delegates-basics-example.cs

namespace DelegateLearning
{
    public delegate int MathematicalOperationDelegate(int x, int y); //declare
 
    public enum MathematicalOperation
    {
      Add,
      Substract,
      Multiply,
      Divide
    }
 
    class DelegateLearning
    {
        private readonly MathematicalOperationDelegate _mathematicalOperationDelegate;
 
        public DelegateLearning(MathematicalOperation operation)
        {
            switch (operation)
            {
                case MathematicalOperation.Add:
                    _mathematicalOperationDelegate += new MathematicalOperationDelegate(AddOperationTarget); //Adding to invocation list
                    break;
 
                case MathematicalOperation.Substract:
                    _mathematicalOperationDelegate += new MathematicalOperationDelegate(SubOperationTarget); //Adding to invocation list
                    break;
 
                case MathematicalOperation.Multiply:
                    _mathematicalOperationDelegate += new MathematicalOperationDelegate(MultiplyOperationTarget); //Adding to invocation list
                    break;
 
                case MathematicalOperation.Divide:
                    _mathematicalOperationDelegate += new MathematicalOperationDelegate(DivideOperationTarget); //Adding to invocation list.
                    break;
            }
        }
 
        public int PerformMathematicalOperation(int x, int y , MathematicalOperation operation)
        {
            int result = 0;
            if (_mathematicalOperationDelegate != null)
            {
                result = _mathematicalOperationDelegate(x, y); //Invoke
                Console.WriteLine( "Result : " + result);
            }
 
            return result;
        }
 
        private int AddOperationTarget(int x, int y)
        {
            return x + y;
        }
 
        private int SubOperationTarget(int x, int y)
        {
            return x - y;
        }
 
        private int MultiplyOperationTarget(int x, int y)
        {
            return x * y;
        }
 
        private int DivideOperationTarget(int x, int y)
        {
            return x / y;
        }
    }
 
}