问使用组合框中选定的文本更改sql查询

EN

using(MySqlConnection con = new MySqlConnection(cs))
{
      con.Open();
      //string command;

      string command = @"SELECT * FROM `db_liq_blnd_calc_sys`.`tbl_vat_12_spirit_sa` WHERE DIP = '" + txt_Calc_BULK_DIP.Text + "' AND SLIDE = '" + txt_Calc_BULK_SLIDE.Text + "'";
      MySqlDataAdapter da = new MySqlDataAdapter(command, con);
      DataTable dtable = new DataTable();
      DataSet ds = new DataSet();
      da.Fill(ds);
      DataRow[] returnrow = ds.Tables[0].Select("DIP = '" + txt_Calc_BULK_DIP.Text + "' AND SLIDE = '" + txt_Calc_BULK_SLIDE.Text + "'");
      int result = returnrow.Length;
      DataRow dr = returnrow[0];

      txt_Calc_BULK_BULK.Text = (dr["BULK"].ToString());

      con.Close();
}