How to multiply textbox with gridview columns

I have write this code to create a gridview with 3 columns

DataTable dt = new DataTable();
dt = new DataTable();
dt.Columns.Add("ID", typeof(int)).AutoIncrement = true;
dt.Columns.Add("Name"开发者_StackOverflow中文版, typeof(string));
dt.Columns.Add("Price(Grouch)/Hectares", typeof(float));
DataColumn[] keys = new DataColumn[2];
keys[0] = dt.Columns["ID"];
dt.PrimaryKey = keys;
dt.Rows.Add("1", "Seaside Location", 1.5);

Session[key] = dt;
return dt;

I would like to add in this code a textbox with the quantity.

When i give the quantity i want in another textbox to have the total.

for example 2*1.5=3

How can i do that?

My huge problem is that i dont know how to take the values of the 3rd column.The value 1.5 in this example.

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If i've understood you correctly, you want a TextBox in the price-column and a textbox for the total price. You could use a TemplateColumn to show the price in a textbox and the footer to show the totalprice.

ASPX:

  <asp:GridView ID="GridView1" runat="server" ShowFooter="true" AutoGenerateColumns="false" >
        <Columns>
        <asp:BoundField HeaderText="ID" DataField="Name" />
        <asp:BoundField HeaderText="Name" DataField="Name" />
        <asp:TemplateField HeaderText="Price(Grouch)/Hectares">
            <ItemTemplate>
                <asp:TextBox ID="TxtPrice" runat="server"></asp:TextBox>
            </ItemTemplate>
            <FooterTemplate>
                <asp:TextBox ID="TxtTotal" runat="server" Text="0"></asp:TextBox>
            </FooterTemplate>
        </asp:TemplateField>
        </Columns>
    </asp:GridView>

Sorry for VB.Net, i hope you see what i mean anyway, the importan part is in RowDataBound of the GridView:

   Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Not IsPostBack Then
            BindGrid()
        End If
    End Sub

    Private Sub BindGrid()
        Dim dt As New DataTable
        dt.Columns.Add("ID", GetType(Int32)).AutoIncrement = True
        dt.Columns.Add("Name", GetType(String))
        dt.Columns.Add("Price(Grouch)/Hectares", GetType(Single))
        dt.PrimaryKey = New DataColumn() {dt.Columns("ID")}
        Dim newRow As DataRow = dt.NewRow
        newRow("ID") = 1
        newRow("Name") = "Seaside Location"
        newRow("Price(Grouch)/Hectares") = 1.5
        dt.Rows.Add(newRow)
        newRow = dt.NewRow
        newRow("ID") = 2
        newRow("Name") = "City Location"
        newRow("Price(Grouch)/Hectares") = 7.9
        dt.Rows.Add(newRow)
        Me.GridView1.DataSource = dt
        Me.GridView1.DataBind()
    End Sub

    Private totalPrice As Single = 0
    Private Sub GridRowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridView1.RowDataBound
        If e.Row.RowType = DataControlRowType.DataRow Then
            Dim row As DataRow = DirectCast(e.Row.DataItem, DataRowView).Row
            Dim txtPrice As TextBox = DirectCast(e.Row.FindControl("TxtPrice"), TextBox)
            Dim price As Single = DirectCast(row("Price(Grouch)/Hectares"), Single)
            txtPrice.Text = price.ToString
            totalPrice = totalPrice + price
        ElseIf e.Row.RowType = DataControlRowType.Footer Then
            Dim txtTotal As TextBox = DirectCast(e.Row.FindControl("TxtTotal"), TextBox)
            txtTotal.Text = totalPrice.ToString
        End If
    End Sub

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To get the value from the third column you can iterate over that array:

GridView.Rows[index].Cells[2].Value.ToString());

Example:

String TextIn4thRow3rdColumn = myGridView.Rows[3].Cells[2].Value.ToString());