ASP.NET 5 MVC 6 DI:ServiceProvider无法解析类型

Question

在下面的代码中,serviceProvider.GetService<DocumentDbConnection>()解析为null:

public void ConfigureService(IServiceCollection services)
{
    var serviceProvider = services.BuildServiceProvider();

    services.AddSingleton<DocumentDbConnection>(
        x => new DocumentDbConnection(uri, authKey));

    // service is null?
    var connection = serviceProvider.GetService<DocumentDbConnection>();

    services.AddTransient<IStopRepository, StopRepository>(
        x => new StopRepository(connection, databaseId, collectionId));
}

为什么会这样？该类型在GetService被调用之前被注册,所以它不能解析为单例吗？

Answer 1

您在注册之前正在构建服务提供商DocumentDbConnection.您应该首先注册您需要的服务.然后BuildServiceProvider将构建一个服务提供商,其服务已注册到那时:

services.AddSingleton<DocumentDbConnection>(x => new DocumentDbConnection(uri, authKey));
var serviceProvider = services.BuildServiceProvider();

// code using serviceProvider