It works only for smaller files having 6-7 columns and 70 odd rows, but for larger files it gives issues as my file has 700 odd rows

It was working fine for 32 columns and having 70 rows
FYI : 6 columns out of 32 has data, rest were blank

Few things suggested: Exceptions needs to be handled in the .net code, and check for larger file which has more than 500 rows