How to write any characters through unicode?

Question

C++ / C#

Faced with the problem that the Russian char writes through binarywriter unicode and the English char writes using a single-byte encoding
What needs to be done so that the output of any character is through unicode?

Answer 1

Create a BinaryWriter with unicode encoding
// public BinaryWriter(Stream output, Encoding encoding);

new BinaryWriter(output, Encoding.Unicode);
// или
new BinaryWriter(output, Encoding.Utf8);

or directly convert characters to bytes.
Encoding.Utf8.GetBytes("мазафака");

Answer 2

and the English charm writes using a single-byte encoding

Are you REALLY sure that this is WRONG? How do you distinguish English char in UTF-8 from English char in ASCII?