What is Hight and Low surrogate character in .NET?

Question

ICSM Computer · Answer

In .NET (and Unicode in general), high and low surrogate characters are used to represent
Unicode code points that cannot be represented in a single 16-bit
char (i.e., characters beyond the Basic Multilingual Plane, BMP — those with code points above
U+FFFF).
Surrogate Pairs: What They Are
.NET uses UTF-16 encoding for strings. UTF-16 represents:
Code points from U+0000 to U+FFFF (BMP) in a 
single char (16-bit).Code points from U+10000 to U+10FFFF using a 
pair of char values — one
high surrogate and one low surrogate.
This pair is called a surrogate pair.
High Surrogate
Unicode range: U+D800 to U+DBFFDecimal range: 55296 to 56319Always appears first in a surrogate pair
Low Surrogate
Unicode range: U+DC00 to U+DFFFDecimal range: 56320 to 57343Always appears second in a surrogate pair
Example
Consider the emoji 😁 (Unicode code point U+1F601):
In UTF-16, this is encoded as:
High Surrogate: \uD83DLow Surrogate: \uDE01
string emoji = "😁";
char highSurrogate = emoji[0]; // '\uD83D'
char lowSurrogate  = emoji[1]; // '\uDE01'
.NET API Methods Related to Surrogates
You can use these static methods from the Char class:
bool isHigh = Char.IsHighSurrogate(char c);
bool isLow = Char.IsLowSurrogate(char c);
bool isSurrogatePair(char high, char low);
Example:
char hs = '\uD83D';
char ls = '\uDE01';
bool valid = Char.IsSurrogatePair(hs, ls); // true
Summary Table
Type
Unicode Range
Decimal Range
Notes
High Surrogate
U+D800–U+DBFF
55296–56319
First char in a pair
Low Surrogate
U+DC00–U+DFFF
56320–57343
Second char in a pair
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What is Hight and Low surrogate character in .NET?

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Surrogate Pairs: What They Are

High Surrogate

Low Surrogate

Example

.NET API Methods Related to Surrogates

Summary Table

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Type	Unicode Range	Decimal Range	Notes
High Surrogate	U+D800–U+DBFF	55296–56319	First char in a pair
Low Surrogate	U+DC00–U+DFFF	56320–57343	Second char in a pair