Dynamically add TextBox control to GridView Row in ASP.Net

Here i am binding the Gridview based on the DropDownList. I set the AutoGenerateColumn to true for the Gridview and  at the last row of  the Gridview i have added a empty row for the TextBox to be added.

HTML:

<form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="ddlTables" runat="server" AutoPostBack="true" OnSelectedIndexChanged="TablesSelectedIndexChanged">
            <asp:ListItem Text="Customers" Value="0" />
            <asp:ListItem Text="Customers" Value="1" />
            <asp:ListItem Text="Employees" Value="2" />
            <asp:ListItem Text="Suppliers" Value="3" />
        </asp:DropDownList>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="true">
        </asp:GridView>
        <asp:Button Text="AddRow" OnClick="AddRows" runat="server" />
    </div>
    </form>

C#:

protected void Page_Load(object sender, EventArgs e)
        {
            if (!this.IsPostBack)
            {
                this.GetTable("Customers");
            }
        }

        protected void TablesSelectedIndexChanged(object sender, EventArgs e)
        {
            GetTable(ddlTables.SelectedItem.Text);
        }

        protected void AddRows(object sender, EventArgs e)
        {
            int cellCount = this.GridView1.Rows[0].Cells.Count;
            int rowsCount = this.GridView1.Rows.Count;
            for (int j = 0; j < cellCount; j++)
            {
                //here i am adding a control.
                TextBox textBox = new TextBox();
                textBox.ID = "txtDynamicText" + j.ToString();
                textBox.Attributes.Add("runat", "server");
                textBox.CssClass = "Color";
                this.GridView1.Rows[rowsCount - 1].Cells[j].Controls.Add(textBox);
            }
        }

        private void GetTable(string tableName)
        {
            string strcon = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
            string sqlStatment = String.Format("SELECT * FROM {0}", tableName);
            using (SqlConnection con = new SqlConnection(strcon))
            {
                using (SqlCommand cmd = new SqlCommand(sqlStatment, con))
                {
                    using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                    {
                        con.Open();
                        DataTable dt = new DataTable();
                        da.Fill(dt);
                        //adding a line where textbox have to be added
                        DataRow row = dt.NewRow();
                        dt.Rows.InsertAt(row, dt.Rows.Count);
                        this.GridView1.DataSource = dt;
                        this.GridView1.DataBind();
                        con.Close();
                    }
                }
            }
        }

i have used the Northwind Database. You can dowload it from here.

http://northwinddatabase.codeplex.com/releases/view/71634