Question

I am creating a web control by addin the html in the code behind, like this:

Dim sb As New StringBuilder
Dim myDiv As HtmlGenericControl = Me.theContainer

sb.Append("<table width='100%'  cellpadding='0' cellspacing='0' style='border:0px;'>" & vbCrLf)
sb.Append(" <tr class='mainRow1'>" & vbCrLf)
sb.Append("<td  align='left'  style='border:0px solid white;'>Main Menu</td>" & vbCrLf)
sb.Append("<td>" & vbCrLf)
sb.Append("<asp:Label ID='Label1' runat='server' Text='Label'></asp:Label>" & vbCrLf)
sb.Append("</td>" & vbCrLf)
sb.Append("<td  align='right' style='border:0px solid white;'>Sort By: Id | Name</td>" & vbCrLf)
sb.Append("</tr>" & vbCrLf)
sb.Append("</table>" & vbCrLf)

myDiv.InnerHtml = sb.ToString

This will generate the html for the table in the codebehind then inject it into the specified DIV element. My question is, if I create a control in this manner, how do I add an event that will fire a method in my codebehind? For example, if I want to create a image button I would do it this way in the code:

<asp:ImageButton CommandArgument='<%# (Container.DataItem.objectValue) %>'            
ID='ImageButton1' runat='server' OnCommand='Button1_Click' ImageUrl='~/images/folder.gif' />

but in the code behind I would do this:

sb.Append("<input type='image' name='ctl00$ContentPlaceHolder1$importWizard1$folderControl1$folderRepeater$ctl04$ImageButton" & myCounter & "'")
sb.Append(" id='ctl00_ContentPlaceHolder1_importWizard1_folderControl1_folderRepeater_ctl04_ImageButton" & myCounter & "'")
sb.Append(" src='images/folder.gif' style='border-width:0px;'  />" & vbCrLf)

My question is, considering that I am generating the control on the server, how do I add an “onCommand” event that would fire a specific method on the server? I’m not looking to just cause the page to reload. This functionality is in a user control (ascx file) that is in a update pannel. I just want the update pannel to post back, not the whole page. When I view the source of a image button, or any button, with an ONCommand event, it is acutally not even in teh code behind.

Any help would be great. Oh, I am developing with Visual studio 2005

Thanks
jason

if I try to add a server control like this:

Dim img As New ImageButton
img.Command = New CommandEventHandler(AddressOf Button1_Click)

img.ID = "button-" & item.directoryName & "-" & item.objectValue
Dim newSb As StringBuilder = New StringBuilder()
Dim tw As StringWriter = New StringWriter(newSb)
Dim hw As HtmlTextWriter = New HtmlTextWriter(tw)
img.RenderControl(hw)

the “img.Command ” gives me an error (blue squigley line) saying “Public Event Command(sender as object, e as webcontrols.commandEventArgs) is an event and cannot be called directly. use a raise event statement to raise an event”

Dim img As New ImageButton()
img.ID = "button-" & item.directoryName & "-" & item.objectValue
img.ImageUrl = "images/folder.gif"
AddHandler img.Click, AddressOf img_Click

Dim newSb As StringBuilder = New StringBuilder()
Dim tw As StringWriter = New StringWriter(newSb)
Dim hw As HtmlTextWriter = New HtmlTextWriter(tw)

img.RenderControl(hw)
sb.Append(tw.ToString)

Protected Sub img_Click(ByVal sender As Object, ByVal e As ImageClickEventArgs)
    ...
End Sub

Although this seem to render fine (when I view the source) the method is never actually called.

Answer 1

So, i figured it out and wanted to post in case anyone else is trying to do this:

1. on the client side, add this javascript function:

    function UpdPanelUpdate(value){   
    var obj = document.getElementById("<%= text.ClientID %>");   
    obj.value=value;  
     __doPostBack("ctl00$ContentPlaceHolder1$importWizard1$folderControl1$button","");
    }
   

2. on the client side, add these controls:

     <asp:TextBox ID="text" runat="server" style="display:none;"></asp:TextBox>
     <asp:Button ID="button" runat="server" OnClick="Button1_Click" CommandArgument="" style="display:none;"/>
   

3. On the client page, add this updatedate panel with triggers:

   <asp:UpdatePanel ID="UpdatePanel1" runat="server"  UpdateMode="Conditional">
   <ContentTemplate>
       <div runat="server" id="theContainer" style="position:relative; border:1px solid grey; width:51em; height:28.8em; overflow:auto; align:left;"> 
           <asp:TextBox  runat="server" ID="currentIdTb" Visible="false"></asp:TextBox>     
       </div>
   </ContentTemplate>
   <Triggers>
     <asp:AsyncPostBackTrigger ControlID="button" EventName="Click" />
     </Triggers>
    </asp:UpdatePanel>
   

4. in the codebehind, add this handler:

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
     'code here
    end sub
   

5. last, in the codebehind, add an onclick even to call the js function.

      sb.Append("<input type='image' name='b" & myCounter & "'")
           sb.Append(" id='b" & myCounter & "'")
           sb.Append(" src='images/folder.gif' style='border-width:0px;' ")
           sb.Append(" onClick=""UpdPanelUpdate('" & item.objectValue & "')""  />" &   vbCrLf)