problem with importing csv files with different headers

I am using the import feature of the ui-grid. the first time I import the csv file, every thing works fine. The headers of the csv file are made the headers of the ui-grid table. But, when I try to import a different csv file with a different set of headers, I am not able to see any data in the grid.e.g First file "Name","Gender","Company" "John Smith","male","TestIcon" .I get a proper table in this case Second file "First name","Last name","Country" "John","Doe","USA" Nothing is shown in this case. I even tried re-assigning the columnDefs to an empty array before import but nothing seems to work.