C# Delegate Sample

New developers often ask me about C# delegate, as they got a bit confused about the basic concept and specially maximum of the reference contains and discussed from an advanced view. Well I think delegate is really simple, when you grab it's basic idea.

So what is delegate?

Basically it is similar like the old "C" age function pointer, where functions can be assigned like a variable and called in the run time based on dynamic conditions. C# delegate is the smarter version of function pointer which helps software architects a lot, specially while utilizing design patterns.

At first, a delegate is defined with a specific signature (return type, parameter type and order etc). To invoke a delegate object, one or more methods are required with the EXACT same signature. A delegate object is first created similar like a class object created. The delegate object will basically hold a reference of a function. The function will then can be called via the delegate object.

Sounds easy? If not lets have a look in the code snippets below.

1. Defining the delegate



public delegate int Calculate (int value1, int value2);

2. Creating methods which will be assigned to delegate object



//a method, that will be assigned to delegate objects
//having the EXACT signature of the delegate
public int add(int value1, int value2)
{
return value1 + value2;
}
//a method, that will be assigned to delegate objects
//having the EXACT signature of the delegate
public int sub( int value1, int value2)
{
return value1 - value2;
}

3. Creating the delegate object and assigning methods to those delegate objects



//creating the class which contains the methods
//that will be assigned to delegate objects
MyClass mc = new MyClass();

//creating delegate objects and assigning appropriate methods
//having the EXACT signature of the delegate
Calculate add = new Calculate(mc.add);
Calculate sub = new Calculate(mc.sub);

4. Calling the methods via delegate objects



//using the delegate objects to call the assigned methods
Console.WriteLine("Adding two values: " + add(10, 6));
Console.WriteLine("Subtracting two values: " + sub(10,4));