how to multiply textbox value and dropdown value asp.net

from dropdown value and textbox value need to multiply now

it sum the dropdown and text box not multiply.Hussain

ya thanks .how to multiply.. without use button click event

have to multiply dropdown3 and textbox3

using System; using System.Collections; using System.Configuration; using System.Data; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.HtmlControls; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Xml.Linq; using System.Data.SqlClient; public partial class Admin_Default : System.Web.UI.Page { REMO sel = new REMO(); DataSet ds = new DataSet(); string s = ConfigurationManager.AppSettings["RM"].ToString(); SqlConnection cn = new SqlConnection(); SqlCommand cd = new SqlCommand(); SqlDataAdapter da = new SqlDataAdapter(); protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { prr(); sno(); pqice(); txtdate.Text = System.DateTime.Now.ToShortDateString(); } } private void sno() { // int z = 0; //ListItem cb = new ListItem(); // ds = sel.GETDS("select Billno from numbeer"); ds = sel.GETDS("select min (Billno) as Billno from numbeer where status='view'"); foreach (DataRow dr in ds.Tables[0].Rows) { //ListItem sw = new ListItem(); txtbillno.Text = dr["Billno"].ToString(); //sw.Value = Convert.ToString(z + 1); } } private void pqice() { ListItem lik = new ListItem(); lik.Text = "Select"; lik.Value = "0"; for (int se = 300; se <= 700; se++) { DropDownList3.Items.Add(Convert.ToString(se)); } } private void prr() { int s = 0; ListItem lim = new ListItem(); lim.Text = "Select"; //lim.Value = "0"; DropDownList1.Items.Add(lim.ToString()); ds = sel.GETDS("select DISTINCT name from demo"); foreach (DataRow dr in ds.Tables[0].Rows) { ListItem ss = new ListItem(); lim.Text = dr["name"].ToString(); lim.Value = Convert.ToString(s + 1); DropDownList1.Items.Add(lim.ToString()); } } protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) { DropDownList2.Items.Clear(); DataSet ds = new DataSet(); string qr = "select weight from demo where name='" + DropDownList1.SelectedValue.ToString() + "'"; ds = sel.GETDS(qr); ListItem se = new ListItem(); se.Value = "0"; se.Text = "Select"; foreach (DataRow dr in ds.Tables[0].Rows) { ListItem liz = new ListItem(); //liz.Text = "Select"; liz.Value = dr["weight"].ToString(); DropDownList2.Items.Add(liz.ToString()); } } protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e) { ListItem sss = new ListItem(); sss.Text = "Select"; DataSet ds = new DataSet(); string sq = "select price from demo where weight='" + DropDownList2.SelectedItem.ToString() + "'"; ds = sel.GETDS(sq); TextBox1.Text = ds.Tables[0].Rows[0]["price"].ToString(); foreach (DataRow dr in ds.Tables[0].Rows) { TextBox1.Text = dr["price"].ToString(); } } protected void Button1_Click(object sender, EventArgs e) { //string qrt = "insert into cement (Date,BillNo,CustomerName,Address,ProductName,Quantity,Price,Extra) values ('" + txtdate.Text; //qrt += "','" + txtbillno.Text; //qrt += "','" + txtcn.Text; //qrt += "','" + txtad.Text; //qrt += "','" + DropDownList1.SelectedItem.ToString(); //qrt += "','" + DropDownList2.SelectedItem.ToString(); //qrt += "','" + TextBox1.Text; //// qrt += "','" + ddprice.SelectedItem.ToString(); //qrt += "','" + txtex.Text; //qrt += "')"; //sel.Insert(qrt); //Label10.Visible = true; //Label10.Text = "Sucess"; //cn = new SqlConnection(s); //cn.Open(); //string qrs = "insert into product (date,Product,BillNo,ProductName,Quantity,Price,Extra) values ('" + txtdate.Text; //qrs += "','" + TextBox2.Text; //qrs += "','" + txtbillno.Text; ////sqrs += "','" + txtcn.Text; //qrs += "','" + DropDownList1.SelectedItem.ToString(); //qrs += "','" + DropDownList2.SelectedItem.ToString(); //qrs += "','" + TextBox1.Text; ////qrs += "','" + ddprice.SelectedItem.ToString(); //qrs += "','" + txtex.Text; //qrs += "')"; ////sel.Insert(qrs); //cd = new SqlCommand(qrs, cn); //cd.ExecuteNonQuery(); //cn.Close(); string up = "update numbeer set status='Viewed' where Billno='" + txtbillno.Text + "'"; sel.Insert(up); } protected void Button2_Click(object sender, EventArgs e) { txtbillno.Text = ""; txtcn.Text = ""; txtad.Text = ""; DropDownList1.SelectedValue = "Select"; //DropDownList2.SelectedValue = "Select"; TextBox1.Text = ""; txtex.Text = ""; } //protected void txtbillno_TextChanged(object sender, EventArgs e) //{ // string up = "update numbeer set status='Viewed' where Billno='" + txtbillno.Text + "'"; // sel.Insert(up); //} //protected void txtcn_TextChanged(object sender, EventArgs e) //{ // string up = "update numbeer set status='Viewed' where Billno='" + txtbillno.Text + "'"; // sel.Insert(up); //} protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e) { txttp.Text ="sum:"+(Convert.ToInt32(DropDownList3.SelectedValue) + Convert.ToInt32(TextBox1.Text)); } }

its not working