I have aspx pages which uses repetative code. So i put them on a masterfile and referring that in all other files. I have used the in all other pages where i included maste
You can use ClientIDMode, but keep in mind that's only available in .NET 4.0 and above.
Or in JavaScript:
var userLabel = document.getElementById('<%=SelectedSport.ClientID%>');
if you are trying to access the control in javascript, then using .ClientID is probably your best bet, as it doesn't require change in aspx page