Using WebWindowTemplateHttpHandler in v14.1 as per B222208

The WebWindowTemplateHttpHandler is not currently in use. If it is required for your particular task, make sure that it performs only what you want it to do and simply calls the ProcessRequest method of the requested page to restore the normal request processing flow.
In you case, the handler should look as follows:

Visual Basic
Public Class WebWindowTemplateCustomHttpHandler_B222208  
    Implements IHttpHandler  
    Implements IRequiresSessionState  
    Private m_actualHandler As IHttpHandler  
    Public ReadOnly Property ActualHandler() As IHttpHandler  
        Get  
            Return m_actualHandler  
        End Get  
    End Property  
#Region "IHttpHandler Members"  
    Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable  
        Get  
            Return False  
        End Get  
    End Property  
    Public Sub ProcessRequest(context As HttpContext) Implements IHttpHandler.ProcessRequest  
        Dim templateContext__1 As TemplateContext = WebApplication.Instance.RequestManager.GetTemplateContext()  
        WebApplication.CurrentRequestTemplateType = WebApplication.Instance.RequestManager.GetTemplateType()  
        If templateContext__1 <> TemplateContext.Undefined Then  
            If Not WebApplication.Instance.IsLoggedOn AndAlso templateContext__1 <> TemplateContext.LogonWindow Then  
                Dim redirectTemplate As New Page()  
                Dim script As String = RenderUtils.GetScriptHtml(String.Format("window.location.href='{0}' + '?ReturnUrl=' + encodeURIComponent(window.location.pathname + window.location.hash);", WebApplication.LogonPage))  
                redirectTemplate.Controls.Add(New LiteralControl(script))  
                redirectTemplate.ProcessRequest(context)  
                Return  
            End If  
            Dim template As IFrameTemplate = WebApplication.Instance.CreateTemplate(templateContext__1)  
            Dim page As Page = DirectCast(template, Page)  
            m_actualHandler = page  

            DirectCast(template, IHttpHandler).ProcessRequest(context)  
        Else  
            Dim unknownPage As IHttpHandler = DirectCast(System.Web.Compilation.BuildManager.CreateInstanceFromVirtualPath(context.Request.Path, GetType(Page)), IHttpHandler)  
            m_actualHandler = unknownPage  
            unknownPage.ProcessRequest(context)  
        End If  
    End Sub  
#End Region  
End Class  

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