确保控制器在Web API中具有无参数的公共构造函数? [英] Make sure that the controller has a parameterless public constructor in web api?

问题描述

我正在努力解决使用 uniy 进行依赖项注入的问题.我已根据此链接实现 https://www.asp.net/web-api/overview/advanced/dependency-injection

I am struggling with this problem of dependency injection using untiy. I have implemented according to this link https://www.asp.net/web-api/overview/advanced/dependency-injection

但是出现了这个错误:

{
  "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Web Api控制器:

My Web Api Controller:

[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?能否请您进入代码并让我知道. 我关注了以下所有这些链接

Unable to identify where the problem is? Can please get into the code and let me know. I have followed all these below links

确保控制器具有无参数的public构造函数?

Autofac-确保控制器有一个无参数的公共构造函数

确保控制器有一个使用Ninject的无参数公共构造函数

请确保控制器具有无参数的公共构造函数错误

但是这些都不能解决我的问题.

But none of these solved my problem.

推荐答案

当我在一个项目中同时使用MVC和WebAPI时，通过使用此

As i am using both MVC and WebAPI in one project, i understood by using this link that i need to resolve both dependencies.

因此，我删除了WebAPIConfig.cs文件中的以下代码

So, i removed below code in WebAPIConfig.cs file

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 的软件包之后.

After i installed one package called Unity.WebAPI in my project.

在UnityConfig.cs文件中添加了以下代码

Added below code in UnityConfig.cs file

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

就是这样，解决了我的问题！

That's it, solved my problem!

这篇关于确保控制器在Web API中具有无参数的公共构造函数?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！