Hello Madhukar,
What assemblies do you have referenced in your project? If you look at the getting started documentation for the XamDataChart, it lists what assemblies should be referenced in your project in order to use the chart control. InfragisticsWP8.v14.1 is one of those assemblies that you need to reference.
http://help.infragistics.com/doc/WindowsPhone/2014.1/CLR4.0?page=xamDataChart_Getting_Started_with_xamDataChart.html
Let me know if you have any further questions on this matter.