C# -将字符串转换为可空的Guid？

public static bool TryParse(string input, out Guid? result);

string str = "123e4567-e89b-12d3-a456-426655440000";
Guid? guid;

if (Guid.TryParse(str, out guid))
{
    Console.WriteLine("转换成功，Guid的值为：" + guid);
}
else
{
    Console.WriteLine("转换失败");
}