确保控制器在网络 api 中具有无参数 public 构造函数？

Question

我正在努力解决使用 untiy 的依赖注入问题。我是按照这个linkhttps://www.asp.net/web-api/overview/advanced/dependency-injection

实现的

但是出现这个错误：

{
  "Message": "An error has occurred.",
  "ExceptionMessage": "An error occurred when trying to create a controller of type 'WebAPIController'. 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 'Fairmoves.Controllers.WebAPIController' does not have a default constructor",
    "ExceptionType": "System.ArgumentException",
    "StackTrace": "   at System.Linq.Expressions.Expression.New(Type type)\r\n   at System.Web.Http.Internal.TypeActivator.Create[TBase](Type instanceType)\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)"
  }
}

我的网站Api控制器：

[RoutePrefix("api/WebAPI")]
public class WebAPIController : ApiController
{
    private readonly IUserBusinessService UserBusinessService;
    private readonly ILoginBusinessService LoginBusinessService;

    //public WebAPIController():base()
    //{
    //}

    public WebAPIController(IUserBusinessService UserBusinessService, ILoginBusinessService LoginBusinessService)
    {
        this.UserBusinessService = UserBusinessService;
        this.LoginBusinessService = LoginBusinessService;
    }
    [HttpPost]
    public IHttpActionResult Login([FromBody]AuthModels.LoginModel model)
    {
        // string strUserId = credentials.LoginName;
        //string strPassword = credentials.Password;
        var serviceResultDAO1 =  LoginBusinessService.LoginUserSubmit(model.LoginName);
    }
}

UnityResolver.cs:

public class UnityResolver:IDependencyResolver
{
    protected IUnityContainer container;

    public UnityResolver(IUnityContainer container)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }
        this.container = container;
    }

    [DebuggerStepThrough]
    public object GetService(Type serviceType)
    {
        try
        {
            return container.Resolve(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return null;
        }
    }

    [DebuggerStepThrough]
    public IEnumerable<object> GetServices(Type serviceType)
    {
        try
        {
            return container.ResolveAll(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return new List<object>();
        }
    }

    public IDependencyScope BeginScope()
    {
        var child = container.CreateChildContainer();
        return new UnityResolver(child);
    }

    public void Dispose()
    {
        container.Dispose();
    }

}

}

WebApiConfig.cs:

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        //config.DependencyResolver = new NinjectResolver();

        var container = new UnityContainer();
        container.RegisterType<ILoginBusinessService, LoginBusinessService>(new HierarchicalLifetimeManager());
        container.RegisterType<IUserBusinessService, UserBusinessService>(new HierarchicalLifetimeManager());
        config.DependencyResolver = new UnityResolver(container);
        //DependencyResolver.SetResolver(new UnityDependencyResolver(container));

        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{action}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
    }
}

无法确定问题出在哪里？请进入代码并让我知道。 我已关注以下所有内容 links

Autofac - Make sure that the controller has a parameterless public constructor

Make sure that the controller has a parameterless public constructor error

但是 none 解决了我的问题。

Answer 1

因为我在一个项目中同时使用 MVC 和 WebAPI，所以我通过使用这个 link 了解到我需要解决这两个依赖关系。

所以，我删除了 WebAPIConfig.cs 文件中的以下代码

var container = new UnityContainer();
    container.RegisterType<ILoginBusinessService, LoginBusinessService>(new HierarchicalLifetimeManager());
    container.RegisterType<IUserBusinessService, UserBusinessService>(new HierarchicalLifetimeManager());
    config.DependencyResolver = new UnityResolver(container);

在我的项目中安装了一个名为 Unity.WebAPI 的包之后。

在 UnityConfig.cs 文件中添加了以下代码

GlobalConfiguration.Configuration.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(container);

就是这样，解决了我的问题！

Answer 2

我猜你正在将 WebAPI 合并到紧密耦合的 MVC 中，现在通过添加一个 Dependency injection 来解耦，因此我正在做与@Edukondalu thaviti 上面所说的相同的事情，除了更改有效的小代码非常适合我。

1. 使用 Manage Nuget Packages

   安装 Unity.WebAPI 和 Unity.WebApi.5.1

   注意：安装完成后会弹出对话框要求覆盖Unity.Config.cs文件，只需selectNo

2. 确保 UnityConfig.RegisterComponents(); 存在于 Application_Start() 方法中 Global.asax.cs 文件

3. 现在包括

   container.RegisterType<IWebAPIBusinessService, WebAPIBusinessService>(); container.RegisterType<IWebAPIDomainService, WebAPIDomainService>(); container.RegisterType<IWebAPIDataService, WebAPIDataService>(); GlobalConfiguration.Configuration.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(container); 在 Unity.Config.cs 文件的方法 RegisterComponents() 中。假设您已经为当前 class.

创建了实例

现在 运行 您的项目。上面的代码对我来说很完美，如果你越过任何错误，请纠正我。