Delegate
Delegate
is type safe function pointer. That is, it holds a reference (pointer) to a
function.
The
signature of the Delegate must match the signature of the function,
The
Delegate points to; otherwise you get a compiler error.
This
is the reason Delegates are called as type safe function pointers.
A
Delegate is similar to class. You can create an instance of it, and when you do
so you pass in the function name as a parameter to the delegate constructor,
and it is to this function the delegate will point to.
Delegate
syntax look very much similar to a method with a delegate keyword.
Structures
are value types in case Classes, Interfaces and Delegates are reference types
Application
1
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public delegate void SimpleDelegateMethod(string
FirstName);
public delegate int IntDelegateMethod(int
FirstVal, int SecondVal);
namespace Delegates
{
class DelegatesDemo
{
static void Main(string[] args)
{
// Delegate is type safe function pointer.
// Without Delegates method call
PrintFirstName("Rahul");
DelegatesDemo ObjDelegatesDemo = new
DelegatesDemo();
Console.WriteLine("Sum
without Delegate is {0}", ObjDelegatesDemo.SumOfInteger(7, 5));
Console.WriteLine("===================================================="
+ Environment.NewLine);
// Using delegates method call
SimpleDelegateMethod ObjSimpleDelegateMethod = new
SimpleDelegateMethod(PrintFirstName);
ObjSimpleDelegateMethod("Sagar - Using
Delegates");
IntDelegateMethod ObjIntDelegateMethod = new
IntDelegateMethod(ObjDelegatesDemo.SumOfInteger);
int Sum = ObjIntDelegateMethod(8, 7);
Console.WriteLine("Sum
using Delegate is {0}", Sum);
Console.ReadLine();
}
public static void PrintFirstName(string
strFirstName)
{
Console.WriteLine("First
Name is {0}", strFirstName);
}
public int
SumOfInteger(int a, int
b)
{
int c = a + b;
return c;
}
}
}
Application
2
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace DelegateExample2
{
public delegate bool IsEmployeeApplicableDelegate(Employee employee);
public class Employee
{
public int EmployeeID
{ get; set; }
public string Name { get; set; }
public int Salary { get; set; }
public int Experience
{ get; set; }
public int Grade { get; set; }
public string
Designation { get; set;
}
public static void FindEmployee(List<Employee>
Employees, IsEmployeeApplicableDelegate empDelegate)
{
Console.WriteLine("Below
are the Senior Employees in Organization.");
foreach (Employee emp in
Employees)
{
if (empDelegate(emp))
{
Console.WriteLine(emp.Name);
}
}
}
public static bool IsApplicable(Employee EmployeesList)
{
if (EmployeesList.Grade >= 5)
{
return true;
}
else
{
return false;
}
}
public static List<Employee> CreateEmployee()
{
List<Employee> employee = new List<Employee>();
employee.Add(new Employee() { EmployeeID
= 1, Name = "Avinash", Salary =
5200221, Grade = 4, Designation = "Software
Engineer" });
employee.Add(new Employee() { EmployeeID
= 2, Name = "Pradip", Salary =
6200000, Grade = 5, Designation = "Team
Leader" });
employee.Add(new Employee() { EmployeeID
= 3, Name = "Rajeev", Salary =
7800548, Grade = 6, Designation = "Project
Leader" });
employee.Add(new Employee() { EmployeeID
= 4, Name = "Paresh", Salary =
8700278, Grade = 7, Designation = "vice
President" });
employee.Add(new Employee() { EmployeeID
= 5, Name = "Karna", Salary =
9200232, Grade = 8, Designation = "Sr vice
President" });
employee.Add(new Employee() { EmployeeID
= 6, Name = "Arjun", Salary =
10200271, Grade = 9, Designation = "CEO"
});
employee.Add(new Employee() { EmployeeID
= 7, Name = "Bhishma", Salary =
4278785, Grade = 4, Designation = "Software
Engineer" });
employee.Add(new Employee() { EmployeeID
= 8, Name = "Ram", Salary =
4270231, Grade = 4, Designation = "Software
Engineer" });
employee.Add(new Employee() { EmployeeID
= 9, Name = "Sham", Salary =
3022544, Grade = 3, Designation = "Jr Software
Engineer" });
employee.Add(new Employee() { EmployeeID
= 10, Name = "Santosh", Salary =
2054454, Grade = 3, Designation = "Jr Software
Engineer" });
return employee;
}
}
public class Program
{
static void Main(string[] args)
{
// Call Create Employye
List<Employee> EmployeeList =
Employee.CreateEmployee();
IsEmployeeApplicableDelegate ObjIsEmployeeApplicableDelegate = new
IsEmployeeApplicableDelegate(Employee.IsApplicable);
Employee.FindEmployee(EmployeeList, ObjIsEmployeeApplicableDelegate);
Console.ReadLine();
}
}
}
