C# execute SQL query and return or show response

Question

I'm trying to run a SELECT query in my C# application, but im literally stuck actually. How would I select something from a MySql database?

My current code looks like the following:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MySql.Data.MySqlClient;

namespace Helpful
{
    class database_connector
    {
        private MySqlConnection connection;
        private string server;
        private string database;
        private string uid;
        private string password;

        // Constructor
        public database_connector()
        {
            Initialize();
        }

        //Initialize values
        private void Initialize()
        {
            server = "xxx";
            database = "xxx";
            uid = "xxx";
            password = "xxx";
            string connectionString;
            connectionString = "SERVER=" + server + ";" + "DATABASE=" +
            database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";

            connection = new MySqlConnection(connectionString);
        }

        //open connection to database
        private bool OpenConnection()
        {
            try
            {
                connection.Open();
                return true;
            }
            catch (MySqlException ex)
            {
                switch (ex.Number)
                {
                    case 0:
                        MessageBox.Show("Cannot connect to server. Contact administrator.");
                        break;
                    case 1045:
                        MessageBox.Show("Invalid username/password, please try again");
                        break;
                }
                return false;
            }
        }

        //Close connection
        private bool CloseConnection()
        {
            try
            {
                connection.Close();
                return true;
            }
            catch (MySqlException ex)
            {
                MessageBox.Show(ex.Message);
                return false;
            }
        }

        //Select statement
        public void user_check(string username, string password)
        {
            string query = "SELECT * FROM swear_tool WHERE username =" + username;

            if (this.OpenConnection() == true)
            {
                MySqlCommand cmd = new MySqlCommand(query, connection);
                MySqlDataReader dataReader = cmd.ExecuteReader();
                dataReader.Close();
                this.CloseConnection();
            }
        }
    }
}

But how could I see if this actually worked? Because if I try to show the result in a messagebox it would return, could not be translated to a string.

if (this.OpenConnection() == true)
{
    MySqlCommand cmd = new MySqlCommand(query, connection);
    MySqlDataReader dataReader = cmd.ExecuteReader();
    MessageBox.Show(dataReader);
    dataReader.Close();
    this.CloseConnection();
}

Yeah, you cannot do it like that. This should get you going in the right direction: msdn.microsoft.com/en-us/library/haa3afyz(v=vs.110).aspx — sgeddes
– sgeddes, Commented Aug 1, 2016 at 19:00

Rafael Passarela · Accepted Answer · 2016-08-01 19:10:01Z

1

You need to know what field you want from database. Use a SQL like this SELECT Id, Name FROM swear_tool WHERE username =" + username and the code for retrieve the Name field.
Index 0 = Id
Index 1 = Name <-- GetString(1)

if (dataReader.HasRows) {
    while (dataReader.Read()) {
        Console.WriteLine("{0}", dataReader.GetString(1) );
    }
} else {
    Console.WriteLine("No rows.");
}

answered Aug 1, 2016 at 19:10

Rafael Passarela

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