C# is 运算符

is 运算符并不是说明对象是某种类型的一种方式，而是可以检查对象是否是给定的类型，或者是否可以转换为给定的类型，如果是，这个运算符就返回true。
is 运算符的语法如下：

<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，或者它封箱到该类型中，则结果为true。
• 如果<type>是一个接口类型，而<operand>也是该类型，或者它实现了该接口的类型，则结果为true。
• 如果<type>是一个值类型，而<operand>也是该类型，或者它被拆箱到该类型中，则结果为true。

实例

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace MySpace{
    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 be 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("\nAnalyzing ClassB type variable:");
            check.Check(try2);
            Console.WriteLine("\nAnalyzing ClassC type variable:");
            check.Check(try3);
            Console.WriteLine("\nAnalyzing ClassD type variable:");
            check.Check(try4);
            Console.WriteLine("\nAnalyzing MyStruct type variable:");
            check.Check(try5);
            Console.WriteLine("\nAnalyzing boxed MyStruct type variable:");
            check.Check(try6);
            Console.ReadKey();
        }
    }
}

执行结果如下：