String @ C#

 

The string type represents a string of Unicode characters. string is an alias for System.String in the .NET Framework.

Although string is a reference type, the equality operators (== and !=) are defined to compare the values of string objects, not references (7.9.7 String equality operators). This makes testing for string equality more intuitive.

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string a = "hello";
string b = "h";
b += "ello"; // append to b
Console.WriteLine( a == b );          // output: True -- same value
Console.WriteLine( (object)a == b );  // False -- different objects

The + operator concatenates strings:

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string a = "good " + "morning";

The [] operator accesses individual characters of a string:

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char x = "test"[2];  // x = 's';

String literals are of type string and can be written in two forms, quoted and @-quoted. Quoted string literals are enclosed in double quotation marks ("):

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"good morning"  // a string literal

and can contain any character literal, including escape sequences:

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string a = "\\\u0066\n";  // backslash, letter f, new line

Note   The escape code \udddd (where dddd is a four-digit number) represents the Unicode character U+dddd. Eight-digit Unicode escape codes are also recognized: \udddd\udddd.

@-quoted string literals start with @ and are enclosed in double quotation marks. For example:

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@"good morning"  // a string literal

The advantage of @-quoting is that escape sequences are not processed, which makes it easy to write, for example, a fully qualified file name:

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@"c:\Docs\Source\a.txt"  // rather than "c:\\Docs\\Source\\a.txt"

To include a double quotation mark in an @-quoted string, double it:

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@"""Ahoy!"" cried the captain." // "Ahoy!" cried the captain.

Another use of the @ symbol is to use referenced (/reference) identifiers that happen to be C# keywords. For more information, see 2.4.2 Identifiers.

Example

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// keyword_string.cs
using System;
class test 
{
   public static void Main( String[] args ) 
   {
      string a = "\u0068ello ";
      string b = "world";
      Console.WriteLine( a + b );
      Console.WriteLine( a + b == "hello world" );
   }
}

Output

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hello world
True