ASP.NET provides a mechanism for caching portions of pages, called page fragment caching. To cache a portion of a page, you must first encapsulate the portion of the page you want to cache into a user control. In the user control source file, add an OutputCache directive specifying the Duration and VaryByParam attributes. When that user control is loaded into a page at runtime, it is cached, and all subsequent pages that reference that same user control will retrieve it from the cache.

<!— UserControl.ascx —>

<%@ OutputCache Duration='60'
VaryByParam='none' %>
<%@ Control Language="'C#'" %>

<script runat="server">
protected void Page_Load(Object src, EventArgs e)
{
_date.Text = "User control generated at " +
DateTime.Now.ToString();
}
</script>
<asp:Label id='_date' runat="'server'" />

Here I have user caching on user control, so when ever we used in a page , only partial page will be cached.

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Fragment Caching in asp.net

• Fragment caching refers to the caching of individual user controls within a Web Form. 
• Each user control can have independent cache durations and implementations of how the caching behavior is to be applied.
• Fragment caching is useful when you need to cache only a subset of a page. 
• Navigation bars, header, and footers are good candidates for fragment caching.