使用依赖注入初始化主窗体中的接口

Question

这是我的代码隐藏形式 ExpressionOfNeeds

private readonly IExpressionOfNeeds _expressionOfNeeds;
public FrmExpressionOfNeeds(IExpressionOfNeeds expressionOfNeeds)
{
    InitializeComponent();
    _expressionOfNeeds = expressionOfNeeds;
}
private async void FrmExpressionOfNeeds_Load(object sender, EventArgs e)
{
    GCData.DataSource = await _expressionOfNeeds.GetAllExpressionOfNeeds();
}

这是我 MainForm

背后的代码

private readonly IExpressionOfNeeds _expressionOfNeeds;
private readonly IService2 _service2;
private readonly IService3 _service3;
//and so on and so forth
public XtraMain()
{
    InitializeComponent();
}
private void bbtnExpressionOfNeeds_ItemClick(object sender, ItemClickEventArgs e)
{
    FrmExpressionOfNeeds frme = new(_expressionOfNeeds)
    {
        Name = "FrmExpressionOfNeeds"

    };
    ViewChildForm(frme);
}
private void bbtnForm2_ItemClick(object sender, ItemClickEventArgs e)
{
    Form2 frme = new(_service2)
    {
        Name = "Form2"

    };
    ViewChildForm(frme);
}
private void bbtnForm3_ItemClick(object sender, ItemClickEventArgs e)
{
    Form3 frme = new(_service3)
    {
        Name = "Form3"

    };
    ViewChildForm(frme);
}

等等等等
这是我 Program class

背后的代码

static void Main()
{
    var builder = new HostBuilder()
                 .ConfigureServices((hostContext, services) =>
                 {
                     services.AddScoped<XtraMain>();
                     services.AddSingleton<ISqlDataAccess, SqlDataAccess>();
                     services.AddSingleton<IExpressionOfNeeds, ExpressionOfNeeds>();
                 });
    var host = builder.Build();
    using (var serviceScope = host.Services.CreateScope())
    {
        var services = serviceScope.ServiceProvider;
        var mainform = services.GetRequiredService<XtraMain>();
        Application.Run(mainform);
    }
}

问题是 _expressionOfNeeds 的值始终为空，我找不到初始化它的方法
更新
我有很多表单和很多接口
我仅将其限制为一个示例，因此代码不会太大。

Answer 1

我建议创建一个工厂来获取主表单所需的表单

public interface IFormFactory {
    TForm Create<TForm>() where TForm : Form;
}

假设在这种情况下要创建的类型都派生自 Form

实施将使用服务提供商来解析提供的表单类型

public class FormFactory: IFormFactory {
    private readonly IServiceProvider services;

    public FormFactory(IServiceProvider services) {
        this.services = services;
    }

    public TForm Create<TForm>() where TForm : Form {
        return services.GetRequiredService<TForm>();
    }
}

主窗体将需要依赖于工厂，以便它可以根据需要创建窗体

//...

private readonly IFormFactory factory;

public XtraMain(IFormFactory factory) {
    InitializeComponent();
    this.factory = factory;
}
private void bbtnExpressionOfNeeds_ItemClick(object sender, ItemClickEventArgs e) {
    FrmExpressionOfNeeds frme = factory.Create<FrmExpressionOfNeeds>();
    frme.Name = "FrmExpressionOfNeeds";
    ViewChildForm(frme);
}
private void bbtnForm2_ItemClick(object sender, ItemClickEventArgs e) {
    Form2 frme = factory.Create<Form2>();
    frme.Name = "Form2";
    ViewChildForm(frme);
}
private void bbtnForm3_ItemClick(object sender, ItemClickEventArgs e) {
    Form3 frme = factory.Create<Form3>();
    frme.Name = "Form3";
    ViewChildForm(frme);
}

//...

确保服务提供商解决的所有问题都在启动时注册

static void Main() {
    var builder = new HostBuilder()
                 .ConfigureServices((hostContext, services) => {
                    services.AddScoped<XtraMain>();
                    services.AddTransient<FrmExpressionOfNeeds>();
                    services.AddTransient<Form2>();
                    services.AddTransient<Form3>();
                    services.AddSingleton<ISqlDataAccess, SqlDataAccess>();
                    services.AddSingleton<IExpressionOfNeeds, ExpressionOfNeeds>();
                    services.AddSingleton<IFormFactory, FormFactory>();
                 });
    var host = builder.Build();
    using (var serviceScope = host.Services.CreateScope()) {
        IServiceProvider services = serviceScope.ServiceProvider;
        XtraMain mainform = services.GetRequiredService<XtraMain>();
        Application.Run(mainform);
    }
}

这样，无论有多少表单和接口，所有依赖项都可以由容器解析和注入。

Answer 2

你快到了。您已将表单和服务注册到 DI 容器中，但忘记将接口注入到表单的构造函数中。

您必须将依赖接口添加到表单的构造函数（首选解决方案），或者稍后在需要时从服务提供商处获取它们的实例。

您可以在下面找到分步示例 post:

How to use dependency injection in WinForms.

假设你有一个 MainForm 依赖于 IMyServie，那么你应该有一个像这样的构造函数：

IMyService _myService;
public MainForm(IMyService myService)
{
    _myService = myService;
}

然后，一旦您将 MainForm 和 IMyService 注册到 DI 容器并从服务提供商处获取实例，一切都会按预期进行。这是主要入口点：

static class Program
{
    public static IServiceProvider ServiceProvider { get; private set; }

    [STAThread]
    static void Main()
    {
        ApplicationConfiguration.Initialize();
        var host = CreateHostBuilder().Build();
        ServiceProvider = host.Services;
        Application.Run(ServiceProvider.GetRequiredService<MainForm>());
    }

    static IHostBuilder CreateHostBuilder()
    {
        return Host.CreateDefaultBuilder()
            .ConfigureServices((context, services)=>{
                services.AddTransient<IMyService, MyService>();
                services.AddTransient<MainForm>();
            });
    }
}

如果出于某种原因（就像我在链接答案中解释的那样）您需要获取服务实例而不将其注入构造函数，那么您可以使用 Program.ServiceProvider.GetRequiredService<SomeFormOrService>().

使用依赖注入初始化主窗体中的接口

Initialize interfaces in main form with dependency injection

c#

dependency-injection

winforms

.net-6.0