Creating the Controllers

This article is relevant to entity models that utilize the deprecated Visual Studio integration of Telerik Data Access. The current documentation of the Data Access framework is available here.

The "C" in MVC stands for controller. The controller gathers up data and sends it to a view and responds to requests from the view. In this topic, you will implement the second part of the MVC pattern, i.e. the controllers.

To Create the Controllers:

In the CarRentWebSite project, right-click the Controllers folder, point Add and select Controller....
The Add Controller dialog appears. From the Template drop-down, select Controller with empty read/write actions.
Add two controllers named respectively CarController and CategoryController.
Each controller class will be created with ActionResult methods: Index, Details, Create, Edit and Delete.
Open the CategoryController class. Add the following using/Imports statements:
```
using CarRentWebSite.OpenAccess
```
```
Imports CarRentWebSite.OpenAccess
```

You need to define an EntitiesModel field in the CategoryController. The context will be initialized in the Initialize method:

private EntitiesModel dbContext;

protected override void Initialize( System.Web.Routing.RequestContext requestContext )
{
   base.Initialize( requestContext );
   this.dbContext = ContextFactory.GetContextPerRequest();
}

Private dbContext As EntitiesModel

Protected Overrides Sub Initialize(ByVal requestContext As System.Web.Routing.RequestContext)
    MyBase.Initialize(requestContext)
    Me.dbContext = ContextFactory.GetContextPerRequest()
End Sub

The job of the Index method will be to return a list of Categories to be displayed in a view. By default an empty view is displayed.

public ActionResult Index()
{
   return View( this.dbContext.Categories.ToList() );
}

Function Index() As ActionResult
 Return View(Me.dbContext.Categories.ToList())
End Function

The purpose of the Details method will be to return information for the current Category.

public ActionResult Details(int id)
{
   return View( this.dbContext.Categories.FirstOrDefault( category => category.CategoryID == id ) );
}

Function Details(ByVal id As Integer) As ActionResult
 Return View(Me.dbContext.Categories.FirstOrDefault(Function(category) category.CategoryID = id))
End Function

The next step is to add controller logic for creating new categories. The first Create method returns an empty View. You don't need to modify it (for now). The second Create method is the one that will be called when the view posts back. By default, the template told the second Create method to expect a FormCollection as a parameter. Because the Create view will be created as a strongly-typed view, it will be able to pass back a strongly typed Category object. Change the declaration of the second Create method to accept a Category object instead of a FormCollection. Next, modify the Create method so that it saves the new Category object to the database. In that method you are taking the new Category object and pass it to the OpenAccessContext. Then, the SaveChanges method is called.
```
public ActionResult Create()
{
   return View();
}

[HttpPost]
public ActionResult Create( Category newCategory )
{
   try
   {
       this.dbContext.Add( newCategory );
       this.dbContext.SaveChanges();
       return RedirectToAction( "Index" );
   }
   catch
   {
       return View();
   }
}
```
```
Function Create() As ActionResult
 Return View()
End Function

<HttpPost()> _
Function Create(ByVal newCategory As Category) As ActionResult
 Try
  Me.dbContext.Add(newCategory)
  Me.dbContext.SaveChanges()
  Return RedirectToAction("Index")
 Catch
  Return View()
 End Try
End Function
```

The next method you are going to implement is the Edit method. When the user edits a category, you will first need to retrieve that category from the database and then send it to the Edit view. By default, the template told the second Edit method to expect a FormCollection as a parameter. However, the Edit view will be created as a strongly-typed view. That's why it will be able to pass back a strongly typed Category object. Change the declaration of the second Edit method to accept a Category object instead of a FormCollection The purpose of the "postback" Edit method is to update the Category in the database with the new data that came from the view. The logic is pretty simple. You need to load the original Category object from the database and modify it with the new values. After that, you need to call the SaveChanges method.

public ActionResult Edit( int id )
{
   return View( this.dbContext.Categories.FirstOrDefault( category => category.CategoryID == id ) );
}

[HttpPost]
public ActionResult Edit( int id, Category categoryToUpdate )
{
   try
   {
       // 1. Load the original category from the database.
       Category originalCategory =
           this.dbContext.Categories.FirstOrDefault( category => category.CategoryID == id );

       // 2. Update with the new data.
       originalCategory.CategoryName = categoryToUpdate.CategoryName;
       originalCategory.ImageFileName = categoryToUpdate.ImageFileName;

       // 3. Save changes.
       this.dbContext.SaveChanges();

       return RedirectToAction( "Index" );
   }
   catch
   {
       return View();
   }
}

Function Edit(ByVal id As Integer) As ActionResult
 Return View(Me.dbContext.Categories.FirstOrDefault(Function(category) category.CategoryID = id))
End Function

<HttpPost()> _
Function Edit(ByVal id As Integer, ByVal categoryToUpdate As Category) As ActionResult
 Try
  ' 1. Load the original category from the database.
  Dim originalCategory As Category =
   Me.dbContext.Categories.FirstOrDefault(Function(category) category.CategoryID = id)

  ' 2. Update with the new data.
  originalCategory.CategoryName = categoryToUpdate.CategoryName
  originalCategory.ImageFileName = categoryToUpdate.ImageFileName

  ' 3. Save changes.
  Me.dbContext.SaveChanges()

  Return RedirectToAction("Index")
 Catch
  Return View()
 End Try
End Function

Deleting a Category will work analogically. The first Delete method is absolutely the same as the corresponding Edit method. And the postback Delete method is similar. First, you need to retrieve the original category from the database and then delete it.

public ActionResult Delete( int id )
{
   return View( this.dbContext.Categories.FirstOrDefault( category => category.CategoryID == id ) );
}

[HttpPost]
public ActionResult Delete( int id, FormCollection collection )
{
   try
   {
       // 1. Load original category from the database.
       Category categoryToDelete =
           this.dbContext.Categories.FirstOrDefault( category => category.CategoryID == id );

       // 2. Pass it to the Delete method.
       this.dbContext.Delete( categoryToDelete );

       // 3. Save changes.
       this.dbContext.SaveChanges();

       return RedirectToAction( "Index" );
   }
   catch
   {
       return View();
   }
}

Function Delete(ByVal id As Integer) As ActionResult
 Return View(Me.dbContext.Categories.FirstOrDefault(Function(category) category.CategoryID = id))
End Function

<HttpPost()> _
Function Delete(ByVal id As Integer, ByVal collection As FormCollection) As ActionResult
 Try
  ' 1. Load original category from the database.
  Dim categoryToDelete As Category =
   Me.dbContext.Categories.FirstOrDefault(Function(category) category.CategoryID = id)

  ' 2. Pass it to the Delete method.
  Me.dbContext.Delete(categoryToDelete)

  ' 3. Save changes.
  Me.dbContext.SaveChanges()

  Return RedirectToAction("Index")
 Catch
  Return View()
 End Try
End Function

The implementation of the CarController is absolutely the same. The code for the CarController is listed below.

using System.Linq;
using System.Web.Mvc;
using CarRentWebSite.OpenAccess;

namespace CarRentWebSite.Controllers
{
   public class CarController : Controller
   {
       private EntitiesModel dbContext;

       protected override void Initialize( System.Web.Routing.RequestContext requestContext )
       {
           base.Initialize( requestContext );

           this.dbContext = ContextFactory.GetContextPerRequest();
       }

       public ActionResult Index()
       {
           return View( this.dbContext.Cars.ToList() );
       }

       public ActionResult Details( int id )
       {
           return View( dbContext.Cars.FirstOrDefault( c => c.CarID == id ) );
       }

       public ActionResult Create()
       {
           return View();
       }

       [HttpPost]
       public ActionResult Create( Car newCar )
       {
           try
           {
               this.dbContext.Add( newCar );
               this.dbContext.SaveChanges();

               return RedirectToAction( "Index" );
           }
           catch
           {
               return View();
           }
       }

       public ActionResult Edit( int id )
       {
           return View( this.dbContext.Cars.FirstOrDefault( c => c.CarID == id ) );
       }

       [HttpPost]
       public ActionResult Edit( int id, Car carToUpdate )
       {
           try
           {
               Car originalCar = dbContext.Cars.FirstOrDefault( c => c.CarID == id );
               originalCar.ABS = carToUpdate.ABS;
               originalCar.AirConditioner = carToUpdate.AirConditioner;
               originalCar.ASR = carToUpdate.ASR;
               originalCar.Available = carToUpdate.Available;
               originalCar.CarYear = carToUpdate.CarYear;
               originalCar.DVDPlayer = carToUpdate.DVDPlayer;
               originalCar.Latitude = carToUpdate.Latitude;
               originalCar.Longitude = carToUpdate.Longitude;
               originalCar.ImageFileName = carToUpdate.ImageFileName;
               originalCar.Make = carToUpdate.Make;
               originalCar.Model = carToUpdate.Model;
               originalCar.Mp3Player = carToUpdate.Mp3Player;
               originalCar.Navigation = carToUpdate.Navigation;
               originalCar.NumberOfRatings = carToUpdate.NumberOfRatings;
               originalCar.Rating = carToUpdate.Rating;
               originalCar.TagNumber = carToUpdate.TagNumber;

               dbContext.SaveChanges();

               return RedirectToAction( "Index" );
           }
           catch
           {
               return View();
           }
       }

       public ActionResult Delete( int id )
       {
           return View( this.dbContext.Cars.FirstOrDefault( c => c.CarID == id ) );
       }

       [HttpPost]
       public ActionResult Delete( int id, FormCollection collection )
       {
           try
           {
               Car car = this.dbContext.Cars.FirstOrDefault( c => c.CarID == id );
               dbContext.Delete( car );

               dbContext.SaveChanges();

               return RedirectToAction( "Index" );
           }
           catch
           {
               return View();
           }
       }
   }
}

Imports CarRentWebSite.OpenAccess

Public Class CarController
    Inherits System.Web.Mvc.Controller

    Private dbContext As EntitiesModel

    Protected Overrides Sub Initialize(ByVal requestContext As System.Web.Routing.RequestContext)
        MyBase.Initialize(requestContext)

        Me.dbContext = ContextFactory.GetContextPerRequest()
    End Sub

    Function Index() As ActionResult
        Return View(Me.dbContext.Cars.ToList())
    End Function

    Function Details(ByVal id As Integer) As ActionResult
        Return View(Me.dbContext.Cars.FirstOrDefault(Function(car) car.CarID = id))
    End Function

    Function Create() As ActionResult
        Return View()
    End Function

    <HttpPost()> _
    Function Create(ByVal newCar As Car) As ActionResult
        Try
            Me.dbContext.Add(newCar)
            Me.dbContext.SaveChanges()

            Return RedirectToAction("Index")
        Catch
            Return View()
        End Try
    End Function

    Function Edit(ByVal id As Integer) As ActionResult
        Return View(Me.dbContext.Cars.FirstOrDefault(Function(car) car.CarID = id))
    End Function

    <HttpPost()> _
    Public Function Edit(ByVal id As Integer, ByVal carToUpdate As Car) As ActionResult
        Try
            Dim originalCar As Car = dbContext.Cars.FirstOrDefault(Function(c) c.CarID = id)

            originalCar.ABS = carToUpdate.ABS
            originalCar.AirConditioner = carToUpdate.AirConditioner
            originalCar.ASR = carToUpdate.ASR
            originalCar.Available = carToUpdate.Available
            originalCar.CarYear = carToUpdate.CarYear
            originalCar.DVDPlayer = carToUpdate.DVDPlayer
            originalCar.Latitude = carToUpdate.Latitude
            originalCar.Longitude = carToUpdate.Longitude
            originalCar.ImageFileName = carToUpdate.ImageFileName
            originalCar.Make = carToUpdate.Make
            originalCar.Model = carToUpdate.Model
            originalCar.Mp3Player = carToUpdate.Mp3Player
            originalCar.Navigation = carToUpdate.Navigation
            originalCar.NumberOfRatings = carToUpdate.NumberOfRatings
            originalCar.Rating = carToUpdate.Rating
            originalCar.TagNumber = carToUpdate.TagNumber

            dbContext.SaveChanges()

            Return RedirectToAction("Index")
        Catch
            Return View()
        End Try
    End Function

    Function Delete(ByVal id As Integer) As ActionResult
        Return View(Me.dbContext.Cars.FirstOrDefault(Function(car) car.CarID = id))
    End Function

    <HttpPost()> _
    Function Delete(ByVal id As Integer, ByVal collection As FormCollection) As ActionResult
        Try
            ' 1. Load original car from the database.
            Dim carToDelete As Car = Me.dbContext.Cars.FirstOrDefault(Function(car) car.CarID = id)

            ' 2. Pass it to the Delete method.
            Me.dbContext.Delete(carToDelete)

            ' 3. Save changes.
            Me.dbContext.SaveChanges()

            Return RedirectToAction("Index")
        Catch
            Return View()
        End Try
    End Function
End Class

In this topic, you implemented the second part of the MVC pattern, i.e. the Controller. The next step is to create the views.