如何在 ASP.NET Core v2 中传递字符串和注入的依赖项

Question

我的 ASP.NET Core v2 项目的 Startup.cs 类中有以下方法。我的问题是如何设置一个类/服务，其中一个字符串值被传递给一个类，以及一个注入的依赖项。

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        // Add custom services.
        services.AddSingleton<IMyAssistantClass, MyAssistantClass);
        services.AddSingleton<MyClassManager>(s => new  MyClassManager("connectionString", /* How to inject IMyAssistantClass? */);

        // Other setup....
    }

Answer 1

public void ConfigureServices(IServiceCollection services)
{
  services.AddSingleton<IMyAssistantClass, MyAssistantClass);
  services.AddSingleton<MyClassManager>(s => 
    {
      var imy = (IMyAssistantClass) s.GetService(typeof(IMyAssistantClass))
      new  MyClassManager("connectionString", imy);
    }
  );
}

// 使它更方便的好方法是添加扩展方法IServiceCollection，例如

public static T Resolve<T>(this IServiceProvider serviceProvider)
{
    return (T) serviceProvider.GetService(typeof(T));
}

然后你可以打电话 s.Resolve<IMyAssistantClass>();

Answer 2

将变量提升connectionString为参数对象并将该对象注册到容器中：

public class MyClassManagerSettings
{
    public readonly string ConnectionString;

    public MyClassManagerSettings(string connectionString) {
        this.ConnectionString = connectionString
            ?? throw new ArgumentNullException(nameof(connectionString));
    }
}

public class MyClassManager
{
    public MyClassManager(
        MyClassManagerSettings settings, IMyAssistantClass assistant)
    {
        ...
    }
}

您可以按如下方式注册：

services.AddSingleton<IMyAssistantClass, MyAssistantClass);
services.AddSingleton<MyClassManager>();
services.AddSingleton(new MyClassManagerSettings("myConnectionString"));