“根据定义，所有的值类型都必须从System.ValueType派生，所有的枚举都从System.Enum抽象类型中派生，后者又从System.ValueType派生的”                               -------摘自《CLR VIA C#》；

可以通过查找MSDN

测试代码：

 class Program

    {

        static void Main(string[] args)

        {

            Program p = new Program();

            int m = 1;

            Console.WriteLine("int m=1");

            p.function(m);

            double n = 2.44;

            Console.WriteLine("double n = 2.44");

            p.function(n);

            string x = "dasdas";

            Console.WriteLine("string x");

            p.function(x);

            M mm = new M();

            Console.WriteLine("M为结构体");

            p.function(mm);

            Console.WriteLine("Program p ");

            p.function(p);

            Console.ReadLine();

        }

        public void function(Object o)

        {

          if (o.GetType().IsValueType)

                Console.WriteLine( "类型:" + o + "为值类型");

            else

               Console.WriteLine( "类型:" +o + "为引用类型");

        }

    }

    public struct M

    {

        int x;

        int y;

    }

输出结果：