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What is the use of "is" keyword in C#?
The "is" keyword is used to check if an object can be casted to a specific type. The return type of the operation is Boolean.
Example
using System;
namespace DemoApplication{
class Program{
static void Main(){
Employee emp = new PermanentEmployee{
ID = 1,
Name = "Martin"
};
// Returns true as the derived type can be converted to base type.
if (emp is Employee){
Console.WriteLine(emp.Name + " is Employee");
}
else{
Console.WriteLine(emp.Name + " is not Employee");
}
//Returns true, as the actual object is of type PermanentEmployee.
if (emp is PermanentEmployee){
Console.WriteLine(emp.Name + " is PermanentEmployee");
}
else{
Console.WriteLine(emp.Name + " is not PermanentEmployee");
}
//Returns false, as PermanentEmployee object cannot be converted to
//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; }
}
}
Updated on: 04-Aug-2020
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