C# Encrypt Text Output

Question

I have created a few little programs that export data to a text file using StreamWriter and then I read them back in using StreamReader. This works great and does what I nee

Answer 1

You can add a checksum or hash to the file - if the file contents doesn't agree with the checksum, you know it was tampered with.

If it is important that users can't read the contents of the file, you can encrypt it.

I don't believe you can make a file that can't be tampered with (a savvy user could use a hex editor and change it, for example) - the best you can do is detect such tampering.