Compare textbox value with database value

private void onShowClick(object sender, RoutedEventArgs e) {

           SqlConnection conn;
           SqlCommand cmdSelect;
           SqlDataReader reader;
           string connStr = ConfigurationManager.ConnectionStrings["house"].ConnectionString;
           conn = new SqlConnection(connStr);

           string select = "Select Date, Time, EndTime from Schedule";
           cmdSelect = new SqlCommand(select, conn);

           try {
               conn.Open();
               reader = cmdSelect.ExecuteReader();
               var valueDate = "";
               var valueStart = "";


               while(reader.Read()){

                   valueDate = reader["Date"].ToString();
                   valueStart = reader["Time"].ToString();

               }

               if (datePicker1.SelectedDate.ToString().Equals(valueDate) && timeText.Text.Equals(valueStart))
               {
                      MessageBox.Show("You have a same date and same time in your record(s). Please choose another date and/or time");
               }
               else {
                   MessageBox.Show("Your date and time is valid.");
               }
               conn.Close();
           }
           catch(Exception ex){
               MessageBox.Show(ex.Message);
           }


       }