I am trying to use a modelpopup extender(from ajaxtoolkit) to display a popup in my aspx page. The modelpopup extender has been used in side a datalist.

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<form id="form1" runat="server">
<asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
</asp:ToolkitScriptManager>
<div>
<aspataList ID="DataList1" runat="server"
RepeatColumns="4" RepeatDirection="Horizontal"
onitemcommand="DataList1_ItemCommand"
onitemdatabound="DataList1_ItemDataBound">
<ItemStyle BackColor="#EFF3FB" />
<ItemTemplate>
<div >
<div >

<asp:LinkButton ID="lnk_Caption" runat="server" CommandArgument = '<%# Eval("pictureID") %>' CommandName = "Caption" > Caption
</asp:LinkButton>
<asp:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="lnk_Caption" PopupControlID="DivCaption" OkControlID="OkButton" >
</asp:ModalPopupExtender>
</div>
</ItemTemplate>
</aspataList>

</div>
<!--Pop up-->
<div runat="server" id= "DivCaption" width="150px" Height ="200px" >
<table border="0" cellspacing="0" cellpadding="0" width ="150px" >
<tr>
<td><textarea id="Textarea1" name="comment" runat="server" class="text_main_field" title="E mail" onblur="if(this.value=='') this.value='Caption here';" onfocus="if(this.value=='Caption here')this.value='';" >Caption here</textarea></td>
</tr>
<tr>
<td>
<asp:Button ID="OkButton" runat="server" Text="OK" onclick="OkButton_Click" />
<asp:Button ID="btnCancel" runat="server" Text="Cancel" onclick="btnCancel_Click" />
</td>
</tr>
</table>
</div>
</form>
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I want to execute an update statement in OkButton_Click(). for that i need the pictureid. I am not able to get the picture id of the command argument given in the "lnk_Caption". Pls help.......