Question

I’m having trouble with a certain scenario. I have a repeater control, within I have a placeholder (and for the sake of testing, I’ve placed a div and tried that as well). I would like to, in my code behind page, find that placeholder or div, and put controls in it (for now, 3 textboxes and 2 buttons)

I have no issue with adding controls to a placeholder, I understand how that works, what I can’t get here, is how to find this dynamic control here.

Here is some code snippets to help illustrate what I’m trying to do.

(the asp)

        <asp:Repeater id="rptSpecialNotes" runat="server">
        <ItemTemplate>
            <asp:UpdatePanel ID="udpSpecialNotesRepeater" runat="server">
                <ContentTemplate>
                    <asp:PlaceHolder ID="plhSpecialNotesRepeater" runat="server">
                    </asp:PlaceHolder>
                </ContentTemplate>
            </asp:UpdatePanel>
            <p><%# eval("subject") %></p>
            <div id="specialNotes" runat="server"></div>
            <asp:imagebutton runat="server" AlternateText="add Motion" ImageUrl="images/controls/Exclaim.png" width="40" height="40"></asp:imagebutton>
            <asp:imagebutton runat="server" AlternateText="add document" ImageUrl="images/controls/Documents.png" width="40" height="40"></asp:imagebutton>
            <asp:imagebutton runat="server" AlternateText="move up" ImageUrl="images/controls/Arrow-Up.png" width="40" height="40" CommandName="moveUp" CommandArgument='<%# Container.ItemIndex & "," &  eval("ItemID") %>'></asp:imagebutton>
            <asp:imagebutton runat="server" AlternateText="move down" ImageUrl="images/controls/Arrow-Down.png" width="40" height="40" CommandName="moveDown" CommandArgument='<%# Container.ItemIndex & "," &  eval("ItemID") %>'></asp:imagebutton>
            <asp:imagebutton runat="server" AlternateText="delete" ImageUrl="images/controls/Delete.png" width="40" height="40" CommandName="delete" CommandArgument='<%# Container.ItemIndex & "," &  eval("ItemID") %>'></asp:imagebutton>
            <asp:imagebutton runat="server" AlternateText="edit" ImageUrl="images/controls/Globe.png" width="40" height="40" CommandName="edit" CommandArgument='<%# Container.ItemIndex & "," &  eval("ItemID") %>'></asp:imagebutton>
        </ItemTemplate>
    </asp:Repeater>

The image button edit, hits the rptSpecialNotes_Item command, which calls a method (edit special notes) which looks something like this

    Dim commandArguments() As String = Split(e.CommandArgument, ",")
    Dim divId As String = commandArguments(0)
    Dim itemId As String = commandArguments(1)



    'determine action based on command name
    If e.CommandName = "edit" Then
        Call editSpecialNotes(itemId,divId)
    End If

and edit special notes is to place things in the given divID. For the sake of getting this to work, I’ve given divID a static value that I know exists (rptSpecialNotes_plhSpecialNotesRepeater_1) or something similar to that extent. However, I always end up with a null object reference.

Answer 1

Use FindControl to get the nested control in the rptSpecialNotes_Item event handler – this will return the control:

sender.FindControl("specialNotes")

It will return a Control type, so a cast is needed to the right type if you want to use the specific properties and methods of that type.