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How to declare and instantiate Delegates in C#?
C# delegates are similar to pointers to functions, in C or C++. A delegate is a reference type variable that holds the reference to a method. The reference can be changed at runtime.
Syntax for declaring Delegates −
delegate <return type> <delegate-name> <parameter list>
Let us now see how to instantiate delegates in C#.
Once a delegate type is declared, a delegate object must be created with the new keyword and be associated with a particular method. When creating a delegate, the argument passed to the new expression is written similar to a method call, but without the arguments to the method.
public delegate void printString(string s); ... printString ps1 = new printString(WriteToScreen); printString ps2 = new printString(WriteToFile);
The following is an example to declare and instantiate delegates in C# −
Example
using System;
delegate int NumberChanger(int n);
namespace DelegateAppl {
class TestDelegate {
static int num = 10;
public static int AddNum(int p) {
num += p;
return num;
}
public static int MultNum(int q) {
num *= q;
return num;
}
public static int getNum() {
return num;
}
static void Main(string[] args) {
//create delegate instances
NumberChanger nc1 = new NumberChanger(AddNum);
NumberChanger nc2 = new NumberChanger(MultNum);
//calling the methods using the delegate objects
nc1(25);
Console.WriteLine("Value of Num: {0}", getNum());
nc2(5);
Console.WriteLine("Value of Num: {0}", getNum());
Console.ReadKey();
}
}
}Output
Value of Num: 35 Value of Num: 175
Updated on: 20-Jun-2020
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