function delegate c# code example

Example 1: C# delegate

using System;

	public class CargoAircraft
    {
      	// Create a delegate type (no return no arguments)
        public delegate void CheckQuantity();
		// Create an instance of the delegate type
        public CheckQuantity ProcessQuantity;

        public void ProcessRequirements()
        {
          // Call the instance delegate
          // Will invoke all methods mapped
            ProcessQuantity();
        }
    }

    public class CargoCounter
    {
        public void CountQuantity() { }
    }

    class Program
    {
        static void Main(string[] args)
        {
            CargoAircraft cargo = new CargoAircraft();
            CargoCounter cargoCounter = new CargoCounter();
			
          	// Map a method to the created delegate
            cargo.ProcessQuantity += cargoCounter.CountQuantity;
          	
          	// Will call instance delegate invoking mapped methods
            cargo.ProcessRequirements();
        }
    }
}

Example 2: delegate function c#

// Create the Delgate method.
public delegate void Del(string message);

// Create a method for a delgate.
public static void DelegateMethod(string message)
{
  Console.WriteLine(message);
}

// Instatiate the delegate.
Del hadler = DelegateMethod;

// Call the delegate.
hadler("Hello World");

// Output
// Hello World

Example 3: c# func

using System;
using System.Collections.Generic;
using static System.Console;
namespace CSFlow.Delegates.Others
{
    public class ActionFunc
    {

        public static void Run ()
        {
            // Example of : Action
            // Use action when a mathod return void
            Action<string> display = new Action<string>(DisplayMessage);
            display("Calculate Discount :");

            // Example of : Func
            // Use action when a mathod return value
            Func<double, double> discount = new Func<double, double>(Discount);
            display(discount(12.5).ToString());

            List<Customer> custList = new List<Customer>();
            custList.Add(new Customer { Id = 1, FirstName = "Joydip", LastName = "Kanjilal", State = "Telengana", City = "Hyderabad", Address = "Begumpet", Country = "India" });
            custList.Add(new Customer { Id = 2, FirstName = "Steve", LastName = "Jones", State = "OA", City = "New York", Address = "Lake Avenue", Country = "US" });
            custList.Add(new Customer { Id = 3, FirstName = "Sefat", LastName = "Anam", State = "OSA", City = "New York", Address = "Manhatten", Country = "US" });

            // Example of : Predicate
            // Use Predicate for search data
            Predicate<Customer> FindAddress = customer => customer.Address == "Manhatten";

            Customer searchData = custList.Find(FindAddress);

            display($"{searchData?.FirstName} {searchData?.LastName} From - {searchData?.City} ");

            ReadKey();
        }

        static void DisplayMessage (string message)
        {
            WriteLine(message);
        }

        static double Discount (double money)
        {
            return money * .5;
        }

        class Customer
        {
            public int Id { get; set; }
            public string FirstName { get; set; }
            public string LastName { get; set; }
            public string Address { get; set; }
            public string City { get; set; }
            public string State { get; set; }
            public string Country { get; set; }
        }
    }
}