ExceptionExtensions.cs

public static class ExceptionExtensions
{
    public static string Details(this Exception exception)
    {
        StringBuilder builder = new StringBuilder();
        builder.AppendLine(exception.Message);

        while (exception.InnerException != null)
        {
            builder.AppendLine(exception.InnerException.Message);
        }

        builder.AppendLine(exception.StackTrace);

        return builder.ToString();
    }
}