asp.net-mvc - 我可以从操作过滤器获取操作的返回类型吗？

Question

我有一个 ASP.NET MVC 2 应用程序，我正在其中创建自定义操作筛选器。该过滤器位于应用程序中的 Controller 上，并从数据库中验证该功能当前是否可用。

Public Overrides Sub OnActionExecuting(ByVal filterContext As System.Web.Mvc.ActionExecutingContext)
  Try
    ' Check controller name against database.
    Dim controllerName = filterContext.Controller.GetType().Name
    controllerName = controllerName.Remove(controllerName.Length - 10)
    ' Look up availability.
    Dim available As Boolean = _coreService.GetControllerAvailability(controllerName)
    If Not available Then
      ' Redirect to unavailable notice.
      filterContext.Result = New RedirectResult("/Home/Unavailable/")
    End If
  Catch ex As Exception
    _eventLogger.LogWarning(ex, EventLogEntryType.Error)
    Throw
  End Try
End Sub

我的问题是，根据请求的操作，我需要将用户重定向到返回 View 、部分 View 或 JSON 的操作。

给定 ActionExecutingContext，我可以找出最初请求的操作的返回类型是什么吗？

编辑:

好的，我已经接近了，但还有另一个问题。

Public Overrides Sub OnActionExecuting(ByVal filterContext As System.Web.Mvc.ActionExecutingContext)
  Try
    ' Check controller name against database.
    Dim controllerName = filterContext.Controller.GetType().Name
    Dim shortName = controllerName.Remove(controllerName.Length - 10)
    ' Look up availability.
    Dim available As Boolean = _coreService.GetControllerAvailability(shortName)
    If Not available Then
      ' find out what type is expected to be returned
      Dim actionName As String = filterContext.ActionDescriptor.ActionName
      Dim controllerType = Type.GetType("Attenda.Stargate.Web." & controllerName)
      Dim actionMethodInfo = controllerType.GetMethod(actionName)
      Dim actionReturnType = actionMethodInfo.ReturnType.Name

      Select Case actionReturnType
        Case "PartialViewResult"
          filterContext.Result = New RedirectResult("/Home/UnavailablePartial/")
        Case "JsonResult"
          filterContext.Result = New RedirectResult("/Home/UnavailableJson/")
        Case Else
          filterContext.Result = New RedirectResult("/Home/Unavailable/")
      End Select

    End If
  Catch ex As Exception
    _eventLogger.LogWarning(ex, EventLogEntryType.Error)
    Throw
  End Try
End Sub

我可以使用反射来查找操作方法的返回类型。我的问题是 Controller 上是否有以下方法:

Public Function Create() As ViewResult
  Return View()
End Function

<AcceptVerbs(HttpVerbs.Post)>
Public Function Create(values as FormCollection) As ViewResult
  ' Do stuff here
End Function

我抛出了 AmbigeousMatchException。

根据我在 OnActionExecuting 方法中获得的信息，是否可以更精确地确定正在调用的重载？

Answer 1

我基于此创建了一个 AuthenticationFilterAttribute，它根据类型返回不同的结果:

    /// <summary>
    /// Access to the action will be blocked if the user is not logged in. 
    ///  Apply this to the controller level or individual actions as an attribute.
    /// </summary>
    public class AuthenticationFilterAttribute : ActionFilterAttribute
    {
        protected const string InvalidAccess = "Invalid access";

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            // Find out if the user is logged in: 
            Controller controller = (Controller)filterContext.Controller;
            if (!controller.User.Identity.IsAuthenticated)
            {
                switch (GetExpectedReturnType(filterContext).Name)
                {
                    case "JsonResult":
                        var jsonResult = new JsonResult();
                        jsonResult.Data = new { Error = true, ErrorMessage = InvalidAccess };
                        jsonResult.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
                        filterContext.Result = jsonResult;
                        break;

                    // Assume same behaviour as ActionResult
                    default: 
                        var actionResult = new ContentResult();
                        actionResult.Content = InvalidAccess;
                        filterContext.Result = actionResult;
                        break;
                }
            }
        }

        private Type GetExpectedReturnType(ActionExecutingContext filterContext)
        {
            // Find out what type is expected to be returned
            string actionName = filterContext.ActionDescriptor.ActionName;
            Type controllerType = filterContext.Controller.GetType();
            MethodInfo actionMethodInfo = default(MethodInfo);
            try
            {
                actionMethodInfo = controllerType.GetMethod(actionName);
            }
            catch (AmbiguousMatchException ex)
            {
                // Try to find a match using the parameters passed through
                var actionParams = filterContext.ActionParameters;
                List<Type> paramTypes = new List<Type>();
                foreach (var p in actionParams)
                {
                    paramTypes.Add(p.Value.GetType());
                }

                actionMethodInfo = controllerType.GetMethod(actionName, paramTypes.ToArray());
            }

            return actionMethodInfo.ReturnType;
        }
    }