In this blog I shall demonstrate how to use the Func Delegate in .Net framework.

Before going through this article I recommend you get some knowledge of Delegates. There are many articles and blogs in c-sharpcorner.com.

Step 1: Create a class named Customer.

using System;

using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace FuncDelegates

{
public class Customer
{
public int ID { get; set; }
public string Name { get; set; }
public int Points { get; set; }
}
}

Step 2: Create a class named Utility as shown below.

using System;

using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace FuncDelegates

{
public class Utility
{
static List<Customer> CustomerList = null;
/// <summary>
///
/// </summary>
/// <param name="lstCustomer"></param>
/// <param name="custDelegate">
/// This is a Func delegate which takes an input string and outputs a boolean value.
/// </param>
/// <returns></returns>
public static List<Customer> GetEligibleCustomers(List<Customer> lstCustomer,Func<Customer,bool> custDelegate)
{
CustomerList = new List<Customer>();
foreach (Customer cust in lstCustomer)
{
// for each customer the func delegate in invoked to check whether he/she satifies the condition passed from client.
if (custDelegate(cust))
{
CustomerList.Add(cust);
}
}
return CustomerList;
}
}
}

The function GetEligibleCustomers has got 2 parameters.

  1. List<Customer>
  2. Func<Customer,bool>

The second parameter is of Func delegate type. This delegate accepts Customer as input and returns a Boolean value.

In my previous article I have created a delegate and that delegate was used in code.

For reference please go through the article Delegates in Actual Projects.

In this example I have used the predefined Func delegate in .Net framework.

Step 3: Main Class

using System;

using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace FuncDelegates

{
class Program
{
static List<Customer> customerList=null;
static void Main(string[] args)
{

customerList = new List<Customer>();

Customer cust1 = new Customer { ID = 1, Name = "Praveen", Points = 1000 };
Customer cust2 = new Customer { ID = 2, Name = "Ajai", Points = 420 };
Customer cust3 = new Customer { ID = 3, Name = "Sabari", Points = 200 };
Customer cust4 = new Customer { ID = 2, Name = "Anju", Points = 660 };
Customer cust5 = new Customer { ID = 2, Name = "Madhav", Points = 600 };
customerList.Add(cust1);
customerList.Add(cust2);
customerList.Add(cust3);
customerList.Add(cust4);
customerList.Add(cust5);

Console.WriteLine("The Customer DataBase....... ");

Console.WriteLine("**********************************************************************");
foreach (var customer in customerList)
{
Console.WriteLine("ID: {0}, Name : {1} , Points {2}", customer.ID, customer.Name, customer.Points);
}
Console.WriteLine("**********************************************************************"); Console.WriteLine("Eligible Customers : Points >500");

Console.WriteLine("**********************************************************************");

var eligibleCustomers = Utility.GetEligibleCustomers(customerList, e => e.Points > 500);

foreach (var cust in eligibleCustomers
{
Console.WriteLine("ID: {0}, Name : {1} , Points {2}", cust.ID, cust.Name, cust.Points);
}
Console.ReadLine();
}
}
}

Please have a look at the highlighted code. The GetEligibleCustomers function accepts 2 parameters.

For each customer in the customer list, the Func delegate is invoked to check whether that customer is an eligible customer or not.

For a better understanding I have uploaded the source code.

Output