Kiran:
Please reference the
Programmatic Creation documentation page for insights. It states:
RadGrid does not support mixing declarative grid columns with grid columns added dynamically at runtime. You should either create all the columns in the grid programmatically, or else define them all in the ASPX file.
Be sure to view the Grid/OnPageLoad online demo for help in converting to the programmatic creation for all needed columns.
Cheers!