1.5 Special Characters

📌1. Escape Sequences (inside strings/char literals)

C# uses the backslash (\) to introduce escape sequences.

Escape	Meaning	Example	Output
\'	Single quote	Console.WriteLine('\'');	'
\"	Double quote	Console.WriteLine("\"");	"
\\	Backslash	Console.WriteLine("\\");	\
\0	Null char	"A\0B".Length → 3	A␀B
\a	Alert (beep)	Console.Write("\a");	(beep sound)
\b	Backspace	"AB\bC"	AC
\f	Form feed	Rarely used (page break)	–
\n	Newline (LF)	"Hello\nWorld"	Hello ↵ World
\r	Carriage return (CR)	"Hello\rWorld"	Worldo
\t	Tab	"A\tB"	A B
\v	Vertical tab	Rare, whitespace	–
\uXXXX	Unicode (16-bit)	\u03A9	Ω
\UXXXXXXXX	Unicode (32-bit)	\U0001F600	😀
\xNN	Hex (variable length)	\x41	A

🔹 Example:

string demo = "Line1\nLine2\tTabbed";
Console.WriteLine(demo);

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📌2. Verbatim Strings (@"")

Use @ before a string to treat backslashes literally and allow multiline text.

string path = @"C:\Users\Tyson\Docs\file.txt";
string multi = @"Line1
Line2
Line3";

⚠️ To include a quote in a verbatim string: ""

string quote = @"She said, ""Hello!""";

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📌3. Interpolated Strings ($"")

Use $ to embed variables/expressions with {}:

int age = 25;
string name = "Tyson";
string msg = $"Hello, {name}. You are {age} years old.";

✅ You can combine with @ for multi-line interpolated strings:

string folder = "Docs";
string path = $@"C:\Users\Tyson\{folder}\file.txt";

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📌4. Special Characters in Identifiers

Normally you cannot name a variable the same as a keyword, but you can prefix it with @.

int @class = 10;   // allowed, but not recommended
Console.WriteLine(@class);

This is useful when working with reserved words (e.g., mapping DB fields).

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📌5. Digit Separators & Discards (_)

• _ can be used as a digit separator in numbers:

  int million = 1_000_000;
  double pi = 3.14_15_92;

• _ can be used as a discard when you don’t care about a variable:

  var (_, lastName) = ("John", "Doe"); // ignore first value

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📌6. Null-related Operators (?)

• Nullable types:

  int? maybe = null;

• Null-conditional:

  person?.SayHello();

• Null-coalescing:

  string result = name ?? "Unknown";

• Null-coalescing assignment:

  name ??= "Default";

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📌7. Other Special Syntax Characters

Symbol	Meaning
;	Statement terminator
{ }	Code blocks, object initializers
( )	Method calls, grouping
[ ]	Arrays, attributes, indexers
,	Separates items in lists
.	Member access
:	Used in ternary, inheritance, case labels
? :	Ternary conditional operator
=>	Lambda expressions
->	Function pointers (C# 9+)
#	Preprocessor directives (#define, #region, etc.)
$	Interpolated strings
@	Verbatim strings, identifiers
_	Digit separator, discard

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📌8. Preprocessor Special Characters (#)

Lines starting with # are compiler instructions:

#define DEBUG
#if DEBUG
Console.WriteLine("Debug mode");
#endif
 
#region Helpers
// ...
#endregion

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📌9. Regex & Escaping Gotchas

When writing regex or Windows paths, escaping can get messy.
Best practice → use @"" verbatim strings.

string pattern = @"\d{3}-\d{2}-\d{4}";

Instead of:

string pattern = "\\d{3}-\\d{2}-\\d{4}";

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📌10. Summary

• Use \ escape sequences for control characters.

• Use @ for verbatim strings (literal backslashes, multiline).

• Use $ for interpolation.

• Use @ before identifiers to allow keywords.

• Watch for null operators (?, ??, ??=).

• Learn common syntax symbols (;, {}, =>, #).

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