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Part 7 - Models in an mvc application

Suggested Videos 
Part 4 - Controllers in an mvc application
Part 5 - Views in an mvc application
Part 6 - ViewData and ViewBag in mvc



In this video we will discuss models in an mvc application.

Let's understand models with an example. We want to retrieve an employee information from tblEmployee table and display it as shown below.




To encapsulate Employee information, add Employee model class to the Models folder. To do this
1. Right click on "Models" folder > Add > Class
2. Name the class as Employee.cs
3. Click "Add"

Copy and paste the following code in Employee.cs class file.
public class Employee
{
    public int EmployeeId { get; set; }
    public string Name { get; set; }
    public string Gender { get; set; }
    public string City { get; set; }
}

Now let's Add EmployeeController class to "Controllers" folder. To do this
1. Right click on "Controllers" folder > Add > Controller
2. Use EmployeeController as the name
3. Click "Add"

We want to use "Employee" model class in EmployeeController. So copy and paste the following "using" statement in "EmployeeController.cs"
using MVCDemo.Models;

By default an Index() Action method is created in EmployeeController. Change the name of the function to Details(). Create an instance of Employee class. For now we will hard code Employee data in this class. In a later video session, we will discuss about retrieving employee information from the database table tblEmployee. At this point EmployeeController should look as shown below.
public ActionResult Details()
{
    Employee employee = new Employee()
    {
        EmployeeId = 101,
        Name = "John",
        Gender = "Male",
        City = "London"
    };
            
    return View();
}

Now, we need to pass the employee model object that we constructed in EmployeeController to a view, so the view can generate the HTML and send it to the requested client. To do this we first need to add a view. To add a view
1. Right click on Details() action method and select "Add View" from the context menu
2. Set
    a)View Name = Details
    b)View Engine = Razor
    c)Select "Create strongly typed view" check box
    d)From the "Model class" dropdownlist, select "Employee (MVCDemo.Models)"
    Note: If Employee class is not visible in the dropdownlist, please build your project and then try adding the view again.
3. Finally click "Add"

At this point, Details.cshtml should be added to "Employee" folder. Please note that "Employee" folder is automatically created and added to "Views" folder.

Copy and paste the following code in Details.cshtml file.
@model MVCDemo.Models.Employee

@{
    ViewBag.Title = "Employee Details";
}

<h2>Employee Details</h2>

<table style="font-family:Arial">
    <tr>
        <td>
            Employee ID:
        </td>
        <td>
            @Model.EmployeeId
        </td>
    </tr>
    <tr>
        <td>
            Name:
        </td>
        <td>
            @Model.Name
        </td>
    </tr>
    <tr>
        <td>
            Gender:
        </td>
        <td>
            @Model.Gender
        </td>
    </tr>
    <tr>
        <td>
            City:
        </td>
        <td>
            @Model.City
        </td>
    </tr>
</table>

At this point if you run the project, and if you navigate to the following URL, you get a runtime error stating - Object reference not set to an instance of an object.
http://localhost/MVCDemo/Employee/Details

To fix this error, pass "Employee" object to the view. The "return" statement in Details() action method need to be modified as shown below.
return View(employee);

That's it. Run the application and navigate to http://localhost/MVCDemo/Employee/Details. We should get the output as expected.

7 comments:

  1. Great videos! I'm receiving an error when trying to view data from my database though that says a primary key has not been defined. However, I do have my Category_ID column set as a primary key in the database. How do I handle this exception. I'm very new to MVC and coding in general so any help is much appreciated!

    ReplyDelete
  2. same problem with me, i think that problem is in Entity, i need solution for this!

    Is your database local or in the SQL Server provider?

    thx

    ReplyDelete
  3. Once UpdateYou are Entity Model

    ReplyDelete
  4. Viewbags/Viewdata should not be used. Bad practice. Stay inside MVC and use the MODEL.

    ReplyDelete
  5. [Table("Employee")]
    public class Employee
    {
    [Key]
    public int EmpId { get; set; }

    [Required]
    public string Name { get; set; }
    public string Gender { get; set; }
    public string City { get; set; }
    }

    ReplyDelete
  6. if you will use view bags or view data . there is higher probability getting error. it is advisable to use Model structure.

    ReplyDelete
  7. Fantastic Videos to make simple a very difficult concept like MVC

    ReplyDelete

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