如何在我的扩展方法中获取正确的 IServiceProvider 实例

Question

我正在为要在主机构建器中使用的 api 编写扩展方法，并且我需要在其中获取 IServiceProvider 的实例。

我看到了

builder.Services.AddDbContext<T>()

有一个参数

（IServiceProvider，DbContextOptionsBuilder）

，所以我想将其添加到我的扩展方法中，但是如何？

假设我有这个扩展方法：

public static class MyExtensions
{
    public static IServiceCollection AddMyServices(this IServiceCollection services, Action<IServiceProvider, MyServicesOptionBuilder> overrides)
    {
        ...
        return services;
    }
}

预期的用法是这样的：

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddMyServices((serviceProvider, config)=>
{
    var serviceconfiguration = serviceProvider.GetRequiredService<SomeServiceConfiguration>();
    cfg.ConfigureService1(serviceconfiguration);
    cfg.ConfigureService2(serviceconfiguration);

    ....
});

我不明白的是，IServiceProvider 是谁或者如何传入到 Action 参数中的？

Answer 1

这是我创建的示例：

public static class MyExtensions
{
    public static void AddMyServices(this IServiceCollection services, Action<IServiceProvider, MyServicesOptionBuilder> overrides)
    {
        // get IServiceProvider from IServiceCollection
        IServiceProvider serviceProvider = services.BuildServiceProvider();

        // create MyServicesOptionBuilder instance
        var options = new MyServicesOptionBuilder();

        // Let the client set option's value
        overrides.Invoke(serviceProvider, options);

        // create MyDependency instance using the option value that was set by the client
        var dependency = new MyDependency(options.DependencyName);

        services.AddKeyedSingleton("Second", dependency);

        serviceProvider.GetKeyedServices<MyDependency>("Second");

        Debug.Assert(dependency.DependencyName == "This is a different dependency");
        Console.WriteLine(dependency.DependencyName);
    }
}

程序.cs：

// Add services to the container.
builder.Services.AddKeyedSingleton("First" ,new MyDependency("This is a dependency"));

builder.Services.AddMyServices((services, options) =>
{
    var firstDependency = services.GetRequiredKeyedService<MyDependency>("First");

    Debug.Assert(firstDependency.DependencyName == "This is a dependency");
    Console.WriteLine(firstDependency.DependencyName);

    options.DependencyName = "This is a different dependency";
});

我不明白的是，IServiceProvider 是谁或者如何传入到 Action 参数中的？

如您所见，您是创造

IServiceProvider

的人。