code point of € ,and é

https://www.compart.com/en/unicode/U+20AC

Name: Euro Sign[1]
Unicode Version: 2.1 (May 1998)[2]
Block: Currency Symbols, U+20A0 - U+20CF[3]
Plane: Basic Multilingual Plane, U+0000 - U+FFFF[3]
Script: Code for undetermined script (Zyyy) [4]
Category: Currency Symbol (Sc) [1]
Bidirectional Class: European Terminator (ET) [1]
Combining Class: Not Reordered (0) [1]
Character is Mirrored: No [1]
GCGID: SC200000[5]
HTML Entity:

€
€
€

UTF-8 Encoding: 0xE2 0x82 0xAC
UTF-16 Encoding: 0x20AC
UTF-32 Encoding: 0x000020AC

https://www.utf8-chartable.de/unicode-utf8-table.pl

U+20AC € e2 82 ac EURO SIGN

UTF-8的encoding

Since the restriction of the Unicode code-space to 21-bit values in 2003, UTF-8 is defined to encode code points in one to four bytes, depending on the number of significant bits in the numerical value of the code point. The following table shows the structure of the encoding. The x characters are replaced by the bits of the code point.

Code point <-> UTF-8 conversion
First code point	Last code point	Byte 1	Byte 2	Byte 3	Byte 4
U+0000	U+007F	0xxxxxxx
U+0080	U+07FF	110xxxxx	10xxxxxx
U+0800	U+FFFF	1110xxxx	10xxxxxx	10xxxxxx
U+10000	^{[nb 2]}U+10FFFF	11110xxx	10xxxxxx	10xxxxxx	10xxxxxx

因为€对应的code point是，0x20AC，对应于三字节的位置。所以需要做一个转换。

0x20AC的二进制是0010000010101100

按照上面的进行处理，得到三个字节11100010 10000010 10101100，对应的十六进制就是0x E2 82 AC

utf-8的字符串€转换成其他编码进行识别的话

 [Test]
        public void Test20210413001()
        {
            //€
            //UTF-8 Encoding:    0xE2 0x82 0xAC
            //UTF - 16 Encoding: 0x20AC
            //UTF - 32 Encoding: 0x000020AC
            string str = "€";
            var array = Encoding.UTF8.GetBytes(str);
            Console.WriteLine(GetHexString(array));

            //can not get string, as the 0x20ac will convert to three bytes in utf-8
            var bytes = new byte[] {0x20, 0xac};
            var str2 = Encoding.UTF8.GetString(bytes);
            Console.WriteLine(str2);

            //936     gb2312     ANSI/OEM Simplified Chinese (PRC, Singapore); Chinese Simplified (GB2312)
            var str3 = Encoding.GetEncoding(936).GetString(array);
            Console.WriteLine(str3);

            //1252     windows-1252     ANSI Latin 1; Western European (Windows)
            var str4 = Encoding.GetEncoding(1252).GetString(array);
            Console.WriteLine(str4);

            //28591     iso-8859-1     ISO 8859-1 Latin 1; Western European (ISO)
            var str5 = Encoding.GetEncoding(28591).GetString(array);
            Console.WriteLine(str5);
        }

euro sign在windows-1252以及iso-8859-1里面对应的编码，分别是80和3F

 //€
            //UTF-8 Encoding:    0xE2 0x82 0xAC
            //UTF - 16 Encoding: 0x20AC
            //UTF - 32 Encoding: 0x000020AC
            string str = "€";
            //1252     windows-1252     ANSI Latin 1; Western European (Windows)
            var array = Encoding.GetEncoding(1252).GetBytes(str);
            Console.WriteLine(GetHexString(array));

            //28591     iso-8859-1     ISO 8859-1 Latin 1; Western European (ISO)
            var array6 = Encoding.GetEncoding(28591).GetBytes(str);
            Console.WriteLine(GetHexString(array6));