Dropdown list value not getting displayed in output

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            CityList.Items.Add("----Please Select----");
            CityList.Items.Add("Chennai");
            CityList.Items.Add("Madurai");
            CityList.Items.Add("Tirunelveli");
        }
    }
protected void btntxtbox_Click(object sender, EventArgs e)
    {
        lblresult.Text = string.Empty;

        string Name = nametxtbox.Text;
        string age = agetxtbox.Text;
        string email = emailtxtbox.Text;
        lblresult.Text = String.Format("Name = {0}, <br/> Age ={1}, <br /> Email = {2}, <br /> City ={3}",
            Name,
            age,
            email,
            CityList.SelectedItem.Text);
    }