How can I use escape characters with string interpolation in C# 6?

Question

I've been using string interpolation and love it. However, I have an issue where I am trying to include a backslash in my output, but I am not able to get it to work.

I want something like this...

var domain = "mydomain";
var userName = "myUserName";
var combo = $"{domain}\{userName}"

I want the output of combo to be:

myDomain\myUserName

I get a syntax error about the \ being an escape character. If I put in \\ then the syntax error is gone, but the output is myDomain\\myUsername.

How can I include escaped characters in an interpolated string?

Heracliteanism

Thanks. But then I cant use string interpolation? I don't want to escape everything. I just want to use a backslash inside of an interpolated string. – Heracliteanism

No you can't. His answer is wrong. – Pneumodynamics

feels like a bug to me ;) \\ should work – Heracliteanism

I get the correct output for ${domain}\\{userName}.. Is it a web application? – Pneumodynamics

you mean something like string.format("{0}\\{1}", domain, userName); or string.format(@"{0}\{1}", domain, userName); – Perdita

console app. Console.WriteLine($"{DateTime.Now.ToString("dd/MM/yyyy hh:mm:ss")} Writing record for {domainstring}\\{UserName}" ); – Heracliteanism

@ДмитрийЧистик Yes he is using the short version of string interpolation.. I don't know why yours doesn't work, I exactly did the same in my console application and it works. – Pneumodynamics

I don't want to use string.format I want to use the new string interpolation feature of c# 6. Notice in my code I don't have any value place holders in the curly braces or variables after the string. the values are essentially interpolated on the fly in c# 6 – Heracliteanism

String interpolation should work for `\`. That's how you escape a single backslash. – Florafloral

Nhan's answer seems to work perfectly. $@"{domain}\{userName}". I think you should try it, and accept it. I had exactly the same problem, down to it also being domain and user name, and his method works fine. – Gaskill

any update here for c# 8.0 ? – Chigger

Answer 1

Escaping with a backslash(\) works for all characters except a curly brace.

If you are trying to escape a curly brace ({ or }), you must use {{ or }} per $ - string interpolation (C# reference)

... All occurrences of double curly braces (“{{“ and “}}”) are converted to a single curly brace.

Birthstone

It doesn't work for a backslash itself, as the OP clearly explains. – Gaskill

This is the answer - why isn't it flagged yet? Shouldn't it be? – Anteroom

Answer 2

You can do this, using both the $@. The order is important.

var combo = $@"{domain}\{userName}";

The original question mentions specifically C# 6. As commented, C# 8 no longer cares for the order.

Okoka

The best and simple answer. Don't understand why people choose more complicated answers. MSDN link for verbatim interpolated strings learn.microsoft.com/en-us/dotnet/csharp/tutorials/… – Moritz

"Starting with C# 8.0, you can use the $ and @ tokens in any order" (From Alex's link in the above comment). – Mosier

Answer 3

Eduardo is correct. You escape curly braces by doubling up. Therefore, if you wanted to output the domain variable as {mydomain} you would need to do:

$"{{{domain}}}";

Furthermore, assuming that the current date is 1 Sept 2016, doing this:

$"The date is {DateTime.Now}";

would output something like "The date is 2016/09/01 3:04:48 PM" depending on your localization. You can also format the date by doing:

$"The date is {DateTime.Now : MMMM dd, yyyy}";

which would output "The date is September 1, 2016". Interpolated strings are much more readable. Good answer Eduardo.

Material

The OP isn't trying to escape curly braces. They clearly state they are trying to escape a backslash itself, and the normal `\\` doesn't work in an interpolated string. – Gaskill

I don't care what OP was asking I wanted to escape curly braces and first google entry was this. So OP heading mislead google and this is therefore a valid answer and deserves upvoting. – Caco

Answer 4

$"{domain}\\{user}"

Works fine - escaping works as usual (except when escaping {). At least on .NET 4.6 and Visual Studio 14.0.22823 D14REL.

If it doesn't work for some reason (maybe you're using an older version of the compiler?), you could also try being more explicit:

$"{domain}{@"\"}{user}"

Lockard

That's what I thought too. interesting, on my surface pro 3, the code works fine with either the normal \\ or explicit @"\", however on my work machine it does not. so I think you may have hit the nail on the head with regards to the version installed. My work machine is saying no updates are available, unfortunately. So, my question to you is how do I determine the exact version/build of .net 4.6 on my machine? things seem to have changed a bit in this regard an im not able to find much guidance on build/version numbers. – Heracliteanism

from what I can tell I am running the same version of .net and vs 2015 RC on both machines. the only difference I can think of is that the machine that is working as expected (SP3) is running the latest insider preview of windows 10. I believe .net framework comes with this, so maybe I have a newer version there somehow. I just don't know how to check specifically though. – Heracliteanism

UPDATE looking in the c:\windows\microsoft.net\framework64\v4.0.30319 folder at the property details for clr.dll I can see a difference. the version on my surface is 4.6.79.0 and the version on my work machine is 4.6.57.0. So my question is now, how do I upgrade from 4.6.57.0 to 4.6.79.0? (why is this sooo hard! ;) – Heracliteanism

@Heracliteanism I don't think that's it - I also have 4.6.57.0 and it works fine. Is it possible you have some Visual Studio extension installed that messes things up? – Lockard

In case you observe a difference in behavior despite not seeing any updates perhaps consider the use of the NuGet package "Microsoft.Net.Compilers" in the projects that use the latest C# features. This may resolve the observed differences in behavior. It did in our projects. – Wilhelmstrasse

Answer 5

The rule for escape the backslash in an interpolated string is to duplicate the backslash:

var domain = "mydomain";
var userName = "myUserName";
var combo = $"{domain}\\{userName}";

But if you also use the interpolated string as a verbatim string then you don't need to escape the backslash:

var domain = "mydomain";
var userName = "myUserName";
var combo = $@"{domain}\{userName}";

And you get the same:

For a tutorial about interpolated strings (in Spanish): see a video about interpolated strings

Sunderance

The referenced video is in Spanish. – Entrails

Here you go, the complete Serie in English: youtube.com/playlist?list=PL9B-92Xt-uA6tVNtz7Gd9h900R1_eJkRz – Sunderance

Answer 6

If I did not misunderstand, the solution is real simple:

var domain = "mydomain";
var userName = "myUserName";
var combo = $"{{{domain}}}\\{{{userName}}}";
Console.WriteLine(combo);

I share birdamongmen's answer as well as the good reference provided there.

Lilliamlillian

You did misunderstand. The OP isn't trying to escape curly braces. They clearly state they are trying to escape a backslash itself, and the normal `\\` doesn't work in an interpolated string – Gaskill

Answer 7

You can use this -

' First, declare the curly brackets as chars
Dim LeftBrace As Char = "{"
Dim RightBrace As Char = "}"

' Then in your string, use it like this:
Dim myStr As String = $"This is a {LeftBrace}String{RightBrace}"

' Now, the output will be
' This is a {string}code here

Nagoya

This is no C#? (but VB.NET?) – Gwenora

Well, this is the same feeling when a vb .net programmer get a c# answer for his question. – Nagoya