I am creating a row of controls dynamically which includes one dropdownlist, 12 textboxes and one checkbox as soon as user clicks on "Add New Row" button.
Textboxes are kept for receiving inputs for the values of 12 months.

Here I am taking a panel and then I am adding the newly created table to this panel which serves as a placeholder for the table.

Inside the table I am adding these controls. Look the code it is very easy.

1.gif
Code Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page
{
private int numOfColumns = 12;
public static int ctr = 0;
static Table table = new Table();
protected void Page_Load(object sender, EventArgs e)
{
table.ID = "table1";
Panel1.Controls.Add(table);
}
protected void btnAddNewRow_Click(object sender, EventArgs e)
{
numOfColumns = 12;
//Generate the Table based from the inputs
GenerateTable(numOfColumns);
}
private void GenerateTable(int colsCount)
{
ctr++;
// Now iterate through the table and add your controls
TableRow row = new TableRow();
row.ID = "row" + ctr;
TableCell cell1 = new TableCell();
DropDownList dl = new DropDownList();
dl.ID = "DrpDwnBrand" + ctr;
dl.AutoPostBack = false;
dl.Width = 135;
// Add the control to the TableCell
cell1.Controls.Add(dl);
// Add the TableCell to the TableRow
row.Cells.Add(cell1);
for (int j = 1; j <= colsCount; j++)
{
TableCell cell2 = new TableCell();
TextBox tb = new TextBox();
if (j == 1)
{
tb.ID = "txtJan" + ctr;
}
else if (j == 2)
{
tb.ID = "txtFeb" + ctr;
}
else if (j == 3)
{
tb.ID = "txtMar" + ctr;
}
else if (j == 4)
{
tb.ID = "txtApr" + ctr;
}
else if (j == 5)
{
tb.ID = "txtMay" + ctr;
}
else if (j == 6)
{
tb.ID = "txtJun" + ctr;
}
else if (j == 7)
{
tb.ID = "txtJul" + ctr;
}
else if (j == 8)
{
tb.ID = "txtAug" + ctr;
}
else if (j == 9)
{
tb.ID = "txtSep" + ctr;
}
else if (j == 10)
{
tb.ID = "txtOct" + ctr;
}
else if (j == 11)
{
tb.ID = "txtNov" + ctr;
}
else if (j == 12)
{
tb.ID = "txtDec" + ctr;
}
tb.Width = 37;
// Add the control to the TableCell
cell2.Controls.Add(tb);
// Add the TableCell to the TableRow
row.Cells.Add(cell2);
}
TableCell cell3 = new TableCell();
CheckBox cb = new CheckBox();
cb.Controls.Clear();
cb.ID = "chkSameAll" + ctr;
cb.AutoPostBack = false;
cb.Width = 10;
// Add the control to the TableCell
cell3.Controls.Add(cb);
// Add the TableCell to the TableRow
row.Cells.Add(cell3);
// Add the TableRow to the Table
table.Rows.Add(row);
}
}

Default.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<br />
<br />
<asp:Button ID="btnAddNewRow" runat="server" OnClick="btnAddNewRow_Click" Style="z-index: 100;
left: 66px; position: absolute; top: 287px" Text="Add New Row" Width="145px" />
<asp:Panel ID="Panel1" runat="server" Height="50px" Style="z-index: 102; left: 73px;
position: absolute; top: 8px" Width="125px">
</asp:Panel>
</div>
</form>
</body>
</html>