How to maintain identity column value during SQL bulk copy t

Hi,

I am doing sqlbulkcopy from one table to another table.
There are so many tables to do that.
I am copying data with for loop for each tables.

But, i am facing with an issue, whenever i copy data from source table to destination table than identity column value is getting changed.

Suppoose there is value like this in identity column of a source table
301
305
605

but when i copy data than it will imported in destination table like that
1
2
3

1) I have tried,
set identity_insert [tablename] ON
//COPY Data from source to destination
set identity_insert [tablename] OFF

2) I have also set SqlBulkCopyOption.KeepIdentity

Any solution will be highly appriciable.