Note to self:
var ascii7BitEncoding = Encoding.ASCII; // ASCII
var ascii8BitEncodingIsh = Encoding.GetEncoding("iso-8859-1"); // Extended ASCII for almost all practical purposes
Where Extended ASCII differs from ISO-8859-*, according to Wikipedia:
One notable way in which ISO character sets differ from code pages is that the character positions 128 to 159, corresponding to ASCII control characters with the high-order bit set, are specifically unused and undefined in the ISO standards, though they had often been used for printable characters in proprietary code pages, a breaking of ISO standards that was almost universal.