WPF Dependency Injection

App.xaml
App.xaml.cs
MainWindow.xaml
MainWindow.xaml.cs
IDateTimeServices.cs
DateTimeServices.cs
Reference

기본적으로 ASP.NET Core는 클래스와 해당 종속성 간의 IoC(Inversion of Control)를 실현하는 기술인 DI(종속성 주입) 소프트웨어 디자인 패턴을 지원¹한다.

Desktop 애플리케이션 개발에 자주 사용하는 WPF는 개발자가 직접 작성하여 추가하거나 또는 MVVM 패턴을 지원하는 Caliburn.Micro²와 같은 프레임워크를 사용하여 DI(종속성 주입) 환경을 구축한다.

WPF를 이용한 개발에 DI를 적용하는 기본적인 환경 구성을 Microsoft.Extensions.Hosting 패키지를 이용(IHost Interface³)하여 구축할 수 있다.

App.xaml

<Application x:Class="ExamHelloDI.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <!-- StartupUri="MainWindow.xaml" : 기본값 제거-->
    <Application.Resources>
    </Application.Resources>
</Application>

App.xaml.cs

using ExamHelloDI.Services;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System.Windows;

namespace ExamHelloDI
{
    public partial class App
    {
        private readonly IHost _host;

        public App()
        {
            _host = Host.CreateDefaultBuilder().ConfigureServices((context, services) =>
            {
                context.HostingEnvironment.ApplicationName = "ExamHelloDI";
                ConfigureServices(services);
            }).Build();
        }

        private static void ConfigureServices(IServiceCollection services)
        {
            services.AddSingleton<MainWindow>();
            services.AddTransient<IDateTimeServices, DateTimeServices>();
        }

        protected override async void OnStartup(StartupEventArgs e)
        {
            await _host.StartAsync();
            _host.Services.GetRequiredService<MainWindow>().Show();
            base.OnStartup(e);
        }

        protected override async void OnExit(ExitEventArgs e)
        {
            using (_host)
            {
                await _host.StopAsync();
            }
            base.OnExit(e);
        }
    }
}

MainWindow.xaml

<Window x:Class="ExamHelloDI.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d"
        xmlns:local="clr-namespace:ExamHelloDI"
        d:DataContext="{d:DesignInstance local:MainWindow, IsDesignTimeCreatable=True}"
        Title="MainWindow" Height="300" Width="500">

    <Grid>
        <TextBox Grid.Row="0" Text="{Binding DateTime, Mode=OneWay}" />
    </Grid>
</Window>

MainWindow.xaml.cs

using ExamHelloDI.Services;

namespace ExamHelloDI
{
    public partial class MainWindow
    {
        private readonly IDateTimeServices _dateTimeServices;

        public MainWindow(IDateTimeServices dateTimeServices)
        {
            InitializeComponent();

            _dateTimeServices = dateTimeServices;
            DataContext = this;
        }

        public string DateTime => _dateTimeServices.GetDateTimeString();
        // set { } Mode=OneWay
    }
}

IDateTimeServices.cs

namespace ExamHelloDI.Services
{
    public interface IDateTimeServices
    {
        string GetDateTimeString();
    }
}

DateTimeServices.cs

using System;

namespace ExamHelloDI.Services
{
    public class DateTimeServices : IDateTimeServices
    {
        public string GetDateTimeString()
        {
            return DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss");
        }
    }
}

예제에 사용한 소스 코드는 Codewrinkles, “Adding Dependency Injection to WPF applications” 강좌를 참고하여 작성하였다.