Ok, here is my situation. I have a dynamic TextBox that is added to the UpdatePanel. I need to be able to set the value of that textbox on the UpdatePanel refresh. I'm able to do that with Label control but not with the TextBox. Is that a known issue, is there a workaround? I assume i can use the standard input control possibly, but due to my project i have to use pre existing set of user controls which use TextBox. Any help is appriciated. The code is included below:
Short explanation of the example:
Example provides a link to refresh the UpdatePanel. On refresh two controls are added to the collection with specified value which is the Current time. One control is textbox and the other one is label. If you keep hitting refresh the value of the Label is changed while the value of the TextBox remains the same. Example output:test //5/11/2007 1:57:52 PM
Thanks!
<%@dotnet.itags.org. Page Language="C#" AutoEventWireup="true" %><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <title>Untitled Page</title></head><script runat="server"> protected void Page_Load(object sender, EventArgs e) { TextBox textBox = new TextBox(); textBox.Text = DateTime.Now.ToString(); Label label = new Label(); label.Text = DateTime.Now.ToString(); test.Controls.Clear(); test.Controls.Add(textBox); test.Controls.Add(label); }</script><script type="text/javascript"> function UpdateDialogControl(val) { var ctrl = $get('<%=DialogTrigger.ClientID%>'); ctrl.value = val; __doPostBack('<%=DialogTrigger.UniqueID%>',''); }</script><body> <form id="form1" runat="server"> <a href="javascript:UpdateDialogControl(1)">test</a> <asp:HiddenField runat="server" ID="DialogTrigger" /> <asp:ScriptManager ID="ScriptManager1" EnablePartialRendering="true" runat="server" /> <asp:UpdatePanel UpdateMode="Conditional" ID="CenterContentPanel" runat="server" RenderMode="Inline"> <Triggers> <asp:AsyncPostBackTrigger ControlID="DialogTrigger" /> </Triggers> <ContentTemplate> <asp:PlaceHolder runat="server" ID="test"></asp:PlaceHolder> </ContentTemplate> </asp:UpdatePanel> </form></body></html>In Page_Load Event, Put all the statement into the !IsPostBack block.
if (!IsPostBack)
{
//all the code
}
Okay ... the controls are not displayed at all on the refresh.
Textbox's update their value based on the posted value from the previous request. So you're adding it, then its getting updated, overwriting your set value. Disabling ViewState will not affect this, since the value comes from the posted values collection, not viewstate.
Normally TextBox's are updated by the time you get to OnLoad, but since this TextBox didn't exist at that time, it isn't updated until AFTER OnLoad.
So -- heres what you do...
Add the TextBox in OnInit instead. Then in OnLoad, you can set the value to whatever you want, knowing full well that the posted value has already been loaded.
I recommend you follow the link to my blog and read about dynamic controls :)
Hi, thanks for the answer. However ... I do understand how ViewState works and that you need to add controls dynamically during or before OnInit event in order for them to keep track of viewstate. Your solution will indeed work for that specific example. I need an ability to remove all the controls and add completely new ones on refresh with values i specified.
Actually this specific problem is not related to ViewState at all. Its the POST state of the textbox that is in question here. Even if you turned off viewstate to the entire page this same solution would apply. Dynamically added controls can keep track of their own viewstate no matter when you add them to the tree (as long as its before SaveViewState, which is between PreRender and Render).
If what you want is to destroy all the existing controls and start with fresh ones, its ok to clear to the control tree and start a new one -- but you have to give the existing controls a chance to load their prior state first, so that they "consume" that data. So you would do this in Load, or in response to an event (like a click event, which would be raised after Load).
So you are saying i have to add old controls before load event then in OnLoad even clear the controls collection and add new elements with a values i specified? (in the example above i'm adding controls in the Onload event).
BTW, I did not have the same problem without UpdatePanel it seems like it is adding extra remember state feature ...
Thanks for replies btw.
Nm, UpdatePanel does behave like any other control. It is not related to any extra remember state feature ... I guess i never encountered problem when i needed to completely refresh controls and yes you are right I did it on the SelectedIndex changed event before which worked fine. Now i need to do it on UpdatePanel refresh and this is where i'm having issues.
Thanks for the post again. I indeed needed to rebind the form on the event. So in case of UpdatePanel it was the ValueChanged event for the hidden input control. Just like you told the viewstate is restored when form is bound on OnLoad event and then when i bind it second time i can put new values for the controls.
Thanks!
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