Char type and Unicode behavior in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the C# char type used for?

The char type in C# represents a single 16-bit Unicode character. It stores a UTF-16 code unit, which can represent most common characters.

intermediate

How does C# char handle Unicode characters outside the Basic Multilingual Plane (BMP)?

Characters outside the BMP (code points above U+FFFF) are represented using a pair of char values called surrogate pairs. Each char holds one 16-bit code unit of the UTF-16 encoding.

intermediate

What is a surrogate pair in Unicode?

A surrogate pair is two 16-bit char values that together represent a single Unicode character outside the BMP (above U+FFFF). The first is a high surrogate, the second a low surrogate.

intermediate

How can you check if a char is a high surrogate or low surrogate in C#?

Use char.IsHighSurrogate(char c) to check for a high surrogate and char.IsLowSurrogate(char c) for a low surrogate.

beginner

Why can't a single C# char always represent a full Unicode character?

Because char stores a UTF-16 code unit, some Unicode characters (those outside BMP) require two char values (surrogate pairs) to represent one character fully.

What size is the C# char type?

A 16 bits

B 8 bits

C 32 bits

D 64 bits

The C# char type is a 16-bit value representing a UTF-16 code unit.

Which of these represents a Unicode character outside the Basic Multilingual Plane in C#?

A A string of length 3

B A single <code>char</code>

C An 8-bit byte

D A surrogate pair of two <code>char</code> values

Characters outside the BMP require two char values called surrogate pairs.

How do you check if a char is a high surrogate in C#?

A char.IsDigit(c)

B char.IsHighSurrogate(c)

C char.IsSurrogate(c)

D char.IsLowSurrogate(c)

Use char.IsHighSurrogate(c) to check for a high surrogate.

What encoding does C# char use internally?

A UTF-8

B ASCII

C UTF-16

D UTF-32

C# char stores UTF-16 code units.

Why might a Unicode character need two char values in C#?

A Because it is outside the BMP and requires surrogate pairs

B Because <code>char</code> is 8-bit

C Because it is a combining character

D Because it is a control character

Characters outside the BMP need two char values (surrogate pairs) to be represented.

Explain how the C# char type represents Unicode characters, including those outside the Basic Multilingual Plane.

Think about UTF-16 encoding and surrogate pairs.

Describe how to identify surrogate pairs in C# and why they are important.

Focus on surrogate pair detection methods and their role.