View Models in MVC

Introduction

In the MVC (Model-View-Controller) architecture, particularly in web development with technologies like ASP.NET, the concept of a view model is both pivotal and powerful. It acts as a bridge between the model (data) and the view (user interface).

This blog post aims to elucidate what view models are, their benefits in web application development, and how they are used with an example of a customer model in a Razor view.

What is a View Model?

It is a design pattern predominantly used in the MVC and MVVM (Model-View-ViewModel) architectures.

It’s a custom-tailored object designed to supply the view with precisely the data it needs.

Unlike models, which represent the domain data (the data your application is concerned with), view models are specifically crafted for the view layer.

Core Responsibilities

• Data Presentation: Adapts data from the model to formats suitable for the view.
  
• UI Logic: Manages presentation-specific logic like conditional formatting, but not business logic.
  
• Decoupling: Separates the view from direct dependencies on the model, fostering a more modular architecture.

Example: Customer Model in a Razor View

Consider a basic model of a customer:

The Model

public class Customer
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public DateTime DateOfBirth { get; set; }
    public string Address { get; set; }
    public string Postcode { get; set; }
}

The Customer specific ViewModel

To display this data in a view, we use one that combines the first and last names and calculates age:

public class CustomerViewModel
{
    public string FullName { get; set; }
    public int Age { get; set; }
    public string Address { get; set; }
    public string Postcode { get; set; }

    public CustomerViewModel(Customer customer)
    {
        FullName = $"{customer.FirstName} {customer.LastName}";
        Age = DateTime.Today.Year - customer.DateOfBirth.Year;
        Address = customer.Address;
        Postcode = customer.Postcode;
    }
}

In a Razor View

@model CustomerViewModel

<h2>Customer Details</h2>

<p><strong>Name:</strong> @Model.FullName</p>
<p><strong>Age:</strong> @Model.Age</p>
<p><strong>Address:</strong> @Model.Address, @Model.Postcode</p>

Benefits of Using View Models

1. Enhanced Separation of Concerns: They create a clear distinction between the UI logic and business logic, contributing to a cleaner, more maintainable codebase.
   
2. Reduced Complexity in Views: By handling data formatting and preparation in them, the view’s responsibility is limited to displaying data, making it simpler and less prone to bugs.
   
3. Increased Reusability: They can be reused across different views, especially when similar data presentation is needed, enhancing code reusability and reducing redundancy.
   
4. Improved Testability: With business logic separated from presentation logic, they can be unit tested independently from the views, making testing more straightforward and reliable.
   
5. Flexibility in Data Representation: They allow for the customisation of data presentation without altering the underlying business model, granting flexibility in how data is displayed and managed on the UI.
   
6. Easier Refactoring and Maintenance: Changes in the business model don’t necessarily require changes in them or vice versa, making the application easier to refactor and maintain.
   
7. Better Performance Optimisation: They can be optimised for performance in the view layer, such as loading only the necessary data, which can lead to faster page rendering and improved user experience.
   
8. Adaptability to Changing UI Requirements: As user interface requirements evolve, they can be adjusted or extended without impacting the underlying business logic, making it easier to adapt to new requirements.

Conclusion

View models are a crucial aspect of building an extensible and efficient web applications using MVC architecture. They not only streamline the development process by ensuring a clean separation of concerns but also provide a flexible and maintainable approach to handling data and UI logic.

By effectively utilising them, developers can create more scalable, testable, and adaptable web applications.

There is some great documentation here: – https://learn.microsoft.com/en-us/aspnet/mvc/overview/older-versions/mvc-music-store/mvc-music-store-part-3

I have written some related posts here: – What are C# Records, Exploring Playwright’s Trace Viewer

Related posts:

Integrating C# with GraphQL: A Guide for Developers Unit Testing in C# with NUnit The Null Object Pattern NUnit’s Assert.That