox.Show(e.ToFormattedString()); }

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace YourNamespace
{
    public static class ExceptionExtensions
    {

        public static IEnumerable<Exception> GetAllExceptions(this Exception exception)
        {
            yield return exception;

            if (exception is AggregateException )
            {
                var aggrEx = exception as AggregateException;
                foreach (Exception innerEx in aggrEx.InnerExceptions.SelectMany(e => e.GetAllExceptions()))
                {
                    yield return innerEx;
                }
            }
            else if (exception.InnerException != null)
            {
                foreach (Exception innerEx in exception.InnerException.GetAllExceptions())
                {
                    yield return innerEx;
                }
            }
        }


        public static string ToFormattedString(this Exception exception)
        {
            IEnumerable<string> messages = exception
                .GetAllExceptions()
                .Where(e => !String.IsNullOrWhiteSpace(e.Message))
                .Select(exceptionPart => exceptionPart.Message.Trim() + "\r\n" + (exceptionPart.StackTrace!=null? exceptionPart.StackTrace.Trim():"") );
            string flattened = String.Join("\r\n\r\n", messages); // <-- the separator here
            return flattened;
        }
    }
}