Q1. How to get a number is prime or NOT? public void prim() { int tmp, i; int num = Convert.ToInt16(ViewState["prim"].ToString()); for (i = 2; i < num; i++) { tmp = num % i; if (tmp == 0) { break; } } if (i == num) { lbl_prim.Text = "Number is prim"; } else { lbl_prim.Text = "Number is not prim"; } } On button event we get the values from text box--------- protected void btn_prim_Click(object sender, EventArgs e) { int num = Convert.ToInt16(txt_webname.Text); ViewState["prim"] = num; //prime_num(); prim(); }