Hi,
You can use ModalPopup to achieve it and use JavaScript to show it dynamically.
Please try the below sample:
<script type="text/javascript">
function getTop(e)
{
var offset=e.offsetTop;
if(e.offsetParent!=null) offset+=getTop(e.offsetParent);
return offset;
}
function getLeft(e)
{
var offset=e.offsetLeft;
if(e.offsetParent!=null) offset+=getLeft(e.offsetParent);
return offset;
}
function hideModalPopupViaClient()
{
var modalPopupBehavior = $find('ModalPopupExtender');
modalPopupBehavior.hide();
}
function showModalPopupViaClient(control,id) {
$get("inputBox").innerText="You choose the item "+control.innerHTML;
var modalPopupBehavior = $find('ModalPopupExtender');
modalPopupBehavior.show();
$get(modalPopupBehavior._PopupControlID).style.left=getLeft($get('<%=DataList1.ClientID %>'))+ $get('<%=DataList1.ClientID %>').offsetWidth+"px";
$get(modalPopupBehavior._PopupControlID).style.top=getTop(control)+"px";
}
</script>
<body>
<form id="form1" runat="server">
<ajaxToolkit:ToolkitScriptManager runat="Server" ID="ScriptManager1" />
<input id="Hidden1" runat="server" type="hidden" />
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:DataList ID="DataList1" runat="server" DataSourceID="SqlDataSource1" >
<ItemTemplate>
<div style="border-color:Black;border-width:1px;border-style:solid;">
<asp:Label ID="Label1" Text='<%# Eval("CategoryID") %>' runat="server"></asp:Label>
<asp:HyperLink ID="detail" runat="server" onmouseout="hideModalPopupViaClient()" onmouseover="showModalPopupViaClient(this)">'<%# Eval("CategoryID") %>'</asp:HyperLink>
</div>
</ItemTemplate>
</asp:DataList>
</ContentTemplate>
</asp:UpdatePanel>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
SelectCommand="SELECT * FROM [Categories]"></asp:SqlDataSource>
<asp:Button runat="server" ID="showModalPopupClientButton" style="display:none"/>
<ajaxToolkit:ModalPopupExtender ID="ModalPopupExtender" runat="server"
TargetControlID="showModalPopupClientButton"
PopupControlID="programmaticPopup"
RepositionMode="None"
/>
<br />
<div CssClass="modalPopup" id="programmaticPopup" style="background-color:#EEEEEE; filter:alpha(opacity=70);opacity:0.7;display:none;width:50px;padding:10px">
<span id="inputBox" ></span>
<br />
</div>
</form>
</body>