F＃Web API中的IDependencyResolver接口實現

Question

我正在使用F＃重新編寫C＃ASP.NET Web API應用程序。我已經完成了模型和控制器，並且移至執行IDependencyResolver的MyDependencyResolver。

我有實施GetService方法，其簽名在C＃是一個問題：

object GetService(System.Type serviceType) 

所以我需要返回一個obj並採取System.Type作爲參數。

這是我迄今爲止在F＃：

type MyDependencyResolver() = 
    interface System.Web.Http.Dependencies.IDependencyResolver with 
     member this.BeginScope() : IDependencyScope = 
      this :> IDependencyScope 

     member this.GetService(serviceType:Type) : obj = 

      if (serviceType = typeof<Controllers.HomeController>) then 
       let homeController = new Controllers.HomeController(arg1, arg2, arg3, arg4) 
       homeController :> obj 
      // ??? 
      elif (serviceType = typeof<_>) then 
       null   

     member this.GetServices (serviceType: Type) :IEnumerable<obj> = 
      let x = new List<obj>() 
      x :> IEnumerable<obj> 

     member this.Dispose() = 
      () 

所以，如果serviceType是HomeController型我想返回的HomeController一個實例，如果它是任何其他類型的我想返回null。我如何在F＃中做到這一點？

編輯：

GetService方法在C＃：

public object GetService(Type serviceType) 
{ 
    if (serviceType == typeof(Controllers.HomeController)){ 
     return new Controllers.HomeController(arg1, arg2, arg3, arg4); 
    } 
    return null; 
} 

Answer 1

你可以只使用Activator.CreateInstance(serviceType)但你從哪裏得到的構造函數的參數？

在我的項目我使用Unity，其配置如下：

let private ConfigureUnity (config : HttpConfiguration) = 
     let rec unityResolver (container : IUnityContainer) = 
      { new IDependencyResolver with 
       member this.BeginScope() = 
        unityResolver(container.CreateChildContainer()) :> IDependencyScope 
       member this.GetService serviceType = 
        try container.Resolve(serviceType) with 
         | :? ResolutionFailedException -> null 
       member this.GetServices serviceType = 
        try container.ResolveAll(serviceType) with 
         | :? ResolutionFailedException -> Seq.empty 
       member this.Dispose() = container.Dispose() 
      } 

     config.DependencyResolver <- (new UnityContainer()) 
      .RegisterType<IFoo, FooImplementation>(new HierarchicalLifetimeManager()) 
      .RegisterType<IBar, BarImplementation>(new HierarchicalLifetimeManager()) 
      |> unityResolver 

類（如您的控制器），然後自動解析和Unity將爲您創建依賴（構造函數的參數）。使用其他依賴注入框架應該很簡單。