c#datagridview保存问题

c#在填写单价之后查询单价消失是为什么？

查询代码：

private void tsbreferml_Click(object sender, EventArgs e)
        {
            String material = tstxtmaterial.Text.Trim();
            String connString = "Data Source=.;Initial Catalog=水利建筑工程预算定额;Integrated Security=True";
            SqlConnection conn = new SqlConnection(connString);
            conn.Open();
            String sql = "select material_cd,material_nm,material_class,material_unit,material_price from MaterialInfo where material_nm like'%" + material + "%'";
            ds2 = new DataSet();
            DataTable dtml = new DataTable("MaterialInfo");
            ds2.Tables.Add(dtml);
            adapter2 = new SqlDataAdapter(sql, conn);
            adapter2.Fill(ds2, "MaterialInfo");
            dgvmaterial.DataSource = ds2.Tables["MaterialInfo"];
            conn.Close();
        }

你都没保存价格，又从数据库查询绑定了数据源。