ADO CommandText syntax

Question

Hi, Does anyone know why sometimes an @ is used preceding a commandText string?

both seem to work fine.

command.CommandText = @"SELECT id FROM users";

or

command.CommandText = "SELECT id FROM users";

Answer 1

That is C#'s verbatim string literal notation.

A verbatim string literal is preceded by a leading @ and anything between the quotes that follow that @ will be considered part of the string literal without any need for escaping.

Please see String literals:

C# supports two forms of string literals: regular string literals and verbatim string literals.

A regular string literal consists of zero or more characters enclosed in double quotes, as in "hello", and may include both simple escape sequences (such as \t for the tab character) and hexadecimal and Unicode escape sequences.

A verbatim string literal consists of an @ character followed by a double-quote character, zero or more characters, and a closing double-quote character. A simple example is @"hello". In a verbatim string literal, the characters between the delimiters are interpreted verbatim, the only exception being a quote-escape-sequence. In particular, simple escape sequences and hexadecimal and Unicode escape sequences are not processed in verbatim string literals. A verbatim string literal may span multiple lines.

Most likely a query was spanning multiple lines and whomever wrote the code wanted to put it on multiple lines like this:

command.CommandText = @"SELECT id
                       FROM users";

Whereas without a verbatim string literal you would have to do this:

command.CommandText = "SELECT id"
                      + " FROM users";

Answer 2

& = ampersand
@ = at (or at the rate of)

Answer 3

@ is the verbatim string operator. It comes in really handy when dealing with regular expressions. If you're looking for white space characters, you can specify

new RegEx( @"[\w]+")

instead of

new RegEx("[\\w]+")

to escape the '\'. The example works better for more complicated regular expressions.