Delegates in C#

Delegates in C# are used to hold a reference to a method.

public delegate int PerformCalculation(int x, int y);

Above, you can see the definition of a delegate. It is used to point to a method which returns integer and takes in two integer parameters.

Let's create two methods which are compatible with this delegate.

    private static int Add(int x, int y)
    {
        Console.WriteLine(x + y);
        return x + y;
    }

    private static int Subtract(int x, int y)
    {
        Console.WriteLine(x - y);
        return x - y;
    }

Inside of the Main method we'll define two delegates, both of type PerformCalculation, point them to the Add and Subtract methods and invoke them.

    public static void Main()
    {
        PerformCalculation addCalculation = Add;
        PerformCalculation subtractCalculation = Subtract;

        addCalculation(1, 2);
        subtractCalculation(2, 1);
    }

We can also use a single delegate to point to multiple methods and invoke them all at once.

        PerformCalculation allCalculations = addCalculation + subtractCalculation;
        allCalculations(2, 1);