C# - Convert UTF8 String into bits, modify bits, and convert back into UTF8 String

Question

For a project I'm working on, I need to be able to convert a UTF8 string into bits or bytes for modification and back. (Bit/Byte type doesn't matter.. '138' or '00000001' or '0A' - as long as I'm able to modify it as a string and convert the Bytes back into a string)

I've tried a few things, but nothing has worked. For the most part, I've been trying to take the result of File.ReadAllBytes(path) and convert the bytes into a modifiable string and back, but haven't had any success. Also tried doing the same using a test string into a BitArray with no better luck.

Here's what I'm trying to do in a better example (pseudocode)

string input = "ABC";

Byte[] bytes = StringToBytes(input);
Byte[] bytes2;

string bytestring;
foreach (Byte byte in bytes) {
    bytestring = byte.ToString();
    /// modify bytestring to the value of a different byte here ///
    bytes2.Add(bytestring.ToByte());
}

return BytesToString(bytes2);

Return: 'ACD' (or whatever)

Answer 1

If you're trying to read a file into a byte[] array, modify those bytes, and convert that back to a string, you could do something like this:

// read the file into a byte array
var bytes = File.ReadAllBytes(inputFileName);

// modify the bytes

// now convert back to a UTF string
var stringFromByteArray = Encoding.UTF8.GetString(bytes, 0, bytes.Length);