MVVM in .NET

MVVM is a powerful architectural pattern used in .NET desktop applications like WPF, MAUI, and WinUI. In this article, we break down the pattern with a practical example, a diagram, its pros and cons, and step-by-step instructions to build it in Visual Studio Code.

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🧠 What is MVVM?

MVVM is based on three main components:

• Model – Represents data and business logic.
• View – The user interface layer.
• ViewModel – Acts as a mediator between the View and the Model, exposing properties, commands, and state.

Each component has a clear role, helping reduce coupling and making the application easier to maintain and test.

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🔧 Example Implementation in WPF

Let's walk through a simple WPF application using MVVM and CommunityToolkit.Mvvm.

1. The Model

public class User
{
    public string Name { get; set; }
    public int Age { get; set; }
}

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2. The ViewModel

We’ll use [ObservableProperty] and [RelayCommand] from CommunityToolkit.

`using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;

public partial class UserViewModel: ObservableObject
{
[ObservableProperty]
private string name;

[ObservableProperty]
private int age;

[RelayCommand]
private void IncrementAge()
{
    Age++;
}

}`

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3. The View (XAML)

<Window x:Class="MVVMExample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:local="clr-namespace:MVVMExample"
        xmlns:vm="clr-namespace:MVVMExample.ViewModels"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MVVM Example" Height="200" Width="400">

    <Window.DataContext>
        <vm:UserViewModel />
    </Window.DataContext>

    <StackPanel Margin="20">
        <TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}" />
        <TextBlock Text="{Binding Age}" Margin="0,10,0,0"/>
        <Button Content="Increase Age" Command="{Binding IncrementAgeCommand}" />
    </StackPanel>
</Window>

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🧩 MVVM Diagram

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✅ Benefits of MVVM

Benefit	Description
Separation of concerns	UI logic and data are clearly separated.
Testability	ViewModels can be unit tested without the UI.
Scalability	Well-suited for larger apps with many views.
Tooling support	Strong Visual Studio support for bindings and design-time data.

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❌ Drawbacks of MVVM

Drawback	Description
Learning curve	Can be complex for beginners or small projects.
Boilerplate code	Without helpers like CommunityToolkit.Mvvm, code can be verbose.
Overkill for small apps	Not ideal for simple or one-off apps.

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💡 Best Practices for Clean MVVM

• Use CommunityToolkit.Mvvm to reduce boilerplate.
• Keep ViewModels free of direct UI calls (no MessageBox.Show()).
• Use ICommand and bind actions properly.
• Respect the Single Responsibility Principle in your ViewModels.

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🔚 Conclusion

MVVM helps structure your .NET applications in a clean and scalable way. Thanks to tooling like CommunityToolkit.Mvvm, you can simplify much of the boilerplate and focus on writing clear, testable code. Whether you’re building desktop or cross-platform apps, MVVM remains a strong architectural foundation.

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Comments

[Spyros Ponaris]

Hey, thanks for sharing! MVVM is such a powerful pattern — I still remember when Microsoft introduced it. It felt revolutionary at the time, and I was honestly disappointed that Windows Forms never adopted it. Thankfully, CommunityToolkit.Mvvm makes it so much easier now, offering great flexibility and modern tooling. Love working with it!

[Adrián Bailador]

Thanks so much

[Spyros Ponaris]

This week, I’ll be diving into CommunityToolkit.Mvvm and sharing my thoughts on it.

I’ve already written about MVVM and why it still matters in 2025 — even beyond WPF, in platforms like Blazor and WinForms.

Check it out:
🔗 MVVM is not just for WPF — why it still matters in 2025 (even in Blazor and WinForms)

[Spyros Ponaris]

You are welcome..

[Dotallio]

Really love how you emphasized CommunityToolkit.Mvvm to cut down the usual MVVM boilerplate - it's such a game changer once you discover it. The learning curve is real though, did you have any big aha moments that made things finally click for you?