Hi rsmldmv,
Please refer below sample.
HTML
WebUserControl.ascx
<%@ Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl.ascx.cs"
Inherits="WebUserControl" %>
<asp:DropDownList ID="ddlFruits" runat="server" onchange="GetSelectedTextValue(this)">
<asp:ListItem Text="Mango" Value="1"></asp:ListItem>
<asp:ListItem Text="Grapes" Value="2"></asp:ListItem>
<asp:ListItem Text="Banana" Value="3"></asp:ListItem>
<asp:ListItem Text="Apples" Value="4"></asp:ListItem>
</asp:DropDownList>
WebUserControl2.ascx
<%@ Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl2.ascx.cs"
Inherits="WebUserControl2" %>
<asp:Label ID="lblMessage" runat="server"></asp:Label>
Default.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register Src="~/WebUserControl.ascx" TagPrefix="uc1" TagName="WebUserControl" %>
<%@ Register Src="~/WebUserControl2.ascx" TagPrefix="uc2" TagName="WebUserControl" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script type="text/javascript">
function GetSelectedTextValue(ddlFruits) {
var selectedText = ddlFruits.options[ddlFruits.selectedIndex].value;
document.getElementById('WebUserControl2_lblMessage').innerHTML = selectedText;
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<uc1:WebUserControl runat="server" ID="WebUserControl1" />
<uc2:WebUserControl runat="server" ID="WebUserControl2" />
</div>
</form>
</body>
</html>
Screenshot
