I try to synchronize files between 2 computers, the folder is around 700 MiB, file size from 100K to 2M.
If transfer all of the files, it takes 25 seconds.

So I try to ignore the identical files and only transfer files that been modified.

HashAlgorithm? hash = HashAlgorithm.Create("SHA1");

Hash algorithm load file and compute hash code, then send to the other computer, on the other side it still need load file and compute hash, it takes 24 seconds, almost no change.

If only compare the file size, file with the same size may contains different content.

If compare the last update time, datetime on different PC may not the same.