Helper method to flatten AggregateException hierarchy into a plain text.

gistfile1.cs

public string GetExceptionLog(Exception exception)
{
    return UnwrapExceptionTextLoop(new StringBuilder(), 0, exception);
}

private string UnwrapExceptionTextLoop(StringBuilder sb, int level, Exception e)
{
    if (e == null)
    {
        return sb.ToString();
    }

    for (int i = 0; i < level; i++)
    {
        sb.Append(">>");
    }

    var aggregate = e as AggregateException;

    sb.AppendFormat("{0} - {1} [{2}] {3}", e.GetType(), aggregate == null ? e.Message : String.Empty, e.StackTrace, Environment.NewLine);

    if (aggregate != null)
    {
        return String.Join(Environment.NewLine,
            aggregate.InnerExceptions.Select(inner => UnwrapExceptionTextLoop(sb, level + 1, inner)));
    }

    return UnwrapExceptionTextLoop(sb, level + 1, e.InnerException);
}