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;
    }
John Bhatt
Glad to Know, Free to Share.....
http://www.johnbhatt.com