DropDownList (Country-State-District-City)

How to Make a Complete Dropdown and Prevent Inserting Dummy Data from Form.

Disable other Controls when Clicked back to Parent Control:

Drop Down Sequence:

OnLoad
Load Country
On-Change
Load State according to Country
On-Change
Load Dists in State
On-Change
List Cities in Dist.


Code:

 protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
    {
        ddlState.DataSource = res.States(Convert.ToInt16(ddlCountry.SelectedValue));
        ddlState.DataTextField = "StateName";
        ddlState.DataValueField = "StateID";
        ddlState.DataBind();
        ddlState.Items.Insert(0, "Select");
        ddlDist.Enabled = false;
        ddlCity.Enabled = false;
    }
    protected void ddlState_SelectedIndexChanged(object sender, EventArgs e)
    {
        ddlDist.DataSource = res.Districts(Convert.ToInt16(ddlState.SelectedValue));
        ddlDist.DataTextField = "DistName";
        ddlDist.DataValueField = "DistID";
        ddlDist.DataBind();
        ddlDist.Items.Insert(0, "Select");
        ddlDist.Enabled = true;
        ddlCity.Enabled = false;
    }
    protected void ddlDist_SelectedIndexChanged(object sender, EventArgs e)
    {
        ddlCity.DataSource = res.Cities(Convert.ToInt16(ddlDist.SelectedValue));
        ddlCity.DataTextField = "CityName";
        ddlCity.DataValueField = "CityID";
        ddlCity.DataBind();
        ddlCity.Items.Insert(0, "Select");
        ddlCity.Enabled = true;
    }