Understanding MVC Model

In this post we're going to see what the MVC Model is ? The MVC Model is your program representation of real world objects, processes that make up the subject, purpose or the domain of your application
The MVC Model is a class that handles your business logic, Validation logic or database access logic.
Creting Data Model Can be done in many ways: there is the basic way by creating a class that handle the data access logic. And the other way is to use the Entity Framework
Before we begin we will use a simple data base that handles customer orders. The database has the following structure:



you can download the database definition from this link
Now our first task is to create a data entry page for Inserting the products in the database. so we'll desing a Model Class to handle this operation so here are the steps:

1. Create a New Proeject
2. Add a new class file named Products.cs in the Models folder.
3. Add the following Automatic properties
   

   public string Name {get; set; }
   public string Description { get; set; }

   
   
4. Add a new view named Products.aspx under Views/Products/Products.aspx and add a new controller called ProductsController.cs as this :
   
5. Now in Products.aspx add the following controls:
   
   
   
   

   <%using (Html.BeginForm())
         { %>
         <p>Product Name:<%=Html.TextBox("txtName") %></p>
         <p>Product Description <%=Html.TextBox("txtDesc") %></p>
         <p><input type="submit" value="Add" /></p>
       <% } %>

   
   
6. Now try writing some text in the text boxes and press the button, you'll see that the page posts back and the text disappears as if the form is redrawn. Now that's gonna be a problem cause this means that the data entered won't be passed to the model to insert new record in the database. So what we gonna do for this ?
7. This happened cause the form posted to [URL]/Products which calls
   
   

   public ActionResult Index()
           {
               return View("Products");
           }

   that returns the view and renders the page.
8. Now we want to receive the data from the form. So we’re going to slice the Products.aspx to two methods:
   
   One to respond to the HTTP GET request which will be responsible for rendering the initial blank form when a user requests the form
   
   One to respond to the HTTP POST requests. By default any form rendered by HTML.BeginForm() are submitted by POST method. This action will be responsible for receiving the data from the form.
9. The first function will be like this just returns the blank view:
   
   

   [AcceptVerbs(HttpVerbs.Get)]
           public ActionResult Index()
           {
               return View("Products");
           }
   

   
   
10. The second function will belike this: the attribute
    

    [AcceptVerbs (HttpVerbs.Post)]

    controller that this function will handle the HTTP POST method
    

    [AcceptVerbs (HttpVerbs.Post)]
            public ActionResult GetData()
            {
                
            }
    

    
    
11. Back to our Product Model.cs, add a function that inserts the data of a new product in the database:
    

    static public void InsertProduct(Product NewProduct)
            {
    
                string conString = ConfigurationManager.ConnectionStrings   ["CustomersOrdersDB"].ConnectionString;
                SqlConnection conn = new SqlConnection(conString);
                conn.Open();
                string insertCommand = "insert into products (name,[desc]) values('"+NewProduct.Name+"','"+NewProduct.Description+"')";
                SqlDataAdapter daProducts = new SqlDataAdapter();
                daProducts.InsertCommand = new SqlCommand(insertCommand, conn);
                daProducts.InsertCommand.CommandText = insertCommand;
                daProducts.InsertCommand.CommandType = CommandType.Text;
                daProducts.InsertCommand.ExecuteNonQuery();
                conn.Close();
            }

    
    
12. Now in
    

    Products.aspx

    in the
    

    BeginForm()

    function modify it to be
    

    Html.BeginForm("GetData","Products")

    The BeginForm function has two parameters: ActionName which is the name of the action that will be executed when the form is submitted (GetData function in our case).
    The second parameter is the Controller Name that handles requests from this view which is the
    

    Products

    Controller
    Note:The name of the controller (Products) must be provided without the Controller suffix despite that the controller class is named ProductsController
13. Now in
    

    ProductsController

    our second function GetData() write the following code:
    

    Product NewProduct = new Product();
                NewProduct.Name = Request["txtName"].ToString();
                NewProduct.Description = Request["txtDesc"].ToString();
                Product.InsertProduct(NewProduct);
                return View("Products");
    

    this function receives the values from the text boxes, creates a new
    

    Product

    object and inserts it in the data base
14. Run the form and insert a new product, you’ll see that the record has been inserted in the database.
15. You will notice that after inserting pressing the submit button the page is refreshed with blank field (Responding to HTTP GET method).
16. Now we want to redirect the user to another page after inserting a new record so add a new view to Views/Products folder call it thanks.aspx and replace the last line in the GetData() function with this
    

    return View("Thanks");

    
    
17. So after the user adds a new product he/she will be redirected to Thanks.aspx
    
    

Summary
In this post we introduced the MVC Model in its simplest form. The MVC Model represent the real world object of you application

The MVC model in this application handled the data access operations and thus achieving the separation between the interface and the data access layer which is one of the goals of the MVC pattern.

Download the project from here