}

严格求值策略：首先定义一个返回Int的方法

        static int DoSomeThing()

        {

            Console.WriteLine("DoSomeThing Function Excuted");

            return 7;

        }

static void Stricteva luation(bool flag, int dsVal)

        {

            if (flag)

                Console.WriteLine("dsVal result value is {0}", dsVal);

            Console.WriteLine("Done!");

        }

调用：Stricteva luation(false, DoSomeThing());

输出：

DoSomeThing Function Excuted

Done!

虽然flag为false，但是DoSomeThing还是被执行了，如何改变？

将第二个参数改成方法：

static void Lazyeva luation(bool flag,Func<int> dsthing)

        {

            if (flag)

                Console.WriteLine("dsthing result value is {0}", dsthing());

            Console.WriteLine("Done!");

        }

调用：Stricteva luation(false, DoSomeThing);

如果flag为true,并且其中调用两次，那么DoSomeThing就会被执行两次。再次修改

static void Lazyeva luationEx(bool flag, Func<int> dsthing)

        {

            Lazy<int> lzDshting = new Lazy<int>(dsthing);

            if (flag)

      Console.WriteLine("dsthing square result value is {0}", lzDshting.Value * lzDshting.Value);

            Console.WriteLine("Done!");

        }

参考 http://www.cnblogs.com/yaozhenfa/category/652982.html