private void LoadProductInfoByCatId(int p, TreeNodeCollection tnc)
 {
     ProductInfoBLL bll = new ProductInfoBLL();
     List<ProductInfo> list = bll.GetProductInfoByCatId(p);
     for(int i=0; i<list.Count; i++)
     {
         tnc.Add(list[i].ProName + "====="+list[i].ProPrice+"元");
     }
 }
 private void cmbCategory_SelectedIndexChanged(object sender, EventArgs e)
 {
     if(cmbCategory.SelectedIndex !=0)
     {
         int id = Convert.ToInt32(cmbCategory.SelectedValue);
         ProductInfoBLL bll = new ProductInfoBLL();
         dgvProductInfo.AutoGenerateColumns = false;
         dgvProductInfo.DataSource = bll.GetProductInfoByCatId(id);
         if(dgvProductInfo.SelectedRows.Count>0)
         {
             dgvProductInfo.SelectedRows[0].Selected = false;
         }
         
     }
     else
     {
         LoadProductInfoByDelFlag(0);
     }
 }