insert data to single table from multiple textboxes of form

private void btnSubmit_Click(object sender, EventArgs e)

{

   string result = "Please Enter ";

   if (txtBuyerName.Text == string.Empty)

   {

      result += "Buyer Name,";

   }

   if (txtBuyerAddress.Text == string.Empty)

   {

      result += "Buyer Address,";

   }

   if (txtBuyerRank.Text == string.Empty)

   {

      result += "Buyer Rank,";

      result = result.Remove(result.LastIndexOf(','));

   }

   else

   {

      if (result.Contains(','))

      {

         result = result.Remove(result.LastIndexOf(','));

      }

   }

   if (result != "Please Enter ")

   {

      MessageBox.Show(result);

   }

   else

   {

      string constr = "Server=servername;User Id=uid;Password=pwd;database=dbname";

      string query = "insert into buyer_choice values('" + txtBuyerName.Text + "','" +       txtBuyerAddress.Text + "','" + txtBuyerRank.Text + "')";

      SqlConnection con = new SqlConnection(constr);

      SqlCommand cmd = new SqlCommand(query, con);

      con.Open();

      if(cmd.ExecuteNonQuery()>0)

      {

         con.Close();

         txtBuyerName.Text = "";

         txtBuyerAddress.Text = "";

         txtBuyerRank.Text = "";

         MessageBox.Show("Record Inserted Successfully");

      }

   }

}