Executing a SQL query with C#

Question

I would like to add some information to my database. I searched for some tutorials, but none of them work.

NonQuery can do what he needs to do, because the messagebox returns "Success" (1). But it does not update my database. If I put the same query to "Add New Query", directly to my database, it works.

Can someone help me?

My class code at the moment:

namespace BurnThatFat
{
    class databaseconnection
    {
        //fields
        SqlConnection connection;
        string connectionstring;

        public databaseconnection()
        {
            // fields waarde toewijzen
            connectionstring = @"Data Source=(LocalDB)\MSSQLLocalDB;" +
                @"AttachDbFilename=|DataDirectory|\Database2.mdf;Integrated Security=True";
            connection = new SqlConnection(connectionstring);
            OpenConnection();
            CloseConnection();
        }

        public List<Object> getObjectsFromDatabase()
        {
            try
            {
                OpenConnection();
                // sql query
                // Datareader
                // sqlcommand
                // return list van objecten , objecten veranderd naar jouw wens van data.
                CloseConnection();
            }
            catch (Exception)
            {
                throw;
            }
            return new List<object>();
        }

        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;
            }
        }

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

        public void AddGebruiker()
        {
            string query = "insert into Gebruiker VALUES(3, 'Cihan', 'Kurt', 18, 'Man', 85, 75, 'Admin1', 'Test123', 'testen');";
            using (connection)
            {
                SqlCommand command = new SqlCommand(query, connection);
                OpenConnection();
                int resultaat = command.ExecuteNonQuery();
                if (resultaat == 1)
                {
                    MessageBox.Show("succes");
                }
                else
                {
                    MessageBox.Show("fail");
                }
            }
        }
    }
}

Edit:

And this is the code for my buttons etc:

   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;

// voor sql connectie.
using System.Data.SqlClient;



namespace BurnThatFat
{
    public partial class SignUp : Form
    {

        databaseconnection db = new databaseconnection();

        public SignUp()
        {
            InitializeComponent();
            gb_login.Visible = false;
            gb_Voornaam.Visible = false;
            gb_Achternaam.Visible = false;
            gb_leeftijdgeslacht.Visible = false;
            gb_gewicht.Visible = false;
            gb_email.Visible = false;
            gb_Start.Visible = true;


        }


        private void btn_SignUp_Click(object sender, EventArgs e)
        {
            gb_Start.Visible = false;
            gb_Voornaam.Visible = true;
        }

        private void btn_login_Click(object sender, EventArgs e)
        {
            gb_Start.Visible = false;
            gb_login.Visible = true;
        }

        private void btn_loginvolgende_Click(object sender, EventArgs e)
        {
            gb_login.Visible = false;
            // hier moet nog een GB!!!!!!
        }

        private void btn_voornaamvolgende_Click(object sender, EventArgs e)
        {


            gb_Voornaam.Visible = false;
            gb_Achternaam.Visible = true;
        }

        private void btn_achternaamvolgende_Click(object sender, EventArgs e)
        {
            gb_Achternaam.Visible = false;
            gb_leeftijdgeslacht.Visible = true;
        }

        private void btn_leeftijdvolgende_Click(object sender, EventArgs e)
        {
            gb_leeftijdgeslacht.Visible = false;
            gb_gewicht.Visible = true;
        }


        // einde registratie
        // opslaan van gegevens in database
        private void btn_emailvolgende_Click(object sender, EventArgs e)
        {
            // gebruiker = new Gebruikerklasse();
           // gebruiker.Naam = Convert.ToString(tb_voornaam.Text);
           //// gebruiker.Achternaam = Convert.ToString(tb_achternaam.Text);
          //  gebruiker.Leeftijd = Convert.ToInt32(nud_leeftijd.Value);
          ///  gebruiker.Geslacht = Convert.ToString(cb_geslacht.Text);
          //  gebruiker.Huidig_gewicht = Convert.ToInt32(nud_huidiggewicht.Value);
          //  gebruiker.Streef_gewicht = Convert.ToInt32(nud_streefgewicht.Value);
          ///  gebruiker.Gebruikersnaam = Convert.ToString(tb_gebruikersnaam2.Text);
          //  gebruiker.Email = Convert.ToString(tb_email.Text);
         //   gebruiker.Wachtwoord = Convert.ToString(tb_wachtwoordsignup.Text);

            db.AddGebruiker();
            gb_email.Visible = false;
            // hier moet nog een GB!!!!!

        }

        private void btn_gewichtvolgende_Click(object sender, EventArgs e)
        {
            gb_gewicht.Visible = false;
            gb_email.Visible = true;
        }
    }
}    

Answer 1

The simplest way to insert into a SQL Server database:

string connectionString = @"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Database2.mdf;Integrated Security=True";

string commandText = "INSERT INTO MyTable (ID, Name, Address) VALUES (10, 'Bob', '123 Main Street');";

using (SqlConnection conn = new SqlConnection(connectionString))
using (SqlCommand cmd = new SqlCommand(commandText, conn))
{
    conn.Open();
    cmd.ExecuteNonQuery();
    conn.Close();
}

As long as commandText is a working query, it should insert a row. It would be better to use parameters for your values instead of hard coding them like I did here - that avoids SQL injection attacks and other potential problems. You can search Google for that (or the question you are asking now) and find tons of resources to help you.

If you need more specific help, post details such as what is actually happening when you try to run your code - are you getting an exception?

Answer 2

I'd clean up a bunch of things before doing anything else.

First, get rid of the openconnection and closeconnection methods all together. And don't keep an instance property for the connection in your class. Create the connection ondemand with a using statement, because at the end of the using statement the compiler will insert a call to the Dispose method on the connection's IDisposable interface implementation and it will close the connection automatically for you.

So after cleaning up all the unnecessary code all you really should have in this class is an implementation of your Addgebrukier method which would look like this

public void AddGebruiker()
{
        string query = "insert into Gebruiker VALUES(3, 'Cihan', 'Kurt', 18, 'Man', 85, 75, 'Admin1', 'Test123', 'testen');";
        using (SqlConnection = new SqlConnection(connectionstring))
        {
            using (SqlCommand command = new SqlCommand(query, connection))
            {
                connection.Open();
                int resultaat = command.ExecuteNonQuery();
                if (resultaat == 1)
                {
                    MessageBox.Show("succes");
                }
                else
                {
                    MessageBox.Show("fail");
                }
            }
        }
    }

You should also load your connection string from the section in the app/web.config, but you can do that later after you get it running.

Answer 3

Here is a simple concept that should work perfectly fine for you. Just change the ServerName, DatabaseName, etc.

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            SqlConnection connection ;
            SqlDataAdapter adapter = new SqlDataAdapter();
            string sql = null;
            connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
            connection = new SqlConnection(connetionString);
            sql = "insert into product (Product_id,Product_name,Product_price) values(6,'Product6',600)";
            try
            {
                connection.Open();
                adapter.InsertCommand = new SqlCommand(sql, connection);
                adapter.InsertCommand.ExecuteNonQuery();
                MessageBox.Show ("Row inserted !! ");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }
    }
}