Hi,
I have created dataflow using source and target as SQL Server database. I need to disable index of the source in the starting of the flow and enable it after completion of flow. How I can disable and enable the index? what should be the code for that? Looking forward to answers.

Try bulk load option on the load object. If it does not drop and rebuild indexes, you can write a procedure to drop the indexs and run it a pre extract proc, build the indexes in the post load proc.