Filter on combobox based on another combobox with same table data in c#

Question

I have 2 combo boxes and data grid view I can filter 2 combo boxes separately base on the table but I want to filter them based on 1st combo box. I tried different ways but my second combo box is empty.. nothing happens.. please help me with this.

{
    String Query = " SELECT  distinct [t_street_name] FROM  [ICPS].[dbo].[tickets]  ";
    SqlConnection conDataBase = new SqlConnection(conString);
    SqlCommand cmdDataBase = new SqlCommand(Query, conDataBase);
    SqlDataAdapter sda = new SqlDataAdapter(cmdDataBase);
    SqlDataReader myReader;
    try
    {
        conDataBase.Open();
        myReader = cmdDataBase.ExecuteReader();

        while (myReader.Read())
        {
            string t_street_name = myReader["t_street_name"].ToString();
            comboBox1.Items.Add(t_street_name);
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

void fillcombo1()
{

    String Query =  ("SELECT  distinct [t_zone_name] FROM  [ICPS].[dbo].[tickets] where  [t_street_name] ='" + comboBox1.SelectedItem + "'conString ") ;
    SqlConnection conDataBase = new SqlConnection(conString);
    SqlCommand cmdDataBase = new SqlCommand(Query, conDataBase);
    SqlDataReader myReader;
    try
    {
        conDataBase.Open();
        myReader = cmdDataBase.ExecuteReader();

        while (myReader.Read())
        {
            string t_zone_name = myReader["t_zone_name"].ToString();
            comboBox2.Items.Add(t_zone_name);
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

private void Form1_Load(object sender, EventArgs e)
{
}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
}

private void button2_Click(object sender, EventArgs e)
{
    SqlConnection conDatabase = new SqlConnection(constring);

    conDatabase.Open();

    DataTable db = new DataTable();
    SqlDataAdapter sda = new SqlDataAdapter(String.Format("select  distinct *  from" + " [ICPS].[dbo].[tickets] " +
    "where   [ICPS].[dbo].[tickets].[t_street_name]  = '" + comboBox1.Text + "'" +
    "and ([ICPS].[dbo].[tickets].[t_date_time_issued]) BETWEEN Convert(DATETIME, '{0}', 103) AND Convert(DATETIME, '{1}', 103)", StartDate.Value.ToString("dd/MM/yyyy"), EndDate.Value.ToString("dd/MM/yyyy")), constring);

    sda.Fill(db);

    dataGridView1.DataSource = db;
}

Answer 1

You're looking for filtering like state/city (as an example), correct? So if someone picks a state in the first combo box, then you want a list of cities within that state to populate in the second combo box. Correct?

Answer 2

Apart from the obvious comments about using parametrized queries and Using the SQL connection, have you actually checked the SQL statement directly in a database management program? To me it looks like there is no space in the statement text between

... comboBox1.Text + "'" + "and ([ICPS].[dbo] ...

Apart from that you obviously need to load the second combo from the selected index event on the first combo.

Answer 3

I have tried it everything work fine now..

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e) {

         SqlConnection conDatabase = new SqlConnection(constring);

        comboBox2.SelectedIndex = -1;
        comboBox2.Items.Clear();
        if ( conDatabase.State == ConnectionState.Closed)
        {
            conDatabase.Open();
        }
        SqlCommand cmd = new SqlCommand(" select distinct  sz_zone_name from  [ICPS].[dbo].[spid_zones] " + 
            "inner join [ICPS].[dbo].[spid_street]" +
             " on [ICPS].[dbo].[spid_street].ss_number = [ICPS].[dbo].[spid_zones].[sz_street_number]"  +
         " where [ICPS].[dbo].[spid_street].ss_name  ='" + comboBox1.SelectedItem + "'", conDatabase);
        SqlDataReader rd = cmd.ExecuteReader();
        while (rd.Read())
        {
            comboBox2.Items.Add(rd[0]);
        }