Is the Header file is a User Control ? any way you need to write a event handler in your header file like
public event SomeEventName
Add
{
}
Remove
{
}
}
See this for create a event handler
http://www.eggheadcafe.com/articles/20050710.asp
http://forums.asp.net/p/1281975/2452657.aspx
http://www.15seconds.com/issue/031023.htm
or use this
<%@ Page Language="C#" %>
<script runat="server">
protected void txtSearch_TextChanged(object sender, EventArgs e)
{
lblSearchResults.Text = "Search for: " + txtSearch.Text;
}
</script>
<html>
<head>
<title>TextBox AutoPostBack</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label
id="lblSearch"
Text="Search:"
Runat="server" />
<asp:TextBox
id="txtSearch"
AutoPostBack="true"
OnTextChanged="txtSearch_TextChanged"
Runat="server" />
<hr />
<asp:Label
id="lblSearchResults"
Runat="server" />
</div>
</form>
</body>
</html>