值不能为空。参数名称：key

Question

值不能为空。参数名称：key

自从我将 StructureMapControllerFactory 实现为我的 DefaultControllerFactory 以来，我已经开始收到此错误。

实际上我从 MVC Sample App StoreFront 复制了代码，但我不明白为什么这个错误不断弹出。即使出现此错误，应用程序仍然运行。

这个错误的原因可能是什么？

谢谢你的时间

---

System.ArgumentNullException was unhandled by user code
  Message="Value cannot be null.\r\nParameter name: key"
  Source="mscorlib"
  ParamName="key"
  StackTrace:
       at System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
       at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
       at System.Collections.Generic.Dictionary`2.ContainsKey(TKey key)
       at StructureMap.Util.Cache`2.get_Item(KEY key)
       at StructureMap.BuildSession.CreateInstance(Type pluginType)
       at StructureMap.Container.GetInstance(Type pluginType)
       at StructureMap.ObjectFactory.GetInstance(Type pluginType)
       at Yacht.Web.Controllers.StructureMapControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) in D:\Documents\WebSites\JOBS\Yacht\Yacht.Web\Controllers\StructureMapControllerFactory.cs:line 16
       at System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName)
       at System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory)
       at System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state)
       at System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state)
       at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData)
       at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
       at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
  InnerException: 

这是 StructureMapControllerFactory 类

public class StructureMapControllerFactory : DefaultControllerFactory
    {
        protected override IController GetControllerInstance(System.Web.Routing.RequestContext requestContext, Type controllerType)
        {
            return ObjectFactory.GetInstance(controllerType) as Controller;
        }
    }

Answer 1

另请注意，如果模型定义的属性未映射到数据库字段，则可能会发生此错误。追踪这个问题有点麻烦，所以我会留下一个答案，以防其他人遇到同样的问题。

我的修复很简单，包括 DataAnnotations：

using System.ComponentModel.DataAnnotations;

然后在特定属性上使用 NotMapped 注解：

[NotMapped]
public string SomeCustomProperty { get; set; }

Answer 2

请参阅护士对“无效控制器时的 StructureMap 错误”的回答。