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Python C# - Unicode character is not the same on Python and C#

I encountered with a problem while working on text files. I found that the character Unicode representation on Python and C# is different.
While opening the file with Python 3.5.2 on specific index the unicode character is:
with open('file.txt', 'r', encoding = 'utf-8') as f:
text = f.read()
text[189]
// Output: u"\U0001F464"
While opening the file with C# on the same index this char is represented by two characters:
string text = File.ReadAllText("file.txt", Encoding.UTF8);
Console.WriteLine(((int)text[189]).ToString("X4"));
// Output: "D83D"
string text = File.ReadAllText("file.txt", Encoding.UTF8);
Console.WriteLine(((int)text[190]).ToString("X4"));
// Output: "DC64"
So on python this char is on index 189 and on c# its on 189 and 190.
Reference to this charecter on fileformat website:
http://www.fileformat.info/info/unicode/char/1F464/index.htm
As you can see there, the representation of this charecter has a different length. On C#/C/C++/Java "\uD83D\uDC64" and on python u"\U0001F464".
The part of the text that is problematic:
👤 Sign in
Is there a way to use the same unicode representation in Python 3.5 and C#?
Edit:
Download of the original file in which this error happend:
https://ufile.io/pr5v6

You can't fix it. It is inherent in the Unicode implementation of the languages.
When reading a file and decoding to Unicode, C# and Java store Unicode strings internally encoded as UTF-16. Code points outside the basic multilingual plane (BMP, U+0000 to U+FFFF) use surrogates (two words) to represent a Unicode code point. The fact that you can see a Unicode code point as two words is a leaky abstraction.
Python 3.3+ hides this abstraction. It internally uses 1-, 2- or 4-byte encodings as needed to represent a Unicode string, but presents only the Unicode code points to the user.
Python 2 (same leaky abstraction as C# and Java):
Python 2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:53:40) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> len(u'\U0001F464')
2
>>> u'\U0001F464'[0]
u'\ud83d'
>>> u'\U0001F464'[1]
u'\udc64'
Python 3.3+:
Python 3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 18:41:36) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> len(u'\U0001F464')
1
>>> u'\U0001F464'[0]
'👤'
Internally, Python 3 uses UTF-32 to store a Unicode string containing a non-BMP code point and would use four bytes to store U+1F464.

Decode UTF-8 bytes as Latin-1 characters

I have a string that I receive from a third party app and I would like to display it correctly in any language using C# on my Windows Surface.
Due to incorrect encoding, a piece of my string looks like this in Farsi (Persian-Arabic):
مدل-رنگ-موی-جدید-5-436x500
whereas it should look like this:
مدل-رنگ-موی-جدید-5-436x500
This link convert this correctly:
http://www.ltg.ed.ac.uk/~richard/utf-8.html
How I can do it in c#?

It is very hard to tell exactly what is going on from the description of your question. We would all be much better off if you provided us with an example of what is happening using a single character instead of a whole string, and if you chose an example character which does not belong to some exotic character set, for example the bullet character (u2022) or something like that.
Anyhow, what is probably happening is this:
The letter "ر" is represented in UTF-8 as a byte sequence of D8 B1, but what you see is "ر", and that's because in UTF-16 Ø is u00D8 and ± is u00B1. So, the incoming text was originally in UTF-8, but in the process of importing it to a dotNet Unicode String in your application it was incorrectly interpreted as being in some 8-bit character set such as ANSI or Latin-1. That's why you now have a Unicode String which appears to contain garbage.
However, the process of converting 8-bit characters to Unicode is for the most part not destructive, so all of the information is still there, that's why the UTF-8 tool that you linked to can still kind of make sense out of it.
What you need to do is convert the string back to an array of ANSI (or Latin-1, whatever) bytes, and then re-construct the string the right way, which is a conversion of UTF-8 to Unicode.
I cannot easily reproduce your situation, so here are some things to try:
byte[] bytes = System.Text.Encoding.Ansi.GetBytes( garbledUnicodeString );
followed by
string properUnicodeString = System.Text.Encoding.UTF8.GetString( bytes );

What encoding be used to create MS-DOS txt file using C#(UTF8Encoding vs Encoding)

I am trying to create a flat file for a legacy system and they mandates that the data to be presented in TextEncoding of MS DOS .txt file (Text Document - MS-DOS Format CP_OEM). I am a bit confused between files generated by using UTF8Encoding class in C# (.net4.0 framework) and I think it produce a file in default txt file (Encoding: CP_ACP).
I think Encoding names CP_ACP , Winodows and ANSI refers to same thing and Windows default is ANSI and it will omit any unicode character information.
If I use UTF8Encoding class in C# library to create a text file(as below), is it going to be in the MS DOS txt file format?
byte[] title = new UTF8Encoding(true).GetBytes("New Text File");
As per the answer supplied it is evident that UTF8 is NOT equivalent to MSDOS txt format and should use Encoding.GetEncoding(850) method to get the encoding library.
I read the following posts to check on my information but nothing conclusive yet.
https://blogs.msdn.microsoft.com/oldnewthing/20120220-00?p=8273
https://blog.mh-nexus.de/2015/01/character-encoding-confusion
https://blogs.msdn.microsoft.com/oldnewthing/20090115-00?p=19483
Finally the conclusion is to go with Encoding.GetEncoding(850) when creating a byte array to be converted back to the actual file(note: i am using byte array as i can leverage existing middle wares).

You can use the File.ReadXY(String, Encoding) and File.WriteXY(String, String[], Encoding) methods, where XY is either AllLines, Lines or AllText working with string[], IEnumerable<string> and string respectively.
MS-DOS uses different code pages. Probably the code page 850 "Western European / Latin-1" or code page 437 "OEM-US / OEM / PC-8 / DOS Latin US" (as #HansPassant suggests) will be okay. If you are not sure, which code page you need, create example files containing letters like ä, ö, ü, é, è, ê, ç, à or greek letters with the legacy system and see whether they work. If you don't use such letters or other special characters, then the code page is not very critical.
File.WriteAllText(path, "Hello World", Encoding.GetEncoding(850));
The character codes from 0 to 127 (7-bit) are the same for all MS-DOS code pages, for ANSI and UTF-8. UTF files are sometimes introduced with a BOM (byte order mark).
MS-DOS knows only 8-bit characters. The codes 128 to 255 differ for the different national code pages.
See: File Class, Encoding Class and Wikipedia: Code Page.

What happens to a null byte when converting bytes to ISO 8859-1 encoding?

I'm not entirely sure if the question even makes sense. I'm converting a byte array taken from an ID3 tag and converting it to a string. Most text frames in an ID3 tag use ISO 8859-1 encoding but it depends on the frame. In any case, if you look up what 0x00 is in the ISO 8859-1 codes it is invalid.
To further complicate, either due programmer error or just poor formatting, some of the strings end in 0x00 and some do not.
When converting a series of bytes into a string using ISO 8859-1 encoding do you have manually check the end of the string to see if it is a null? Or will the encoding object through whatever method it uses to convert in the first place deal with the null properly? Furthermore, is there some sort of function that could normalize or "fix" the null terminated string?
When you try to display these strings they do not display properly.
I am using C# for this particular project.
Some extra info here about ID3 Tags: ID3 Specs
Or am I completely misunderstanding the whole thing? Is a null terminator simply a way a particular language handles strings and it has nothing to do with encoding?
Edit: I used System.Text.Encoding.GetEncoding("iso-8859-1") followed by a GetString call

If you use Encoding.GetEncoding(28591), it just converts a byte 0 to the Unicode U+0000. Encodings generally assume that they have to convert all the bytes - they don't look for terminators.
This treatment of 0 as Unicode 0 is inline with the Wikipedia description:
In 1992, the IANA registered the character map ISO_8859-1:1987, more commonly known by its preferred MIME name of ISO-8859-1 (note the extra hyphen over ISO 8859-1), a superset of ISO 8859-1, for use on the Internet. This map assigns the C0 and C1 control characters to the unassigned code values thus provides for 256 characters via every possible 8-bit value.
The C0 and C1 control characters page includes:
0: Originally used to allow gaps to be left on paper tape for edits. Later used for padding after a code that might take a terminal some time to process (e.g. a carriage return or line feed on a printing terminal). Now often used as a string terminator, especially in the C programming language.
Sample code:
using System;
using System.Text;
class Program
{
static void Main(string[] args)
{
byte[] data = { 0, 0 };
Encoding latin1 = Encoding.GetEncoding(28591);
string text = latin1.GetString(data);
Console.WriteLine(text.Length); // 2
Console.WriteLine((int) text[0]); // 0
Console.WriteLine((int) text[1]); // 0
}
}

Happily, ASCII, ISO-8859-1 and Unicode all agree on codepoints in the range 0..127. Thus your character '\0' will be encoded identically in ASCII, ISO-8859-1 and UTF-8.
If your program assigns special semantics to the zero byte, you have to take care of that appropriately.

"Unable to translate Unicode character" error when saving to txt file

Additional information: Unable to
translate Unicode character \uDFFF at
index 195 to specified code page.
I made an algorithm, who's result are binary values (different lengths). I transformed it into uint, and then into chars and saved into stringbuilder, as you can see below:
uint n = Convert.ToUInt16(tmp_chars, 2);
_koded_text.Append(Convert.ToChar(n));
My problem is, that when i try to save those values into .txt i get the previously mentioned error.
StreamWriter file = new StreamWriter(filename);
file.WriteLine(_koded_text);
file.Close();
What i am saving is this: "忿췾᷿］볯褟ﶞ痢ﳻ��伞ﳴ㿯ﹽ翼蛿㐻ﰻ筹��﷿￦ﾏ랿鳿⏟麞펿"... which are some weird signs.
What i need is to convert those binary values into some kind of string of chars and save it to txt. I saw somewhere that converting to UTF8 should help, but i don't know how to. Would changing files encoding help too?

You cannot transform binary data to a string directly. The Unicode characters in a string are encoded using utf16 in .NET. That encoding uses two bytes per character, providing 65536 distinct values. Unicode however has over one million codepoints. To make that work, the Unicode codepoints above \uffff (above the BMP, Basic Multilingual Plane) are encoded with a surrogate pair. The first one has a value between 0xd800 and 0xdbff, the second between 0xdc00 and 0xdfff. That provides 2 ^ (10 + 10) = 1 million additional codes.
You can perhaps see where this leads, in your case the code detects a high surrogate value (0xdfff) that isn't paired with a low surrogate. That's illegal. Lots more possible mishaps, several codepoints are unassigned, several are diacritics that get mangled when the string is normalized.
You just can't make this work. Base64 encoding is the standard way to carry binary data across a text stream. It uses 6 bits per character, 3 bytes require 4 characters. The character set is ASCII so the odds of the receiving program decoding the character back to binary incorrectly are minimal. Only a decades old IBM mainframe that uses EBCDIC could get you into trouble. Or just plain avoid encoding to text and keep it binary.

Since you're trying to encode binary data to a text stream this SO question already contains an answer to the question: "How do I encode something as base64?" From there plain ASCII/ANSI text is fine for the output encoding.