Explain the Front Controller pattern with an example in C#

The Front Controller is a design pattern that provides a centralized entry point for handling requests in a web application. The Front Controller pattern consists of a single controller class that receives all requests and dispatches them to the appropriate handler.

The Front Controller acts as a central point of control for handling requests in a web application. It can handle different types of requests and route them to the appropriate handler. The Front Controller encapsulates the logic for handling requests, allowing you to modify the behavior of the application without changing the request handling code.

In C#, these are the steps to implement the Front Controller pattern:

1. Create a Front Controller class: This class will be responsible for receiving all requests and dispatching them to the appropriate handler. It should contain a method to handle each type of request, and a method to dispatch the request to the appropriate handler.
   public class FrontController
{
private Dictionary<string, IController> _controllers = new Dictionary<string, IController>();
public FrontController()
{
_controllers.Add("home", new HomeController());
_controllers.Add("about", new AboutController());
}
public void DispatchRequest(string request)
{
// Get the appropriate controller based on the request
IController controller = GetController(request);
// Call the appropriate method on the controller
controller.HandleRequest(request);
}
private IController GetController(string request)
{
if (!_controllers.ContainsKey(request))
{
throw new Exception("Controller not found.");
}
return _controllers[request];
}
}
2. Create handler interface: This interface defines the method that the Front Controller will call to handle the request.
   public interface IHandler
   {
void HandleRequest();
}
3. Create concrete handlers: Implement the IHandler interface for each type of request you want to handle.
   public class HomeHandler : IHandler
{
public void HandleRequest()
{
Console.WriteLine("Displaying home page.");
}
}
public class AboutHandler : IHandler
{
public void HandleRequest()
{
Console.WriteLine("Displaying about page.");
}
}
4. Register handlers with the Front Controller: In the main program start-up, create instances of the concrete handlers and register them with the Front Controller.
   FrontController controller = new FrontController();
controller.RegisterHandler("home", new HomeHandler());
controller.RegisterHandler("about", new AboutHandler());
5. Call the Front Controller: In the program, call the Front Controller’s DispatchRequest method with the appropriate request type.
   controller.DispatchRequest("home");
controller.DispatchRequest("about");Output will be:
   Displaying home page.
   Displaying about page.

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