RuntimeBinderException - C＃.NET 4動態關鍵字 - 幫助我理解為什么方法不匹配

Question

我為HttpModule構建了一個通用的配置系統，允許可插入的HTTP頭檢查器。 作為參考，這里是代碼的基本布局 - 這應該足以讓我感覺到我在做什么：

public interface IHttpHeaderInspectingAuthenticatorFactory<T>
    where T: HttpHeaderInspectingAuthenticatorConfigurationElement
{
    IHttpHeaderInspectingAuthenticator<T> Construct(T config);
}

public class BasicAuthenticationInspectingAuthenticatorFactory :
    IHttpHeaderInspectingAuthenticator<BasicAuthenticationHeaderInspectorConfigurationElement>
{
    public IHttpHeaderInspectingAuthenticator<BasicAuthenticationHeaderInspectorConfigurationElement> Construct(BasicAuthenticationHeaderInspectorConfigurationElement config)
    {
        return new BasicAuthenticationInspectingAuthenticator(config);
    }
}

public class BasicAuthenticationInspectingAuthenticator : HttpHeaderInspectingAuthenticatorBase<BasicAuthenticationHeaderInspectorConfigurationElement>
{
    internal BasicAuthenticationInspectingAuthenticator(BasicAuthenticationHeaderInspectorConfigurationElement config) 
        : base(config) {}

 //snip -- IHttpHeaderInspectingAuthenticator<T> and IHttpHeaderInspectingAuthenticator implementation
}


public class BasicAuthenticationHeaderInspectorConfigurationElement : HttpHeaderInspectingAuthenticatorConfigurationElement
{
 //extra properties
}


public class HttpHeaderInspectingAuthenticatorConfigurationElement : ConfigurationElement
{
 protected override void PostDeserialize()
 {
     base.PostDeserialize();

     //simple verification of info supplied in config
     var t = Type.GetType(Factory);
     if (null == t)
         throw new ConfigurationErrorsException(String.Format("The factory type specified [{0}] cannot be found - check configuration settings", Factory ?? ""));

     if (!typeof(IHttpHeaderInspectingAuthenticatorFactory<>).IsGenericInterfaceAssignableFrom(t))
         throw new ConfigurationErrorsException(String.Format("The factory type specified [{0}] must derive from {1} - check configuration settings", Factory ?? "", typeof(IHttpHeaderInspectingAuthenticatorFactory<>).Name));

     var c = t.GetConstructor(Type.EmptyTypes);
     if (null == c)
         throw new ConfigurationErrorsException(String.Format("The factory type specified [{0}] must have a parameterless constructor - check configuration settings", Factory ?? ""));
 }

 [ConfigurationProperty("factory", IsRequired = true)]
 public string Factory
 {
  get { return (string)this["factory"]; }
  set { this["factory"] = value; }
 }

 //this allows us to use types derived from HttpHeaderInspectingAuthenticatorConfigurationElement
    protected override bool OnDeserializeUnrecognizedAttribute(string name, string value)
    {                    
        ConfigurationProperty property = new ConfigurationProperty(name, typeof(string), value);
        Properties.Add(property);
        base[property] = value;            
        return true;
    }

 public IHttpHeaderInspectingAuthenticator GetInspector()
 {
     dynamic factoryInstance = Activator.CreateInstance(Type.GetType(Factory));
     return factoryInstance.Construct(this);
 }
}

現在問題發生在GetInspector調用中 - 所提供的Factory名稱的所有實例必須實現IHttpHeaderInspectingAuthenticatorFactor <>（如PostDeserialize中的規范）。 因此，它們都將具有Construct方法，其中提供的類型T實際上將是實現GetInspector（）方法的類的實際類型。 因此，例如，將在BasicAuthenticationHeaderInspectorConfigurationElement的實例上調用GetInspector - 因此'this'將是BasicAuthenticationHeaderInspectorConfigurationElement的實例。

但是，對Construct的調用失敗。 它找到方法很好，但顯然參數類型不匹配基於拋出的RuntimeBinderException。 基於CallSite.Target，看起來動態代理期望的預期類型是HttpHeaderInspectingAuthenticatorConfigurationElement - 我傳遞的'this'是從該基礎派生的BasicAuthenticationHeaderInspectorConfigurationElement。

什么給出了什么？ 我在這里沒有得到什么嗎？ 我嘗試傳遞（這是動態的）或（（HttpHeaderInspectingAuthenticatorConfigurationElement）） - 但兩者都失敗了同樣的問題。

Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: The best overloaded method match for 'Redcated.Authentication.BasicAuthenticationInspectingAuthenticatorFactory.Construct(Redcated.Authentication.Configuration.BasicAuthenticationHeaderInspectorConfigurationElement)' has some invalid arguments
  at CallSite.Target(Closure , CallSite , Object , HttpHeaderInspectingAuthenticatorConfigurationElement )
  at System.Dynamic.UpdateDelegates.UpdateAndExecute2[T0,T1,TRet](CallSite site, T0 arg0, T1 arg1)
  at Redcated.Authentication.Configuration.HttpHeaderInspectingAuthenticatorConfigurationElement.GetInspector() in D:\Users\ebrown\Documents\Visual Studio 2010\Projects\Utility\source\Authentication Library\Configuration\HttpHeaderInspectingAuthenticatorConfigurationElement.cs:line 79
  at Redcated.Authentication.Configuration.HttpHeaderInspectingAuthenticatorConfigurationElementCollection.<GetInspectors>b__0(HttpHeaderInspectingAuthenticatorConfigurationElement i) in D:\Users\ebrown\Documents\Visual Studio 2010\Projects\Utility\source\Authentication Library\Configuration\HttpHeaderInspectingAuthenticatorConfigurationElementCollection.cs:line 78
  at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
  at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer)
  at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector)
  at Redcated.Authentication.HttpHeaderInspectingAuthenticationModule.AuthenticateRequest(Object sender, EventArgs e) in D:\Users\ebrown\Documents\Visual Studio 2010\Projects\Utility\source\Authentication Library\HttpHeaderInspectingAuthenticationModule.cs:line 49
  at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
  at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

僅供參考 - 我通過改變接口的架構來解決這個問題：

public interface IHttpHeaderInspectingAuthenticatorFactory
{
    IHttpHeaderInspectingAuthenticator Construct(HttpHeaderInspectingAuthenticatorConfigurationElement config);
}

public interface IHttpHeaderInspectingAuthenticatorFactory<T> : IHttpHeaderInspectingAuthenticatorFactory
    where T: HttpHeaderInspectingAuthenticatorConfigurationElement
{
    IHttpHeaderInspectingAuthenticator<T> Construct(T config);
}

public abstract class HttpHeaderInspectingAuthenticatorFactoryBase<T> : IHttpHeaderInspectingAuthenticatorFactory<T>
            where T : HttpHeaderInspectingAuthenticatorConfigurationElement
{
    protected static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

    public abstract IHttpHeaderInspectingAuthenticator<T> Construct(T config);

    public IHttpHeaderInspectingAuthenticator Construct(HttpHeaderInspectingAuthenticatorConfigurationElement config)
    {
        return Construct((T)config);
    }
}

 public class BasicAuthenticationInspectingAuthenticatorFactory :
    HttpHeaderInspectingAuthenticatorFactoryBase<BasicAuthenticationHeaderInspectorConfigurationElement>
{
    public override IHttpHeaderInspectingAuthenticator<BasicAuthenticationHeaderInspectorConfigurationElement> Construct(BasicAuthenticationHeaderInspectorConfigurationElement config)
    {
        return new BasicAuthenticationInspectingAuthenticator(config);
    }
}

然后，當然，GetInspector調用變為

public IHttpHeaderInspectingAuthenticator GetInspector()
{
    var factoryInstance = (IHttpHeaderInspectingAuthenticatorFactory)Activator.CreateInstance(Type.GetType(Factory));
    return factoryInstance.Construct(this);
}

所以我認為我的理解必定會有所失誤...希望有人可以解釋一下。

謝謝！

Answer 1

我認為你需要把this變成動態的。 例如factoryInstance.Construct((dynamic)this); 我認為問題在於動態調用默認使用緩存委托（Target）簽名的編譯時信息。

由於動態調用的實現是在基類中，它是用於簽名的，但是因為你的后期綁定簽名是一個子類，你不能去HttpHeaderInspectingAuthenticatorConfigurationElement - > BasicAuthenticationHeaderInspectorConfigurationElement ，因此通過將參數轉換為動態你告訴DLR參數類型是在運行時確定的。

Answer 2

你是這樣說的：

 dynamic factoryInstance = Activator.CreateInstance(Type.GetType(Factory));
 dynamic parameter = this;
 return factoryInstance.Construct(parameter); 

不工作？