Raveendra,
Showing the tooltip for a datapoint is a client side action. Therefore you will need to create the hint content at client side. Could you please take a look at the following online sample and check if you are able to implement the functionality which you are looking for:
http://demo.componentone.com/ASPNET/ControlExplorer/C1BarChart/Overview.aspx
If you still face any issues then please elaborate on what exactly do you mean by tooltip for XField. Also this forum area is meant for the issues related to Studio for WPF. If you are currently using Wijmo controls and have any questions, please use the following forum area to post them:
http://our.componentone.com/groups/forum/aspnet-ajax/studio-for-asp-net/
Regards,
Sankalp