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How to Use ViewModel in Asp.Net MVC

ViewModel is used to specify the fields which may be required in create, edit or list the data on a strongly typed view. Asp.Net MVC uses these type of classes in which each field may contains specific validation rules using data annotations. These validation rules may be used for any type of data like DateTime, String or Integer.

Basically, Models are used to create database in Entity Framework and may be used to access database using the same name of classes. To differentiate the model with views programmer have to use ViewModel to interact view to make them strongly typed.

According to our previous article, Student Model have a list of field i.e. Id (primary key), name, age and city. In a view, we want to show only name and city then we have to create a view model with only these two fields and some validation rules like written below:

public class StudentViewModel
{
[Display(Name="Student Name")]
[Required(ErrorMessage="Name Required")]
public string Name { get; set; }

[Display(Name = "Student City")]
[Required(ErrorMessage = "City Required")]
public string City { get; set; }
}
Open our controller and write an action type of HttpGet with some line of code to return just a blank view model of type StudentViewModel.
public ActionResult StudentVM()
{
StudentViewModel svm = new StudentViewModel();
return View(svm);
}
Add a strongly typed view to select particular options listed in the below image:

How to Use ViewModel in Asp.Net MVC

The view page which is automatically creates as strongly typed, when run in the browser, have the display name for each field set in the ViewModel. When create button is clicked without any value, both of them show the error messages assigned previously in the ViewModel.

How to Use ViewModel in Asp.Net MVC

So ViewModels are used to organize and manage data in strongly typed view with more flexible way than other complex ways like Models or ViewBag etc.

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