本文记录下WPF程序如何使用依赖注入。代码是在之前WPF使用MVVM模式开发的代码基础上修改的，MVVM的内容见下面链接。
WPF使用MVVM模式开发

废话不多说，直接上代码：

1. nuget添加Microsoft.Extensions.DependencyInjection包
   

2. 修改App.xaml.cs文件如下：

public App()
        {
            Services = ConfigureServices();
            //this.InitializeComponent();
        }

        /// <summary>
        /// Gets the current <see cref="App"/> instance in use
        /// </summary>
        public new static App Current => (App)Application.Current;

        /// <summary>
        /// Gets the <see cref="IServiceProvider"/> instance to resolve application services.
        /// </summary>
        public IServiceProvider Services { get; }

        /// <summary>
        /// Configures the services for the application.
        /// </summary>
        private static IServiceProvider ConfigureServices()
        {
            var services = new ServiceCollection();

            services.AddSingleton<MainView>();

            services.AddSingleton<MainViewModel>();
            services.AddSingleton<ITestService, TestService>();
            

            return services.BuildServiceProvider();
        }

        protected override void OnStartup(StartupEventArgs e)
        {
            Services.GetRequiredService<MainView>()
                .Show();

            base.OnStartup(e);
        }

3. App.xaml文件中把StartupUri去掉，窗口的启动入口上方代码中已经放在了OnStartup方法中。
4. MainView中使用依赖注入viewmodel

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using WpfMVVM.ViewModels;

namespace WpfMVVM.Views
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainView : Window
    {
        protected readonly MainViewModel _VM;
        public MainView(MainViewModel VM)
        {
            InitializeComponent();

            DataContext = _VM = VM;
        }
    }
}

5.代码库