Rank 1
I have a page that loads a list of controls based on report criteria. I've been converting some of these controls to Telerik, but I also have some controls that are custom controls. I've narrowed down the issue to when an ASP.NET control (ASP from the dropdown) gets loaded after a Telerik control (Telerik from the dropdown), I get a "Failed to load viewstate" error. It also happens if both controls are Telerik controls, but does not happen if all controls are ASP.NET controls.
DynamicControls.aspx
<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="DynamicControls.aspx.vb" Inherits="TestCode.DynamicContrls" %><%@ Register assembly="Telerik.Web.UI" namespace="Telerik.Web.UI" tagprefix="telerik" %><!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <title></title></head><body> <form id="form1" runat="server"> <div> <telerik:RadScriptManager ID="RadScriptManager1" Runat="server"> </telerik:RadScriptManager> <asp:DropDownList ID="cboCriteria" runat="server" AutoPostBack="True"> <asp:ListItem>Select a form</asp:ListItem> <asp:ListItem Value="Telerik">Form With Telerik Control</asp:ListItem> <asp:ListItem Value="ASP">Form With ASP Control</asp:ListItem> </asp:DropDownList> <br /> <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder> <br /> </div> </form></body></html>
DynamicControls.vb
Imports Telerik.Web.UIPublic Class DynamicContrls Inherits System.Web.UI.Page Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 'If Not Session("ControlsCreated") = Nothing Then CreateControl(cboCriteria.SelectedItem.Value) 'End If End Sub Private Sub CreateControl(ControlType As String) Select Case ControlType Case "Telerik" RenderTelerikControls() Case "ASP" RenderASPControls() End Select Session("ControlsCreated") = True End Sub Private Sub RenderTelerikControls() Dim txtFirst As New RadTextBox txtFirst.ID = "txtTelerik" & Guid.NewGuid.ToString PlaceHolder1.Controls.Add(txtFirst) PlaceHolder1.Controls.Add(New LiteralControl("<BR>")) End Sub Private Sub RenderASPControls() Dim txtFirst As New TextBox txtFirst.ID = "txtASP" & Guid.NewGuid.ToString PlaceHolder1.Controls.Add(txtFirst) PlaceHolder1.Controls.Add(New LiteralControl("<BR>")) End Sub Protected Sub cboCriteria_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cboCriteria.SelectedIndexChanged ' For this example, simply reload the page. End SubEnd Class2 Answers, 1 is accepted
Rank 1
To add, while I could disable the viewstate for all dynamic controls, which does work, these controls disappear when there is a postback. The purpose of the dynamic controls is to generate criteria filters for reports/queries. The problem stems from when there's a postback and new controls are being created.
1 - A dropdownlist postback is made - ASP.NET control is created.
2 - Another dropdownlist postback is made - Tries to create a telerik control and errors out.
Rank 1
Ok, I think I found it after many hours of digging around. I simple disabled the viewstate of the panel, but not the individual dynamic controls. I also found Request.Form([ControlName]) in order to get the value of the dropdown on init or load.
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Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim formValue As String = ""
If Not String.IsNullOrEmpty(Request.Form("cboCriteria")) Then
formValue = Request.Form("cboCriteria")
Response.Write("<HR>" & formValue & "<HR>")
End If
CreateControl(formValue)
End Sub