Where did use delegates in your project - Part 1

Where did you use delegates in your project?

or
How did you use delegates in your project?
or
Usage of delegates in a Real Time Project?

This is a very common c sharp interview question. Delegates is one of the very important aspects to understand. Most of the interviewers ask you to explain the usage of delegates in a real time project that you have worked on. 

Delegates are extensively used by framework developers. Let us say we have a class called Employee as shown below.

Employee Class

The Employee class has the following properties.
1. Id
2. Name
3. Experience
4. Salary

Now, I want you to write a method in the Employee class, which can be used to promote employees. The method should take a list of Employee objects as a parameter, and should print the names of all the employees who are eligible for a promotion. But the logic, based on which the employee gets promoted should not be hard coded. At times, we may promote employees based on their experience and at times we may promote them based on their salary or may be some other condition. So, the logic to promote employees should not be hard coded with in the method.

To achieve this, we can make use of delegates. So, now I would design my class as shown below. We also, created a delegate EligibleToPromote. This delegate takes Employee object as a parameter and returns a boolean. In the Employee class, we have PromoteEmpoloyee method. This method takes in a list of Employees and a Delegate of type EligibleToPromote as parameters. The method, then loops thru each employee object, and passes it to the delegate. If the delegate returns true, then them Employee is promoted, else not promoted. So, with in the method we have not hard coded any logic on how we want to promote employees.