Using the UpdatePanel Control : UpdatePanel « Ajax « ASP.NET Tutorial

The UpdatePanel control updates a portion of a page without updating the entire page. 

<%@ Page Language="C#" %>
<!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>UpdatePanel Simple</title>
</head>
<body>
    <form id="form1" runat="server">

    <asp:ScriptManager ID="ScriptManager1" runat="server" />

    Page Time: <%= DateTime.Now.ToString("T") %>
    <br /><br />

    <asp:UpdatePanel
        id="up1"
        runat="server">
        <ContentTemplate>
        UpdatePanel Time: <%= DateTime.Now.ToString("T") %>
        <br />
        <asp:Button
            id="btn"
            Text="Update"
            runat="server" />
        </ContentTemplate>
    </asp:UpdatePanel>

    </form>
</body>
</html>

20.11.UpdatePanel
	20.11.1.	Using the UpdatePanel Control
	20.11.2.	Entering customer feedback into an Ajax-enabled form.
	20.11.3.	Specifying UpdatePanel Triggers
	20.11.4.	Nesting UpdatePanel Controls
	20.11.5.	Updating UpdatePanels Programmatically
	20.11.6.	UpdatePanels and JavaScript
	20.11.7.	Show Alert UpdatePanel
	20.11.8.	UpdatePanel Server-Side Page Execution Lifecycle
	20.11.9.	UpdatePanel Client-Side Page Execution Lifecycle
	20.11.10.	UpdatePanel Custom Progress