Byte arrays and File I/O

[Don]

I am trying to do file input and output in C# but I am stymied with Byte
arrays. I can declare an array a
byte [] Buffer = new byte[20]; then I can read into that buffer with
objSteamReader.Read(Buffer, iSeekPos, iLen);

BUT, once I have the info in my array of bytes, Buffer, how do I convert it
to the ints and strings etc that it contains?