How to insert characters to a file using C#

Filesystems do not support "inserting" data in the middle of a file. If you really have a need for a file that can be written to in a sorted kind of way, I suggest you look into using an embedded database.

You might want to take a look at SQLite or BerkeleyDB.

Then again, you might be working with a text file or a legacy binary file. In that case your only option is to rewrite the file, at least from the insertion point up to the end.

I would look at the FileStream class to do random I/O in C#.

You will probably need to rewrite the file from the point you insert the changes to the end. You might be best always writing to the end of the file and use tools such as sort and grep to get the data out in the desired order. I am assuming you are talking about a text file here, not a binary file.

There is no way to insert characters in to a file without rewriting them. With C# it can be done with any Stream classes. If the files are huge, I would recommend you to use GNU Core Utils inside C# code. They are the fastest. I used to handle very large text files with the core utils ( of sizes 4GB, 8GB or more etc ). Commands like head, tail, split, csplit, cat, shuf, shred, uniq really help a lot in text manipulation.

For example if you need to put some chars in a 2GB file, you can use split -b BYTECOUNT, put the ouptut in to a file, append the new text to it, and get the rest of the content and add to it. This should supposedly be faster than any other way.

Hope it works. Give it a try.