Insert text box in each row of an existing gridview

<asp:gridview id="GridView1" runat="server" onrowdatabound="GridView1_RowDataBound" xmlns:asp="#unknown">
 <columns>
  <asp:templatefield headertext="TextBox">
   <itemtemplate>
    <asp:textbox id="TextBox1" runat="server"></asp:textbox>
   </itemtemplate>
  </asp:templatefield>
   <itemtemplate>
    <asp:textbox id="TextBox2" runat="server"></asp:textbox>
   </itemtemplate>
  
 </columns>
</asp:gridview>

OnRowDataBound="gvGridView_RowDataBound"

<asp:GridView ID="gvGridView" runat="server" AutoGenerateColumns="False" OnRowCommand="gvGridView_RowCommand" OnRowDataBound="gvGridView_RowDataBound">

protected void gvGridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (DataControlRowType.DataRow == e.Row.RowType && e.Row.RowState != DataControlRowState.Edit && (e.Row.RowState == DataControlRowState.Normal || e.Row.RowState == DataControlRowState.Alternate))
    {
                TextBox tx = new TextBox();  //here i m adding a control.
                tx.ID = "txtCheck";
                tx.Attributes.Add("runat", "server");
                int i = e.Row.Cells.Count;
                i = i - 1;
                e.Row.Cells[i].Controls.Add(tx);   //textbox is added as last column of grid
}
}