For some reason, this question gets asked a lot. How do I convert a byte to a System.String? (Yes, this is a CLR question. Sorry.)
You can use String System.Text.UnicodeEncoding.GetString() which takes a byte array and produces a string.
Note that this is not the same as just blindly copying the bytes from the byte array into a hunk of memory and calling it a string. The GetString() method must validate the bytes and forbid invalid surrogates, for example.
You might be tempted to create a string and just mash the bytes into it, but that violates string immutability and can lead to subtle problems.