protected void btnCategory_Click(object sender, System.Web.UI.ImageClickEventArgs e)
{
for (int i = 0; i < cblCategory.Items.Count; i++)
{
if (cblCategory.Items[i].Selected)
{
Response.Write("SelectedCategory:" + cblCategory.Items[i].Text );
}
}
}
and if it doesnot works then try using 'findcontrol'