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ViewModels - (ASP.NET MVC Models)

In ASP.NET MVC, a ViewModel is a class that contains data and behavior required by a specific view. ViewModels are commonly used to separate concerns between the view and its underlying model, and to enable better testability and maintainability of your application. In this tutorial, we'll discuss what ViewModels are and how to use them in ASP.NET MVC.

Syntax

The syntax for creating a ViewModel in ASP.NET MVC is to create a class that represents the data and behavior required by a specific view. For example:

public class OrderViewModel
{
    public int OrderId { get; set; }
    public string CustomerName { get; set; }
    public decimal TotalAmount { get; set; }
    public DateTime OrderDate { get; set; }
}

Example

Let's say we have an ASP.NET MVC application that displays a list of orders and their details. We could create a OrderViewModel class to represent the data required by the view as follows:

public class OrderViewModel
{
    public int OrderId { get; set; }
    public string CustomerName { get; set; }
    public decimal TotalAmount { get; set; }
    public DateTime OrderDate { get; set; }
}

public class OrdersController : Controller
{
    private readonly ApplicationDbContext _context;

    public OrdersController(ApplicationDbContext context)
    {
        _context = context;
    }

    public ActionResult Index()
    {
        var orders = _context.Orders.ToList();
        var orderViewModels = orders.Select(o => new OrderViewModel
        {
            OrderId = o.OrderId,
            CustomerName = o.CustomerName,
            TotalAmount = o.Items.Sum(i => i.Price),
            OrderDate = o.OrderDate
        }).ToList();

        return View(orderViewModels);
    }
}

In this example, we have a separate OrderViewModel class that represents the data required by the view. The OrdersController retrieves the orders from the database and maps them to a list of OrderViewModels using LINQ's Select method.

Explanation

ViewModels in ASP.NET MVC help to separate concerns between the view and its underlying model. Instead of exposing the entire model to the view, a ViewModel contains only the specific data and behavior required by the view. This can help to improve testability and maintainability of your application.

A ViewModel can be used to represent any data that needs to be displayed in a view, including data that is calculated or aggregated from the underlying model.

Use

ViewModels in ASP.NET MVC are used to represent data and behavior required by a specific view. They can be used to:

  • Provide the view with a specific subset of data from the underlying model
  • Transform or aggregate data from the underlying model into a format suitable for display in the view
  • Provide additional behavior that is specific to the view, such as formatting or validation

Important Points

Here are some important points to keep in mind when working with ViewModels in ASP.NET MVC:

  • ViewModels should contain only the data and behavior required by the view they are associated with
  • ViewModels can help to improve testability and maintainability of your application
  • ViewModels can be used to transform or aggregate data from the underlying model into a format suitable for display in the view

Summary

In this tutorial, we discussed ViewModels in ASP.NET MVC, which are used to represent data and behavior required by a specific view. We covered the syntax, example, explanation, use, and important points of ViewModels in ASP.NET MVC. With this knowledge, you can use ViewModels to improve testability and maintainability of your ASP.NET MVC application.

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