c# - Netcore - 将配置应用于框架类

Question

我有一组库，我想将其从 PCL 转移到 netcore。通过此举，我想简化 DI 系统并更新一些内部工作方式。

我想添加的其中一件事是内部对象的配置，就像在 Asp.Net Core 中一样(即 services.AddMvc(opt => {/* Options Stuff*/}); ).我当前的服务集合扩展如下所示:

public static IServiceCollection AddCore(this IServiceCollectionserviceCollection, Action<HttpClientOptions> options)
{
    serviceCollection.AddSingleton<HttpClient>();
    serviceCollection.Configure(options);
    return serviceCollection;
}

配置类如下所示:

public sealed class HttpClientOptions
{
    public HttpMessageHandler MessageHandler { get; set; }

    // Remaining properties omitted for brevity
}

但是我在问自己，如何将配置应用到 HttpClient，因为它是一个框架类，我无法修改它以通过构造函数注入(inject)来获取选项。

有没有办法设置它，还是我必须重新考虑我的配置方法？

Answer 1

serviceCollection.AddSingleton()有一个需要 Func<IServiceProvider, HttpClient> 的重载工厂。

因此，您可以按照以下方式做一些事情:

serviceCollection
    .AddSingleton<HttpClient>((serviceCollectionInstance) => {
        var myOptions = serviceCollectionInstance.GetRequiredService<MyHttpClientOptions>();
        return new HttpClient(myOptions);
    });

甚至

serviceCollection.AddSingleton<MyHttpClientFactory>(); // <-- your very own factory class that creates arbitrarily complex options
serviceCollection.AddSingleton<HttpClient>(_ => _.GetRequiredService<MyHttpClientFactory>().CreateHttpClient());

如果你真的想过火，你甚至可以编写自己的扩展方法来实现流畅的配置风格:

public static class ServiceCollectionExtensions
{
    public static void AddHttpClient(this IServiceCollection @this, Action<HttpClientOptions> configure = null)
    {
        var options = new HttpClientOptions();

        if (configure != null)
        {
            configure(options);
        }

        @this.AddSingleton<HttpClient>(options);
    }
}

用法:

serviceCollection.AddHttpClient(opts => {
    opts.HttpMessageHandler = // etc
});