How to assign dynamic sequence id for Web Form Con

[Infappign]

I want to assign an id to Web Form Control,<BR>such as <BR><BR><%i = 1%><BR><asp:textbox id='txt<%=i%>' runat=server><BR><BR>I got error message, however, we know it works on simple html control, for example <input name='txt<%=i%>'><BR><BR>Anybody can give me a help?<BR><BR>Thanks<BR><BR>Shuren