Update Panel error: Control with the ID “xxx” could not be found in the UpdatePanel

Question

I have a composite drop down calendar user control that consists of a textbox and and calendar image and a validation control. I expose a property called \"TextBox\" on the

Answer 1

Add The Trigger Before Page_Load, ex. Page_Init.

Answer 2

You may want to try:

...
trigger.ControlID = dtmDateFirstEntry.TextBox.ID
trigger.EventName = "TextChanged"
...

that is, use the ID instead of the ClientID for the ControlID and do not use the "On" prefix for the EventName.

Answer 3

For an html control runat server inside of an update panel you need to dereference the update panel to get a handle to the control on the server side:

using System.Web.UI.HtmlControls;

HtmlControl x = (HtmlControl)this.MyUpdatePanel.FindControl("MyHtmlControl");

Answer 4

ASPX Page:

<asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
    <asp:UpdatePanel ID="upIntendedStay" runat="server" UpdateMode="Conditional">
        <ContentTemplate>
             <uc1:DropDownCalendar ID="DropDownCalendar1" runat="server" />
            <asp:Label ID="Label4" runat="server" Text="Update tHis text from server" CssClass="ErrorText"></asp:Label>

        </ContentTemplate>
    </asp:UpdatePanel>
</asp:Content>

Code behind:

If Not Page.IsPostBack Then

    Dim trigger As New AsyncPostBackTrigger
    TextBox3.AutoPostBack = True
    trigger.ControlID = TextBox3.ID
    trigger.EventName = ""
    upIntendedStay.Triggers.Add(trigger)

    Dim trigger2 As New AsyncPostBackTrigger
    DropDownCalendar1.TextBox.AutoPostBack = True
    trigger2.ControlID = DropDownCalendar1.ID
    trigger2.EventName = "DateChanged"
    upIntendedStay.Triggers.Add(trigger2)

End If

Label4.Text = Now.ToString

And add this event to your user control:

Public Event DateChanged(ByVal sender As Object, ByVal e As System.EventArgs)

..and viola!

Answer 5

According what I understand the textbox is embedded on User Control dtmDateFirstEntry. You CANNOT use directly a control contained by a user control. The user control MUST expose the events of his child controls if you want to use them as triggers.

<asp:UpdatePanel ID="upIntendedStay" runat="server" UpdateMode="Conditional">
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="dtmDateFirstEntry" EventName="DateChanged" />
    </Triggers>
    <ContentTemplate>
        <asp:Label ID="Label4" runat="server" Text="Update tHis text from server" CssClass="ErrorText"></asp:Label>
    </ContentTemplate>
</asp:UpdatePanel>

DateChanged would be an event exposed by dtmDateFirstEntry. Do you know how to do this?