A simple example of using dependency injection using Unity in WPF

Step 1: Create a new Visual Studio project Step 2: Add the necessary Unity reference Select Tools > NuGet Package Manager. Type in the following command: [code language="txt"] Install-Package Unity -Version 4.0.1 [/code] Unity website for NuGet can be found here: https://www.nuget.org/packages/Unity/ Step 3: Remove the startup URL In App.xaml get rid of the StartupUri value: Step 4: Add the Model class / interface IModel.cs [code language="csharp"] namespace DependencyInjection { public interface IModel { } } [/code] Model.cs [code language="csharp"] namespace DependencyInjection { public class Model : IModel { public Model() { Text = "Hello"; } public string Text { get; set; } } } [/code] Step 5: Add the ViewModel class To deal with the error that we receive in the XAML when a ViewModel has "No parameterless constructor defined for this object" - be sure to create a parameterless constructor that will call the standard constructor. MainWindowViewModel.cs [code language="csharp"] namespace DependencyInjection { public class MainWindowViewModel { private Model _model; public MainWindowViewModel() { } public MainWindowViewModel(Model model) { _model = model; } } } [/code] Step 6: Initialise the View Model on application startup Here app.xaml.cs is modified as follows: [code language="csharp"] using System.Windows; using Microsoft.Practices.Unity; namespace DependencyInjection { /// <summary> /// Interaction logic for App.xaml /// </summary> public partial class App : Application { protected override void OnStartup(StartupEventArgs e) { base.OnStartup(e); IUnityContainer container = new UnityContainer(); container.RegisterType<IModel, Model>(); var mainWindowViewModel = container.Resolve<MainWindowViewModel>(); var window = new MainWindow {DataContext = mainWindowViewModel}; window.Show(); } } } [/code] And that is all there is to it. On debugging notice that on startup the ViewModel is dependency injected with the Model:

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