C#is运算符的作用

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:

 1 namespace Chapter11
 2 {
 3     class Checker
 4     {
 5         public void Check(object param1)
 6         {
 7             if (param1 is ClassA)
 8                 Console.WriteLine("Variable can be converted to ClassA");
 9             else
10                 Console.WriteLine("Variable can‘t be converted to ClassA.");
11
12             if (param1 is IMyInterface)
13                 Console.WriteLine("Variable can be converted to IMyInterface.");
14             else
15                 Console.WriteLine("Variable can‘t converted to IMyInterface.");
16
17             if (param1 is MyStruct)
18                 Console.WriteLine("Variable can be converted to MyStruct.");
19             else
20                 Console.WriteLine("Variable can‘t be converted to MyStruct.");
21         }
22     }
23     interface IMyInterface
24     { }
25     class ClassA : IMyInterface
26     { }
27     class ClassB :IMyInterface
28     { }
29
30     class ClassC
31     { }
32
33     class classD : ClassA
34     { }
35
36     struct MyStruct : IMyInterface
37     { }
38     class Program
39     {
40         static void Main(string[] args)
41         {
42             Checker check = new Checker();
43             ClassA try1 = new ClassA();
44             ClassB try2 = new ClassB();
45             ClassC try3 = new ClassC();
46             classD try4 = new classD();
47             MyStruct try5 = new MyStruct();
48             object try6 = try5;
49             Console.WriteLine("Analyzing ClassA type variable:");
50             check.Check(try1);
51             Console.WriteLine("Analyzing ClassB type variable:");
52             check.Check(try2);
53             Console.WriteLine("Analyzing ClassC type variable:");
54             check.Check(try3);
55             Console.WriteLine("Analyzing ClassD type variable:");
56             check.Check(try4);
57             Console.WriteLine("Analyzing MyStruct type variable:");
58             check.Check(try5);
59             Console.WriteLine("Analyzing boxed MyStruct type variable:");
60             check.Check(try6);
61             Console.ReadKey();
62         }
63     }
64 }