input string was in correct format

in my .net app i add guest parameters are guest_id,first_name,email_address,phone_number

i also create a procedures of addguest and view then when i debug the error is shows is input string is not in corret format in 2nd line

 public partial class WebForm4 : System.Web.UI.Page
    {

        ClassLibrary1.Class1 aa = new ClassLibrary1.Class1();

        
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void MyButton_Click(object sender, EventArgs e)
        {
            if(aa.addguest(Convert.ToInt32(id_txt.Text),txt_name.Text,txt_address.Text,Convert.ToInt32(num_txt.Text))==true)
            {
                GridView1.DataSource=aa.show();
            }
            GridView1.DataSource=aa.show();
            GridView1.DataBind();


        }

and classlibrary work is

public class Class1
    {
        public bool addguest(int guest_id, string first_name, string Email_address, int Phone_number)
        {
            try
            {
                Database db = DatabaseFactory.CreateDatabase("sed");
                db.ExecuteDataSet("addguest", new object[] { guest_id, first_name, Email_address, Phone_number });
                return true;
            }
            catch
            {
                return false;
            }
        }
        public DataTable show()
        {
            Database db = DatabaseFactory.CreateDatabase("sed");
           return db.ExecuteDataSet("view").Tables[0];
        }

how i solve this