User-707554951 posted
Hi anooshiravan
You should call pageload function,
code as below:
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="WebUserControl3.ascx.cs" Inherits="CaseTest.CaseTest.WebUserControl3" %>
<script type="text/javascript">
function pageLoad(sender, e)
{
alert("1234");
}
pageLoad();
</script>
<asp:TextBox ID="TextBox1" runat="server" Text =" Control in user control"></asp:TextBox>
<form id="form1" runat="server">
<div>
<uc1:WebUserControl3 runat="server" id="WebUserControl3" />
</div>
</form>
Output:

Best regards
Cathy