我有一个ASP.NET MVC 2应用程序，我在其中创建自定义操作过滤器。此过滤器位于应用程序中的控制器上，并从数据库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，根据已请求的操作，我需要将用户重定向到返回视图，部分视图或JSON的操作。
鉴于ActionExecutingContext，我可以找出最初请求的操作的返回类型是什么？
编辑：
好吧，我越来越近了，但又有另一个问题。
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动作方法的返回类型。我的问题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
我抛出了一个AmbiguousMatchException。
使用OnActionExecuting方法中的信息，无论如何更确切地确定正在调用的重载？
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;
}
}
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;
}
}
好的，这是我提出的解决方案。
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）调用无法识别请求的方法，我将从ActionExecutingContext.ActionParameters集合中获取参数集合，并构建请求中传递的参数类型的数组。然后我可以使用Type.GetMethod（string，type（））重载来更具体地说明我的请求。
到...的时候 OnActionExecuting 在调用时，action方法还没有被执行，所以你无法知道该action方法是否会返回哪个子类 ActionResult。所以，除非你可以使用CIL分析实现（我觉得很快就会变丑），我不认为你想做什么是可能的。
也就是说，当控制器不够用时，是不是将用户重定向到视图？我的意思是，我不明白为什么要将用户重定向到JSON结果或部分视图。