How to add items in ComboBox from database

Question

Im trying to add items in the comboBox (cmbInstructor) namely the last names (instructorLN) however, my code does not seem to work. Any ideas on where I went wrong?

private void cmbInstructor_SelectedIndexChanged(object sender, EventArgs e)
{
    MySqlConnection conn = new MySqlConnection(mycon);
    MySqlCommand cmd = new MySqlCommand("SELECT * FROM instructor WHERE instructorType ='" + labelClass.Text + "'", conn);
    string instructorLN = "";

    conn.Open();
    MySqlDataReader myReader = null;
    myReader = cmd.ExecuteReader();

    while (myReader.Read())
    {
        instructorLN = myReader["instructorLN"].ToString();
    }
    cmbInstructor.Items.Add(instructorLN);
}

Soner Gönül · Accepted Answer · 2015-08-14 14:17:28Z

1

As far as I can see, you are adding only last value that your SELECT returns.

Move your

cmbInstructor.Items.Add(instructorLN);

line into to the while statement as;

while (myReader.Read())
{
    cmbInstructor.Items.Add(myReader["instructorLN"].ToString());
}

By the way, you should always use parameterized queries. This kind of string concatenations are open for SQL Injection attacks.

Also use using statement to dispose your connection and command and reader automatically.

using(var conn = new MySqlConnection(mycon))
using(var cmd = conn.CreateCommand())
{
    cmd.CommandText = "SELECT * FROM instructor WHERE instructorType = @type";
    cmd.Parameters.Add("@type", labelClass.Text);

    conn.Open();
    using(var myReader = cmd.ExecuteReader())
    {
        while (myReader.Read())
        {
             cmbInstructor.Items.Add(myReader["instructorLN"].ToString());
        }
    }
}

edited Aug 14, 2015 at 14:17

answered Aug 14, 2015 at 14:11

Soner Gönül

99.1k103 gold badges224 silver badges375 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

square_fish Over a year ago

Thank you for the help...but it seems that the items still wont show

Soner Gönül Over a year ago

@jgf Why you using this code in SelectedIndexChanged event of your combobox? Did you debug your code and see what's going on?

Collectives™ on Stack Overflow

How to add items in ComboBox from database

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related