Cascading three ComboBoxes

Question

My Windows form has three comboboxes. CmdCountry references a child table of CmdContinent, and CmdCity references a child table of CmdCountry.

But I get error like "wrong format" When I try to get ContinentId from cmbContinent_SelectedIndexChanged by coding.

int ContId = Convert.Into32(cmbContinent.SelectedValue.ToString());

My first two Comboboxes are like following:

private void Continent()
{
    var continent = (from u in db.Continent
                     select new { u.ContinentName,  u.ContinentId }
                    ).ToList();
    cmbContinent.DataSource = continent;
    cmbContinent.DisplayMember = "ContinentName";
    cmbContinent.ValueMember = "ContinentId";
}

private void cmbContinent_SelectedIndexChanged(object sender, EventArgs e)
{
    if (cmbContinent.SelectedValue.ToString() != null)
    { 
        int ContId = Convert.Into32(cmbContinent.SelectedValue.ToString()); // Here I get the error
        var country = (from u in db.Country
                       where u.ContinentId == ContId
                       select new { u.CountryId, u.CountryName }).ToList();

        cmbCountry.DataSource = country;
        cmbCountry.DisplayMember = "CountryName";
        cmbCountry.ValueMember = "CountryId";
    }
}

And loading first combobox Continent in Constructor:

public NewAccount()
{
    InitializeComponent(); 
    Continent();
}

I would be appreciated if anybody could help.

Answer 1

I use a ComboBox in my current project and I do something similar.

int valueMax = Convert.ToInt32(cbxNumberValues.SelectedItem);

For your code here is something that should work. Note that I've done little modification to be more conventionally coded.

int contId = Convert.ToInt32(cmbContinent.SelectedItem);

I would also suggest to use 'cbx' or 'cmb' and not 'cmd' as it tend to usually say command. But that's not very important