问ASP.NET MVC:如何为异常过滤器创建ViewData

EN

    <AttributeUsage(AttributeTargets.Class Or AttributeTargets.Method, _
    Inherited:=True, AllowMultiple:=False)> _
    Public Class HandleRuleViolationExceptionAttribute
        Inherits FilterAttribute
        Implements IExceptionFilter

        Private m_View As String
        Private m_MasterPage As String

        Public Property View() As String
            Get
                Return m_View
            End Get
            Set(ByVal value As String)
                m_View = value
            End Set
        End Property

        Public Property MasterPage() As String
            Get
                Return If(m_MasterPage, String.Empty)
            End Get
            Set(ByVal value As String)
                m_MasterPage = value
            End Set
        End Property

        Public Sub OnException(ByVal filterContext As System.Web.Mvc.ExceptionContext) _
                Implements System.Web.Mvc.IExceptionFilter.OnException
            If filterContext Is Nothing Then 
                Throw New ArgumentException("filterContext is null")
            End If

            'Ignore if the error is already handled.
            If filterContext.ExceptionHandled Then Return

            'Handle only ObjectIsInvalidExceptions.
            If Not TypeOf filterContext.Exception Is ObjectIsInvalidException Then
                Return
            End If

            Dim ex As ObjectIsInvalidException = DirectCast(filterContext.Exception, ObjectIsInvalidException)

            'If this is not an HTTP 500 (for example, if somebody throws an HTTP 404 from an action method),
            'ignore it.
            If (New HttpException(Nothing, ex).GetHttpCode()) <> 500 Then Return

            Dim actionName As String = CStr(filterContext.RouteData.Values("action"))
            Dim viewName As String = If(String.IsNullOrEmpty(View), actionName, View)

            Dim viewData = filterContext.Controller.ViewData
            viewData.Model = ex.Object
            For Each item As String In filterContext.HttpContext.Request.Form.Keys
                viewData.Add(item, filterContext.HttpContext.Request.Form.Item(item))
            Next
            For Each ruleViolation In ex.Object.GetRuleViolations()
                viewData.ModelState.AddModelError(ruleViolation.PropertyName, ruleViolation.ErrorMessage)
            Next
            filterContext.Result = New ViewResult() With _
            { _
                    .ViewName = viewName, _
                    .MasterName = MasterPage, _
                    .ViewData = viewData, _
                    .TempData = filterContext.Controller.TempData _
            }
            filterContext.ExceptionHandled = True
            filterContext.HttpContext.Response.Clear()
            filterContext.HttpContext.Response.StatusCode = 500

            'Certain versions of IIS will sometimes use their own error page when
            'they detect a server error. Setting this property indicates that we
            'want it to try to render ASP.NET MVC's error page instead.
            filterContext.HttpContext.Response.TrySkipIisCustomErrors = True
        End Sub
    End Class