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Alvaro Montoro
Asked: 2020-06-08 08:27:19 +0800 CST 2020-06-08 08:27:19 +0800 CST

What does the $ in front of a string mean?

  • 772

I'm working on a project and they gave me a C# file with code similar to what I had to do. Investigating it I found this:

valorOpcion1 = "valor_que_viene_de_un_lado";
valorOpcion2 = "valor_que_viene_de_otro_lado";

var miLista = new List<string>
    {
        $"opcion1:{valorOpcion1}",
        $"opcion1:{valorOpcion2}"
    };

What it does is define and initialize a list of strings with two default values. My doubt comes with the $one with those chains, I don't know what it is.

What does putting the dollar sign ( $) in front of a string do? Is there a difference between, say, "hola"and $"hola"?

c#

3 Answers

  1. Best Answer

    It means that it is an interpolated string.

    String interpolation means that you can use previously defined variables in your code, and the JIT compiler will take care of replacing them with the respective values ​​at run time.

    In your example, each of the options will have as value:

    opcion1:valor_que_viene_de_un_lado
opcion1:valor_que_viene_de_otro_lado

    Interpolation allows you to call functions within the chain, for example:

    $"La hora actual es: {DateTime.Now:d}"

    And you can even use a ternary operator inside, to do a quick analysis:

    int i = 1;
string s = $"{(i==1?"si":"no")}";

    The complete documentation is here

    • 16

  2. In C#there are two types of symbols to format a string stringsdirectly.

    $: Interpolated Strings : An interpolated string is a string that contains interpolated expressions. When an interpolated string is resolved to a result string, the elements with interpolated expressions are replaced with the string representations of the expression results. This feature is available in C# 6 and later versions of the language.

    Previously, the Composite String format was used , making it use unidentifiable arguments and making the process of formatting a string more tedious.

    Let's use the following example class:

    public class Persona {
   public string Nombre { get; private set; } = "Alvaro Montoro";
   public int Edad { get; private set; } = 20;
}

    Using the Formato Compuesto, to form a string with the person values ​​you would have to do the following:

    Persona persona = new Persona();
string datos = string.Format("Nombre: {0} y Edad: {1} ", persona.Nombre, persona.Edad);

    If you notice, Formato Compuestoit is guided by indexes, which does not give you clarity of what value is being used if you do not know the order. So using the format of Cadena Interpolada, the format is direct and you already know the assigned property:

    Persona persona = new Persona();
string datos = $"Nombre: {persona.Nombre} y Edad: {persona.Edad}";

    @ : String-oriented Textual Identifier : This identifier, in a nutshell, is used to insert symbols into a string, which does not accept special characters.

    For example, if I want to print quotes in a string, I must insert the symbol \in between, which means that the will \not be part of the result. If I want to make the symbol \part of the result, I must use the Identificador textual:

    string sin_identificador = "Hola, \"StackOverflow\"";
string con_identificador = @"Hola, \""StackOverflow\""";

Console.WriteLine(sin_identificador); // Imprime Hola, "StackOverflow"
Console.WriteLine(con_identificador); // Imprime Hola, \"StackOverflow\"

    You can see more examples in the attached official documentation.

    • 9

  3. What is?

    $is a shortcut for String.Formatand is used with string interpolations.

    Using it on the string "hola"would not modify anything, just like using String.Format("hola"). Now in the case you show in your code:

    $"opcion1:{valorOpcion1}",
$"opcion1:{valorOpcion2}"

    What it does is put the values ​​of valorOpcion1y valorOpcion2, inside the string.

    • 5