Byte array replace byte with byte sequence efficiency: iterate and copy versus SelectMany

I'm dealing with a byte array that comprises a text message, but some of the characters in the message are control characters (i.e. less than 0x20) and I want to replace them with sequences of characters that are human readable 开发者_高级运维when decoded into ASCII (for instance 0x0F would display [TAB] instead of actually being a tab character). So as I see it, I have three options:

1. Decode the whole thing into an ASCII string, then use String.Replace() to swap out what I want. The problem with this is that the characters seem to just be decoded as the unprintable box character or question marks, thus losing their actual byte values.
2. Iterate through the byte array looking for any of my control characters and performing an array insert operation (make new larger array, copy existing pieces in, write new pieces).
3. Use Array.ToList<byte>() to convert the byte array to a List, then use IEnumerable.SelectMany() to transform the control characters into sequences of readable characters which SelectMany will then flatten back out for me.

So the question is, which is the best option in terms of efficiency? I don't really have a good feel for the performance implications of the IEnumerable lambda operations. I believe option 1 is out as functionally unworkable, but I could be wrong.

Try

// your byte array for the message
byte[] TheMessage = ...;
// a string representation of your message (the character 0x01... 0x32 are NOT altered)
string MessageString = Encoding.ASCII.GetString(TheMessage);
// replace whatever you want...
MessageString = MessageString.Replace (" ", "x").Replace ( "\n", " " )...
// the replaced message back as byte array
byte[] TheReplacedMessage= Encoding.ASCII.GetBytes(MessageString.ToCharArray());

EDIT:

Sample for replacing an 8 Bit byte value

 MessageString = MessageString.Replace ( Encoding.ASCII.GetString (new byte[] {0xF7}), " " )...

Regarding the performance I am not 100% sure whether it is the fastest approach... we just tried several approaches though our requirement was to replace "byte array of 1-n bytes" whithin the original byte-array... this came out the fastet+cleanest for our use case (1 MB - 1 GB files).