If you place LinkButton inside a repeater which is inside an UpdatePanel, you will get a full postback if you click on the LinkButton.

Solution?
On code behind register the linkbutton inside the repeater for Asynchronous postback.
Like this
foreach (RepeaterItem ri in rpt.Items)
{
if (ri.ItemType == ListItemType.Item || ri.ItemType == ListItemType.AlternatingItem)
{
LinkButton lb = (LinkButton)ri.FindControl("lb");
ScriptManager1.RegisterAsyncPostBackControl(lb);
}
}

Read the original article at Webcosmo Webmaster Forum http://www.webcosmoforums.com/asp/21403-linkbutton-inside-repeater-updatepanel-causes-full-postback-asp-net.html