DevTut

# String Escape Sequences

# Escaping special symbols in string literals

Backslash

// The filename will be c:\myfile.txt in both cases
string filename = "c:\\myfile.txt";
string filename = @"c:\myfile.txt";

The second example uses a verbatim string literal (opens new window), which doesn't treat the backslash as an escape character.

Quotes

string text = "\"Hello World!\", said the quick brown fox.";
string verbatimText = @"""Hello World!"", said the quick brown fox.";

Both variables will contain the same text.

"Hello World!", said the quick brown fox.

Newlines

Verbatim string literals can contain newlines:

string text = "Hello\r\nWorld!";
string verbatimText = @"Hello
World!";

Both variables will contain the same text.

# Unicode character escape sequences

string sqrt = "\u221A";      // √
string emoji = "\U0001F601"; // 😁
string text = "\u0022Hello World\u0022"; // "Hello World"
string variableWidth = "\x22Hello World\x22"; // "Hello World"

# Escaping special symbols in character literals

Apostrophes

char apostrophe = '\'';

Backslash

char oneBackslash = '\\';

# Using escape sequences in identifiers

Escape sequences are not restricted to string and char literals.

Suppose you need to override a third-party method:

protected abstract IEnumerable<Texte> ObtenirΕ’uvres();

and suppose the character Ε’ is not available in the character encoding you use for your C# source files. You are lucky, it is permitted to use escapes of the type \u#### or \U######## in identifiers in the code. So it is legal to write:

protected override IEnumerable<Texte> Obtenir\u0152uvres()
{
    // ...
}

and the C# compiler will know Ε’ and \u0152 are the same character.

(However, it might be a good idea to switch to UTF-8 or a similar encoding that can handle all characters.)

# Unrecognized escape sequences produce compile-time errors

The following examples will not compile:

string s = "\c";
char c = '\c';

Instead, they will produce the error Unrecognized escape sequence at compile time.

# Syntax

  • ' β€” single quote (0x0027)
  • " β€” double quote (0x0022)
  • \ β€” backslash (0x005C)
  • \0 β€” null (0x0000)
  • \a β€” alert (0x0007)
  • \b β€” backspace (0x0008)
  • \f β€” form feed (0x000C)
  • \n β€” new line (0x000A)
  • \r β€” carriage return (0x000D)
  • \t β€” horizontal tab (0x0009)
  • \v β€” vertical tab (0x000B)
  • \u0000 - \uFFFF β€” Unicode character
  • \x0 - \xFFFF β€” Unicode character (code with variable length)
  • \U00000000 - \U0010FFFF β€” Unicode character (for generating surrogates)

# Remarks

String escape sequences are transformed to the corresponding character at compile time. Ordinary strings that happen to contain backwards slashes are not transformed.

For example, the strings notEscaped and notEscaped2 below are not transformed to a newline character, but will stay as two different characters ('\' and 'n').

string escaped = "\n";
string notEscaped = "\\" + "n";
string notEscaped2 = "\\n";

Console.WriteLine(escaped.Length); // 1
Console.WriteLine(notEscaped.Length); // 2            
Console.WriteLine(notEscaped2.Length); // 2

← StringBuilder β†’