C# is运算符的作用（转）

原文链接：https://www.cnblogs.com/cheny3636/p/4995784.html

is运算符的含义:检查对象是不是给定类型,或者是否可以转换为给定类型,如果是,这个运算符就返回True.

is运算符的语法:<operand> is <type>

这个表达式的结果如下:如果<type>是一个类类型,而<operand>也是该类型,或者它继承了该类型,或者它可以封箱到该类型中,则结果返回True.

                             如果<type>是一个接口类型,而<operand>也是该类型,或者它是实现该接口的类型,则结果返回True.

　　　　　　　　　　 如果<type>是一个值类型,而<operand>也是该类型,或者它可以拆箱到该类型中,则返回True.

is实例:

namespace Chapter11
{
    class Checker
    {
        public void Check(object param1)
        {
            if (param1 is ClassA)
                Console.WriteLine("Variable can be converted to ClassA");
            else
                Console.WriteLine("Variable can't be converted to ClassA.");

            if (param1 is IMyInterface)
                Console.WriteLine("Variable can be converted to IMyInterface.");
            else
                Console.WriteLine("Variable can't converted to IMyInterface.");

            if (param1 is MyStruct)
                Console.WriteLine("Variable can be converted to MyStruct.");
            else
                Console.WriteLine("Variable can't be converted to MyStruct.");
        }
    }
    interface IMyInterface
    { }
    class ClassA : IMyInterface
    { }
    class ClassB :IMyInterface
    { }

    class ClassC
    { }

    class classD : ClassA
    { }

    struct MyStruct : IMyInterface
    { }
    class Program
    {
        static void Main(string[] args)
        {
            Checker check = new Checker();
            ClassA try1 = new ClassA();
            ClassB try2 = new ClassB();
            ClassC try3 = new ClassC();
            classD try4 = new classD();
            MyStruct try5 = new MyStruct();
            object try6 = try5;
            Console.WriteLine("Analyzing ClassA type variable:");
            check.Check(try1);
            Console.WriteLine("Analyzing ClassB type variable:");
            check.Check(try2);
            Console.WriteLine("Analyzing ClassC type variable:");
            check.Check(try3);
            Console.WriteLine("Analyzing ClassD type variable:");
            check.Check(try4);
            Console.WriteLine("Analyzing MyStruct type variable:");
            check.Check(try5);
            Console.WriteLine("Analyzing boxed MyStruct type variable:");
            check.Check(try6);
            Console.ReadKey();
        }
    }
}