i have to retrieve the value from sqlserver

Question

i have to retrieve the value from sqlserver 2008.

my design is

<table align="center" style="border-color: #1d599e; border-style: outset;border-width: thin; background-color:  #D7D7D7; width:50%">

<tr style="margin-left: 80px; background:#1d599e;" align="center"  colspan="2">

<td class="style2" style="margin-left: 80px; background:#1d599e;" align="center">

Billing Details

</td>

</tr>

<tr>

<td class="style2">

    <asp:Label ID="Label1" runat="server" Text="Product"></asp:Label>

</td>

<td>

    <asp:DropDownList ID="DropDownList3" runat="server" Height="16px" Width="132px" 

        AppendDataBoundItems="True" AutoPostBack="True" 

        onselectedindexchanged="DropDownList3_SelectedIndexChanged">

        <asp:ListItem>--Select Product--</asp:ListItem>

    </asp:DropDownList>

</td>

</tr>

<tr>

<td class="style2">

    <asp:Label ID="Label2" runat="server" Text="BillNo"></asp:Label>

</td>

<td>

    <asp:TextBox ID="txtbillno" runat="server"></asp:TextBox>

    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" 

        onrowdatabound="GridView1_RowDataBound" Width="100px">

    <Columns>

    <asp:TemplateField HeaderText="Choose">

    <ItemTemplate>

        <asp:CheckBox ID="CheckBox1" runat="server" />

        </ItemTemplate>

    </asp:TemplateField>  

    <asp:BoundField  HeaderText="ItemName" DataField="brandname" Visible="false"/> 

    <asp:TemplateField HeaderText="ItemName">

    <ItemTemplate>

        <asp:TextBox ID="itname" runat="server" Text='<%#Bind("brandname")%>'></asp:TextBox>

        

    </ItemTemplate>

    </asp:TemplateField> 

    

 

    <asp:TemplateField HeaderText="Quantity">

      <ItemTemplate>

          <asp:DropDownList ID="ddlw" runat="server" AutoPostBack="True" 

              onselectedindexchanged="ddlw_SelectedIndexChanged">

          </asp:DropDownList>

         

         

            </ItemTemplate>

    </asp:TemplateField>

      <asp:TemplateField HeaderText="RequiredNo">

    <ItemTemplate>

        <asp:DropDownList ID="DropDownList1" runat="server" 

            onselectedindexchanged="DropDownList1_SelectedIndexChanged" 

            AutoPostBack="True">

                        <asp:ListItem Value="0">Choose</asp:ListItem>

                        <asp:ListItem>1</asp:ListItem>

                        <asp:ListItem>2</asp:ListItem>

                        <asp:ListItem>3</asp:ListItem>

                        <asp:ListItem>4</asp:ListItem>

                        <asp:ListItem>5</asp:ListItem>

                        <asp:ListItem>6</asp:ListItem>

                        <asp:ListItem>7</asp:ListItem>

                        <asp:ListItem>8</asp:ListItem>

                        <asp:ListItem>9</asp:ListItem>

                        <asp:ListItem>10</asp:ListItem>

                      

        </asp:DropDownList>

    </ItemTemplate>

    </asp:TemplateField>

      <asp:TemplateField HeaderText="Cost">

    <ItemTemplate>

        <asp:TextBox ID="pprc" runat="server"  ></asp:TextBox>

    </ItemTemplate>

    </asp:TemplateField>

    

    <asp:TemplateField HeaderText="beforevat">

    <ItemTemplate>

        <asp:TextBox ID="bfvata" runat="server" ontextchanged="bfvata_TextChanged"></asp:TextBox>

        </ItemTemplate>

        </asp:TemplateField>

    

    <asp:TemplateField HeaderText="Extra">

    <ItemTemplate>

        <asp:TextBox ID="txextra" runat="server" ontextchanged="txextra_TextChanged" AutoPostBack="true"

        ></asp:TextBox>

        </ItemTemplate>

    </asp:TemplateField>

    

    <asp:TemplateField HeaderText="CorrectPrice">

    <ItemTemplate>

        <asp:TextBox ID="txtcc" runat="server" ontextchanged="txtcc_TextChanged" AutoPostBack="true"></asp:TextBox>    

    </ItemTemplate>

    </asp:TemplateField>

    

    <asp:TemplateField HeaderText="ActualPrice">

    <ItemTemplate>

        <asp:TextBox ID="txtactl" runat="server"></asp:TextBox>    

    </ItemTemplate>

    </asp:TemplateField>

    

    <asp:TemplateField HeaderText="VAT">

    <ItemTemplate>

        <asp:TextBox ID="txvat" runat="server"></asp:TextBox>

    </ItemTemplate>

    </asp:TemplateField>

    

    <asp:TemplateField HeaderText="TotalAmount">

    <ItemTemplate>

        <asp:TextBox ID="txtamt" runat="server"></asp:TextBox>    

    </ItemTemplate>

    </asp:TemplateField>

    

    

    </Columns>

    </asp:GridView>

</td>

</tr>

<tr>

<td colspan="2">

    &nbsp;</td>

<td>

</td>

</tr>

</table>

mycode is

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_AddmoreProduct : System.Web.UI.Page

{

    SqlConnection con = new SqlConnection("Data Source=VALUED-HO1E64NO\\SQLEXPRESS;Initial Catalog=Agri;User ID=sa;Password=watt");

    DataSet ds = new DataSet();

    REMO sel = new REMO();

    protected void Page_Load(object sender, EventArgs e)

    {

        if (!IsPostBack)

        {

          

        }

        sno();

        sg();

    }

    private void sno()

    {

        string bill = sel.getmaxid("BillNo", "cement1");

        txtbillno.Text = bill.ToString();

    }

    void LoadData()

    {

        SqlConnection con = new SqlConnection("Data Source=VALUED-HO1E64NO\\SQLEXPRESS;Initial Catalog=Agri;User ID=sa;Password=watt");

        SqlDataAdapter cmd = new SqlDataAdapter("select distinct brandname from demo1 where productname='"+DropDownList3.SelectedItem.Text+"'", con);

        DataSet ds=new DataSet();

        cmd.Fill(ds);

        GridView1.DataSource = ds.Tables[0];

        GridView1.DataBind();

       

    }

    private void sg()

    {

        ListItem sll = new ListItem();

        DropDownList3.Items.Add("Cement");

        DropDownList3.Items.Add("Seed");

        DropDownList3.Items.Add("Pesticide");

        DropDownList3.Items.Add("Fetilizer");

        DropDownList3.Items.Add(sll.ToString());

    }

    protected void txtbillno_TextChanged(object sender, EventArgs e)

    {

       // DataTable dt;

        //dt="select 

    }

    // private void prr()

    //{

    //    int s = 0;

    //     DataSet ds=new DataSet();

    //    ListItem lim = new ListItem();

    //    //lim.Text = "Select";

    //    //lim.Value = "0";

    //    //DropDownList1.Items.Add(lim.ToString());

    //    ds = sel.GETDS("select DISTINCT name from demo");

    //    //DropDownList1.Items.Insert(0, new ListItem("--Select--", "0"));

    //    foreach (DataRow dr in ds.Tables[0].Rows)

    //    {

    //       // DropDownList1.Items.Clear();

    //        ListItem ss = new ListItem();

    //        lim.Text = dr["name"].ToString();

    //        lim.Value = Convert.ToString(s + 1);

    //        DropDownList1.Items.Add(lim.ToString());

    //    }

    //}

    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)

    {

        if (e.Row.RowType == DataControlRowType.DataRow)

        {

            con.Open();

            var ddl = (DropDownList)e.Row.FindControl("ddlw");

            var name=Convert.ToString(((TextBox)e.Row.FindControl("itname")).Text);

            //int CountryId = Convert.ToInt32(e.Row.Cells[0].Text);

            SqlCommand cmd = new SqlCommand("select distinct weight from demo1 where brandname='"+name+"'", con);

            SqlDataAdapter da = new SqlDataAdapter(cmd);

            DataSet ds = new DataSet();

            da.Fill(ds);

            con.Close();

            ddl.DataSource = ds;

            ddl.DataTextField = "weight";

            ddl.DataValueField = "weight";

            //ddl.DataValueField = "StateID";

            ddl.DataBind();

            ddl.Items.Insert(0, new ListItem("--Select--", "0"));

            // float sllv = Convert.ToSingle((TextBox)GridView1.FindControl("pprice"));

            //float scv = Convert.ToSingle((DropDownList)GridView1.FindControl("DropDownList1"));

            // TextBox sllv = e.Row.FindControl("pprce") as TextBox;

            //  DropDownList scv = e.Row.FindControl("DropDownList1") as DropDownList;

           

        }

    }

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

    {

        foreach (GridViewRow gvrow in GridView1.Rows)

        {

            float sllv = Convert.ToInt32(((TextBox)gvrow.FindControl("pprce")).Text);

            float scv = Convert.ToInt32(((DropDownList)gvrow.FindControl("DropDownList1")).SelectedValue);

            ((TextBox)gvrow.FindControl("bfvata")).Text = Convert.ToString(sllv * scv);

           string kishh=((TextBox)gvrow.FindControl("bfvata")).Text;

           ((TextBox)gvrow.FindControl("txtcc")).Text = Convert.ToString(int.Parse(kishh) * (14.5 / 100));

           string kishore = ((TextBox)gvrow.FindControl("txtcc")).Text;

           // ((TextBox)e.Row.FindControl("bfvata")).Text = Convert.ToString(sllv * scv);

        }

    }

    protected void txextra_TextChanged(object sender, EventArgs e)

    {

        foreach (GridViewRow gvrow in GridView1.Rows)

        {

            float ses, sddd, pry;

            string cs = ((TextBox)gvrow.FindControl("txtcc")).Text;

           string hds = ((TextBox)gvrow.FindControl("bfvata")).Text;

           string kish = ((TextBox)gvrow.FindControl("txtactl")).Text;

           ses = float.Parse(cs);

           sddd = float.Parse(hds);

           //pry = float.Parse(kish);

          

           //pry = float.Parse(kish);

           pry = (ses + sddd);

           ((TextBox)gvrow.FindControl("txtactl")).Text = pry.ToString();

          //  string amam = ((TextBox)gvrow.FindControl("txtactl")).Text;

            

        }

        //foreach (GridViewRow gvrow in GridView1.Rows)

        //{

        //    float gun = Convert.ToInt32(((TextBox)gvrow.FindControl("bfvata")).Text);

        //    float gs = Convert.ToInt32(((TextBox)gvrow.FindControl("txextra")).Text);

        //    ((TextBox)gvrow.FindControl("txtcc")).Text = Convert.ToString(gun + gs);

        //}

        //txtcc

    }

    protected void bfvata_TextChanged(object sender, EventArgs e)

    {

        

    }

    protected void txtcc_TextChanged(object sender, EventArgs e)

    {

       

    }

    protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)

    {

        LoadData();

    }

    protected void ddlw_SelectedIndexChanged(object sender, EventArgs e)

    {

        

        foreach (GridViewRow gvrow in GridView1.Rows)

        {

       

            var wegt = ((DropDownList)gvrow.FindControl("ddlw")).Text;

        

            SqlCommand cmd = new SqlCommand("select price from demo1 where weight='" + wegt + "'",con);

            SqlDataAdapter da = new SqlDataAdapter(cmd);

            DataSet ds = new DataSet();

            da.Fill(ds);

            GridView1.DataSource = ds.Tables["price"];

            GridView1.DataBind();

                  

    

}

i need if i choose the quantity as 25 i need the price for that particular quantity. but the data set is empty