Not sure what your problem is
1) Add a new button for 'saving updates'
2) Add an event handler for the button click from (1)
3) Open a file for output - I suggest you write a a temporary file eg E:\SAT\Work.io\Work.io\bin\Debug\ListofTasks.csv
.tmp" inside a using block
4) loop for each Row of dataGVGeneral
5) concantenate the columns of the row using join & ',' to get a CSV
6) write the line to the file
7) (outside the using & loop) archive the original file and rename the updated file without the '.tmp' on the end
You could change 7 to merge the files or such as you need
FWIW I think you could still do better using a datatable and the csvhelper library eg
CsvHelper[
^]
[Edit 2] This may be useful if you go the datatable route
Writing a DataTable to a CSV File[
^]