What's the Difference Between Double Quotes and Single Quote in C#

Difference between ' (single quote) and “ (double quote) in ASP.NET 4

I want to know why I need to use single-quote, is it a rule? How can I
use double-quote in my situation?

The use of Single quote over Double quote is just to make it clear where the string is ending. You cannot use Text="MyMethod("123")" because the Text start with the M and may end with the ( or the 3 or the last ). By using single and double quote the compiler know when the string end.

Text="MyMethod('123')"

Text='MyMethod("123")'

Your example is about binding but let say that you would like to have a double quote while using a double quote for a non-binding situation. You could have use the HTML entity "

Text="This is my string with  " inside "" //This will produce : This is my string with "inside"

What are the functional differences between single-quoted vs double-quoted html attributes?

There is no functional difference. Quoting the W3C on SGML and HMTL:

By default, SGML requires that all attribute values be delimited using either double quotation marks (ASCII decimal 34) or single quotation marks (ASCII decimal 39). Single quote marks can be included within the attribute value when the value is delimited by double quote marks, and vice versa.
...
In certain cases, authors may specify the value of an attribute without any quotation marks. The attribute value may only contain letters (a-z and A-Z), digits (0-9), hyphens (ASCII decimal 45), periods (ASCII decimal 46), underscores (ASCII decimal 95), and colons (ASCII decimal 58). We recommend using quotation marks even when it is possible to eliminate them.

Single quotes vs. double quotes in C or C++

In C and in C++ single quotes identify a single character, while double quotes create a string literal. 'a' is a single a character literal, while "a" is a string literal containing an 'a' and a null terminator (that is a 2 char array).

In C++ the type of a character literal is char, but note that in C, the type of a character literal is int, that is sizeof 'a' is 4 in an architecture where ints are 32bit (and CHAR_BIT is 8), while sizeof(char) is 1 everywhere.

Single vs Double quotes (' vs )

The w3 org said:

By default, SGML requires that all attribute values be delimited using either double quotation marks (ASCII decimal 34) or single quotation marks (ASCII decimal 39). Single quote marks can be included within the attribute value when the value is delimited by double quote marks, and vice versa. Authors may also use numeric character references to represent double quotes (") and single quotes ('). For double quotes authors can also use the character entity reference ".

So... seems to be no difference. Only depends on your style.

Is there a way to alternate single and double quotes in C# like you can in javascript?

You can define your extension method on string to little speedup your work and reduce chance to misstype something.

    public static string ApostrophesToQuotes(this string s)
    {
        return s.Replace('\'', '"');
    }

And there is one more way to write quotes in string literal.

var s = @"he said ""Hello"" to me");

But you can't mix them, because apostrophes are for single character literal (2 byte integer in UTF-16) and quotes are for string literals (array of characters).

What is the difference between single-quoted and double-quoted strings in PHP?

PHP strings can be specified not just in two ways, but in four ways.

Single quoted strings will display things almost completely "as is." Variables and most escape sequences will not be interpreted. The exception is that to display a literal single quote, you can escape it with a back slash \', and to display a back slash, you can escape it with another backslash \\ (So yes, even single quoted strings are parsed).
Double quote strings will display a host of escaped characters (including some regexes), and variables in the strings will be evaluated. An important point here is that you can use curly braces to isolate the name of the variable you want evaluated. For example let's say you have the variable $type and you want to echo "The $types are". That will look for the variable $types. To get around this use echo "The {$type}s are" You can put the left brace before or after the dollar sign. Take a look at string parsing to see how to use array variables and such.
Heredoc string syntax works like double quoted strings. It starts with <<<. After this operator, an identifier is provided, then a newline. The string itself follows, and then the same identifier again to close the quotation. You don't need to escape quotes in this syntax.
Nowdoc (since PHP 5.3.0) string syntax works essentially like single quoted strings. The difference is that not even single quotes or backslashes have to be escaped. A nowdoc is identified with the same <<< sequence used for heredocs, but the identifier which follows is enclosed in single quotes, e.g. <<<'EOT'. No parsing is done in nowdoc.

Notes:
Single quotes inside of single quotes and double quotes inside of double quotes must be escaped:

$string = 'He said "What\'s up?"';
$string = "He said \"What's up?\"";

Speed:
I would not put too much weight on single quotes being faster than double quotes. They probably are faster in certain situations. Here's an article explaining one manner in which single and double quotes are essentially equally fast since PHP 4.3 (Useless Optimizations toward the bottom, section C). Also, this benchmarks page has a single vs double quote comparison. Most of the comparisons are the same. There is one comparison where double quotes are slower than single quotes.

Difference between double quotes and single quotes in Rust

The short answer is it works similarly to java. Single quotes for characters and double quotes for strings.

let a: char = 'k';
let b: &'static str = "k";

The b'' or b"" prefix means take what I have here and interpret as byte literals instead.

let a: u8 = b'k';
let b: &'static [u8; 1] = b"k";

The reason strings result in references is due to how they are stored in the compiled binary. It would be too inefficient to store a string constant inside each method, so strings get put at the beginning of the binary in header area. When your program is being executed, you are taking a reference to the bytes in that header (hence the static lifetime).

Going further down the rabbit hole, single quotes technically hold a codepoint. This is essentially what you might think of as a character. So a Unicode character would also be considered a single codepoint even though it may be multiple bytes long. A codepoint is assumed to fit into a u32 or less so you can safely convert any char by using as u32, but not the other way around since not all u32 values will match valid codepoints. This also means b'\u{x}' is not valid since \u{x} may produce characters that will not fit within a single byte.

// U+1F600 is a unicode smiley face
let a: char = '\u{1F600}';
assert_eq!(a as u32, 0x1F600);

However, you might find it interesting to know that since Rust strings are stored as UTF-8, codepoints over 127 will occupy multiple bytes in a string despite fitting into a single byte on their own. As you may already know, UTF-8 is simply a way of converting codepoints to bytes and back again.

let foo: &'static str = "\u{1F600}";
let foo_chars: Vec<char> = foo.chars().collect();
let foo_bytes: Vec<u8> = foo.bytes().collect();
    
assert_eq!(foo_chars.len(), 1);
assert_eq!(foo_bytes.len(), 4);

assert_eq!(foo_chars[0] as u32, 0x1F600);
assert_eq!(foo_bytes, vec![240, 159, 152, 128]);

What's the difference between single quote and double quote to define a string in powershell

Double quotes allow variable expansion while single quotes do not:

PS C:\Users\Administrator> $mycolor="red"
PS C:\Users\Administrator> write-output -inputobject 'My favorite color is $mycolor'
My favorite color is $mycolor

Source: http://www.techotopia.com/index.php/Windows_PowerShell_1.0_String_Quoting_and_Escape_Sequences

(I know version 1.0 but the principle is still the same)