C# 中"is"关键字有什么用?
csharpserver side programmingprogramming更新于 2025/10/2 13:07:17
"is" 关键字用于检查对象是否可以转换为特定类型。该操作的返回类型为布尔值。
示例
using System;
namespace DemoApplication{
class Program{
static void Main(){
Employee emp = new PermanentEmployee{
ID = 1,
Name = "Martin"
};
// 返回 true，因为派生类型可以转换为基类型。
if (emp is Employee){
Console.WriteLine(emp.Name + " is Employee");
}
else{
Console.WriteLine(emp.Name + " is not Employee");
}
//返回 true，因为实际对象属于 PermanentEmployee 类型.
if (emp is PermanentEmployee){
Console.WriteLine(emp.Name + " is PermanentEmployee");
}
else{
Console.WriteLine(emp.Name + " is not PermanentEmployee");
}
//返回 false，因为 PermanentEmployee 对象无法转换为
//ContractEmployee。
if (emp is ContractEmployee){
Console.WriteLine(emp.Name + " is ContractEmployee");
}
else{
Console.WriteLine(emp.Name + " is not ContractEmployee");
}
}
}
class Employee{
public int ID { get; set; }
public string Name { get; set; }
}
class PermanentEmployee : Employee{
public int AnnualSalary { get; set; }
}
class ContractEmployee : Employee{
public int HourlySalary { get; set; }
}
}
