How to debug my country>states>cities code so it displays states and cities?

Question

private void Form2_Load(object sender, EventArgs e)
{
    var countries = from country in xdoc.Descendants("countries").Elements("country").Attributes("name")
                    select country.Value;
    comboBox_country.DataSource = countries.ToList()
}

private void comboBox_country_SelectedIndexChanged(object sender, EventArgs e)
{
    var states = from country in xdoc.Descendants("countries").Elements("country")
                 where country.Attribute("name").Value == comboBox_country.SelectedValue
                 select country;

    var s = from state in states.Elements("state")
            select state.Value;
    comboBox_state.DataSource = s.ToList();
}

private void comboBox_state_SelectedIndexChanged(object sender, EventArgs e)
{
    var cities = from state in xdoc.Descendants("state").Elements("state")
                 where state.Attribute("name").Value == comboBox_state.SelectedValue
                 select state;

    var c = from city in cities.Elements("city")
            select city.Value;
           comboBox_city.DataSource = c.ToList();
}

Where do I need to do modifications?

I am trying to select countries related to states and related cities. I've created an XML file and trying to read from that XML file into a win form layout which has countries state city as labels and corresponding combo boxes.