using System;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

        try

        {

            string test = null;

            test.StringToGuid();

        }

        catch (Exception ex)

        {

            Console.WriteLine(ex);

        }

    }

}

    public static class Test

    {

    public static Guid StringToGuid(this string guid)

        {

            Guid newGuid;

            if (string.IsNullOrEmpty(guid)) throw new ArgumentException();

            Guid.TryParse(guid, out newGuid);

            if (result.IsNullOrEmptyGuid()) throw new ArgumentException();

            return newGuid;

        }

    public static bool IsNullOrEmptyGuid(Guid guid)

        {

            return guid == default(Guid) || guid == Guid.Empty;

        }

    }

​

​