Hi!!! due to update panel i think postback of button is stuck... but you can bind datalist here the code ,,,,
public void btn_click()
{
da = new SqlDataAdapter("select ItemCode,ItemDesc, ItemCode + '-0.jpg' as PicFileName, convert(char, MRP,1) as MRP, convert(char,OfferPrice,1) as OfferPrice, DiscountPercent from Items", con);
dt = new DataTable();
da.Fill(dt);
DataList1.DataSource = dt;
DataList1.DataBind();
}