C# 难以使用WebAPI和OWIN实现统一依赖注入

当我尝试在我的应用程序上调用控制器API端点时，出现以下错误：

   {
  "Message": "An error has occurred.",
  "ExceptionMessage": "An error occurred when trying to create a controller of type 'ProviderController'. Make sure that the controller has a parameterless public constructor.",
  "ExceptionType": "System.InvalidOperationException",
  "StackTrace": "   at System.Web.Http.Dispatcher.DefaultHttpControllerActivator.Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)\r\n   at System.Web.Http.Controllers.HttpControllerDescriptor.CreateController(HttpRequestMessage request)\r\n   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()",
  "InnerException": {
    "Message": "An error has occurred.",
    "ExceptionMessage": "Type 'mynamespace.api.controllers.ProviderController' does not have a default constructor",
    "ExceptionType": "System.ArgumentException",
    "StackTrace": "   at System.Linq.Expressions.Expression.New(Type type)\r\n   at System.Web.Http.Dispatcher.DefaultHttpControllerActivator.GetInstanceOrActivator(HttpRequestMessage request, Type controllerType, Func`1& activator)\r\n   at System.Web.Http.Dispatcher.DefaultHttpControllerActivator.Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)"
  }
} 

UnityConfig.cs：

public static class UnityConfig
{
    #region Unity Container

    /// <summary>
    /// Load types in Unity Container 
    /// </summary>
    private static Lazy<IUnityContainer> container = new Lazy<IUnityContainer>(() =>
    {
        var container = new UnityContainer();
        RegisterTypes(container);
        return container;
    });

    /// <summary>
    /// Gets the configured Unity container.
    /// </summary>
    public static IUnityContainer GetConfiguredContainer()
    {
        return container.Value;
    }

    #endregion


    /// <summary>
    /// Register the types into Unity Container.
    /// </summary>
    /// <param name="container"></param>
    public static void RegisterTypes(UnityContainer container)
    {
        container.RegisterType<IProviderService, ProviderService();  
    } 
}

ProviderService.cs：

    public ProviderService()
    {
        this.serviceClient = new ServiceClientAdapter();
    }

---

我花了一上午的时间通读各种各样的文章，但我不知道哪里出了问题。如果我删除Unity并直接在控制器中实例化一个新的ProviderService，一切都会正常工作。

我的问题是一个小疏忽。Startup.cs中对UseWebApi的调用没有将HttpConfiguration配置对象作为参数，而是声明它自己的。这意味着WebAPI和Unity配置了不同的HTTPConfiguration对象，因此WebAPI没有意识到Unity。

答案已经存在！只是为了简单或简短的代码

您可以编写单一方法

    public static void RegisterComponents()
    {
        var container = new UnityContainer();

        // register all your components with the container here
        // it is NOT necessary to register your controllers

        container.RegisterType<IProviderService, ProviderService>();

        GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(container);
    }

---

然后添加UnityConfig.RegisterComponents（）；进入全局文件

我想我可能有类似的问题。我尝试从启动类将配置对象注入DependencyResolver，但没有成功！您是如何解决这个问题的？如果您看看我上面的示例，对于Startup.cs，第一行的config对象用于配置Unity。然后，当调用app.UseWebApi时，将创建一个新的配置对象并将其传递给它。这就是问题所在，应该传入第一行声明的配置。谢谢兄弟！这有帮助。

    public ProviderService()
    {
        this.serviceClient = new ServiceClientAdapter();
    }

    public static void RegisterComponents()
    {
        var container = new UnityContainer();

        // register all your components with the container here
        // it is NOT necessary to register your controllers

        container.RegisterType<IProviderService, ProviderService>();

        GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(container);
    }

    public void Configuration(IAppBuilder app)
    {
        ConfigureOAuth(app);
        HttpConfiguration config = GlobalConfiguration.Configuration;
        app.UseWebApi(config);
    }