C#: Programmatically apply merge/patch to file?

Question

I have a program that requires a few large (~4 or 5mb) files. Once a week, every week, there are new versions of these files with minor changes. Mostly just a few lines added or removed.

When the program starts, if there's an Internet connection, I'd like the program to update these files automatically. Instead of downloading the entire new versions of the files, I'll like to download just a patch based on the client's version of the files that updates them.

How might I do this?

I have total control over the server.

Answer 1

That is a tough problem to solve if you don't have any for knowledge of what is in the file or the server doest have a facility to allow you to request differences. Any program you write that does not have a way to determine the differences with out looking at the old and new file will have to download it anyway.

Answer 2

C# doesn't have any built-in facility to do this, but it sounds like your requirements aren't complicated. Look at how diff and ed on Unix can be used to patch a text file based on an easy-to-grok delta. Of course you should check the resulting file against a hash and fall back to a full download if it isn't correct.