<asp:gridview id="gvnew" runat="server" cellpadding="4" forecolor="#333333" gridlines="None" onselectedindexchanged="gvnew_SelectedIndexChanged" xmlns:asp="#unknown"> <asp:templatefield>
///use itemtemplate here
<itemtemplate>
<asp:checkbox id="CheckBox1" runat="server" /> <asp:checkbox id="chkbselect" runat="server" oncheckedchanged="CheckBox1_CheckedChanged" />
<pagerstyle backcolor="#2461BF" forecolor="White" horizontalalign="Center" /> <asp:checkbox id="Chkbselect" runat="server" checked="True" />
and in c# code
TextBox2.Text = gvnew.Rows[0].Cells[0].Text.ToString();
Textbox txt=(TextBox)row.findcontrol("textboxid");
and rather than textbox readonly you can use on client side
onkeypress="javascript: return false;"
on textbox.
try it
Please Vote if it helps you