Show city name in dropdownlist after selecting the country name.

 Database for fetching city name

 protected void Page_Load(object sender, EventArgs e)
    {
        drop2();
        drop();

    }

 public void drop2()
    {
        if (DropDownList4.SelectedItem.Text == "--Selectcountry--")
        {
            DropDownList5.Enabled = false;
            DropDownList5.SelectedValue = null;
        }
        else
            DropDownList5.Enabled = true;

    }

Autopost enabled in Dropdownlist of country 

 public void drop()
    {
        con.Open();
        string s = "select ward from country where cont='" + DropDownList4.SelectedValue.ToString() + "'";
        SqlCommand cmd = new SqlCommand(s, con);
        SqlDataReader dr = cmd.ExecuteReader();
        DropDownList5.DataSource = dr;
        DropDownList5.DataTextField = "city";
        DropDownList5.DataValueField = "city";
        DropDownList5.DataBind();
        con.Close();
    }