Q:

Calling ClientID from aspx

"")" />
that doesn't work, the error says:
Parser Error Message: Server tags cannot contain <% ... %> constructs.
Any aproaches to solve this ? 
Thank you ;)

A:

You're calling a JS event (onchange), not a server event, so just pass in this.id.
<input type="checkbox" id="chbSaveState" runat="server" tabindex="3"  
onchange="SaveState(this.id)" /> 

To be clear, this.id and <%=chbSaveState.ClientID%> will return the same value in this case. Since you're calling this on an event of chbSaveState, you can just use the easily accessible JS property here, rather than <%=chbSaveState.ClientID%>, which requires the server to return the id which is generated by the server for that control.

