[英]Can I get an Action's return type from an Action Filter?
我有一個ASP.NET MVC 2應用程序,我在其中創建自定義操作篩選器。 此過濾器位於應用程序中的控制器上,並從數據庫驗證該功能當前是否可用。
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
我的問題是,根據已請求的操作,我需要將用戶重定向到返回視圖,部分視圖或JSON的操作。
鑒於ActionExecutingContext,我可以找出最初請求的操作的返回類型是什么?
編輯:
好吧,我越來越近但又有另一個問題。
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
我可以使用反射來查找action方法的返回類型。 我的問題是如果我在控制器上有以下方法:
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
我拋出了一個AmbiguousMatchException。
根據我在OnActionExecuting方法中的信息,無論如何更確切地說是確定正在調用的重載?
我基於此創建了一個AuthenticationFilterAttribute,它根據類型返回不同的結果:
/// <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;
}
}
好的,這是我提出的解決方案。
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 As MethodInfo
Try
actionMethodInfo = controllerType.GetMethod(actionName)
Catch ex As AmbiguousMatchException
' Try to find a match using the parameters passed through
Dim actionParams = filterContext.ActionParameters
Dim paramTypes As New List(Of Type)
For Each p In actionParams
paramTypes.Add(p.Value.GetType())
Next
actionMethodInfo = controllerType.GetMethod(actionName, paramTypes.ToArray)
End Try
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
如果Type.GetMethod(string)調用無法識別請求的方法,我將從ActionExecutingContext.ActionParameters集合中獲取參數集合,並構建請求中傳遞的參數類型的數組。 然后,我可以使用Type.GetMethod(string,type())重載來更具體地說明我的請求。
在調用OnActionExecuting
,操作方法尚未執行,因此您無法知道該操作方法是否將返回ActionResult
哪個子類。 所以,除非你可以使用CIL分析實現(我覺得很快就會變丑),我不認為你想做什么是可能的。
也就是說,當控制器不夠用時,您是不是將用戶重定向到視圖? 我的意思是,我不明白為什么要將用戶重定向到JSON結果或部分視圖。
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