Hi Nahid,
Please Try this:
Ascx File:
=======
<
form id="form1" runat="server">
<div>
<asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="~/Images/register.Gif"
OnClientClick="openWinContentTemplate(); return false;" />
<telerik:RadScriptManager ID="RadScriptManager1" Runat="server">
</telerik:RadScriptManager>
</div>
<telerik:RadWindow ID="RadWindow1" runat="server">
<ContentTemplate>
<%-- Your Content here--%>
<asp:Label ID="Label1" runat="server" Text="Show the RadWindow in aspx file from Ascx"></asp:Label>
</ContentTemplate>
</telerik:RadWindow>
<script type="text/javascript">
function openWinContentTemplate()
{
var ShowRadWindow = $telerik.$('[id$="RadWindow1"]').attr("id");
var MyRadWindow = $find(ShowRadWindow);
MyRadWindow.show();
}
</script>
</form>
Aspx File:(Drag and Drop Ascx file to Aspx Page)
=========
<uc1:RadWindowControl ID="RadWindowControl1" runat="server" />