CODEWITHSUNDEEP
c#mysqlsqlsql-delete
Matteo
Matteo

Reputation: 346

Update and delete buttons C#

I wrote the code for the update button and the delete button. My purpose is update and delete the datas that I've inserted into the database (that was created in mysql with phpmyadmin).

Update button code:

void ModificaBtnClick(object sender, EventArgs e)
    {
        Connessione.Open();
        MySqlDataAdapter SDA=new MySqlDataAdapter("UPDATE INTO GARA set nome_gara='"+textBox1.Text+"',giudice='"+textBox2.Text+"',località='"+textBox3.Text+"',data='"+textBox4.Text+"',tpsopm='"+textBox5.Text+"',tpmopm='"+textBox6.Text+"',tpstot='"+textBox7+"',tpmtot='"+textBox8.Text+"')VALUES'"+textBox1.Text+"','"+textBox2.Text+"','"+textBox3.Text+"','"+textBox4.Text+"','"+textBox5.Text+"','"+textBox6.Text+"','"+textBox7.Text+"','"+textBox8.Text+"')",Connessione);
        SDA.SelectCommand.ExecuteNonQuery();
        Connessione.Close();

        MessageBox.Show("Dati modificati correttamente!");

    }

Delete button code:

void CancellaBtnClick(object sender, EventArgs e)
    {
        Connessione.Open();
        MySqlDataAdapter SDA=new MySqlDataAdapter("DELETE FROM GARA(nome_gara,giudice,località,data,tpsopm,tpmopm,tpstot,tpmtot)VALUES'"+textBox1.Text+"','"+textBox2.Text+"','"+textBox3.Text+"','"+textBox4.Text+"','"+textBox5.Text+"','"+textBox6.Text+"','"+textBox7.Text+"','"+textBox8.Text+"')",Connessione);
        SDA.SelectCommand.ExecuteNonQuery();
        Connessione.Close();
        MessageBox.Show("Dati cancellati correttamente!");
    }

I haven't syntax error, but when I run the program and I try to modify or delete the data, the compiler show me an unhandled exception (An Unhandled exception of type MySql.Data.MySqlClient.MySqlException was thrown). When I quit the window this line is selected SDA.SelectCommand.ExecuteNonQuery();

I use the same instruction for the insert button, but it works.

Can you help me, please?

Edit: I've tried your solutions, but the values don't update into the db. I can modify them into the dataGridView, but when I press the update button they don't change

Upvotes: 1

Views: 5338

Answers (2)

Thorsten Dittmar
Thorsten Dittmar

Reputation: 56697

I don't mean to sound harsh, but your code is not very good. Points to improve:

  1. Use correct SQL
  2. Stop using MySqlDataAdapter when you don't need to
  3. Use paramterized queries to avoid SQL injections (and no: there's no excuse whatsoever for not doing this!)

These three points will lead to the following code:

void ModificaBtnClick(object sender, EventArgs e)
{
    Connessione.Open();
    MySqlCommand cmd = new MySqlCommand("UPDATE GARA set nome_gara=@nomegara,giudice=@giudice,località=@localita,data=@data ...",Connessione);

    cmd.Parameters.AddWithValue("@nomegara", textBox1.Text);
    cmd.Parameters.AddWithValue("@giudice", textBox2.Text);
    ...

    cmd.ExecuteNonQuery();

    MessageBox.Show("Dati modificati correttamente!");
}

void CancellaBtnClick(object sender, EventArgs e)
{
    Connessione.Open();
    MySqlCommand cmd =new MySqlCommand("DELETE FROM GARA WHERE Field = @value, ...",Connessione);

    cmd.Parameters.AddWithValue("@value", ...);
    ...

    cmd.ExecuteNonQuery();
    MessageBox.Show("Dati cancellati correttamente!");
}

Upvotes: 2

ScaisEdge
ScaisEdge

Reputation: 133370

Update don't need INTO but only 

UPDATE   GARA 
 SET set nome_gara='"+textBox1.Text+"'
,giudice='"+textBox2.Text+"'
,località='"+textBox3.Text+"'
,.....

eventulally add where condition for update the rows you need

Delete don't need value you delete the rows with match where condition eg:

DELETE FROM GARA
WHERE nome_gara='"+textBox1.Text+"'"

be sure for the proper where condition

and be careful in string concat that you are at risk for sql injections

Upvotes: 2

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