I'm confused as to why this code won't compile:
var result = $"{fieldName}{isDescending ? " desc" : string.Empty}";
If I split it up, it works fine:
var desc = isDescending ? " desc" : string.Empty;
var result = $"{fieldName}{desc}";
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11@Sinatr Updated link: thebillwagner.com/Blog/Item/…Nate Barbettini– Nate Barbettini2015-10-06 13:48:41 +00:00Commented Oct 6, 2015 at 13:48
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The same applies to the namespace alias qualifier (::).Uwe Keim– Uwe Keim2016-05-11 08:32:55 +00:00Commented May 11, 2016 at 8:32
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Roslyn team related discussion: Strange syntax error in interpolated string when using ?:mins– mins2020-04-30 13:41:20 +00:00Commented Apr 30, 2020 at 13:41
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1 Answer
According to the documentation:
The structure of an interpolated string is as follows:
{ <interpolationExpression>[,<alignment>][:<formatString>] }
The problem is that the colon is used to denote formatting, like:
Console.WriteLine($"The current hour is {hours:hh}")
The solution is to wrap the conditional in parenthesis:
var result = $"Descending {(isDescending ? "yes" : "no")}";
4 Comments
Jan
Even more interesting example is this one when you need to use a nested interpolation string:
Console.WriteLine($"Cargo Weight: {(ship.WeightAvailable ? $"{ship.Weight:0.00}" : "n/a")}");Guilherme Flores
another example, ternary if with string interpolation in the condition: var foo = $"{x.Title} {(!string.IsNullOrEmpty(x.SubTitle) ? $"({x.SubTitle})" : string.Empty)}";
MgSam
@Jan And yet even the example you give doesn't compile, and yet ReSharper has no problem disambiguating it (since it knows to offer a code fix).
Jan
@MgSam It would help if you tell the error and your development setup. I tested my example again (copy/paste it) using VS2019 and VS2022 using .NET Core 2 till .NET Core 6 and also .NET 2 to .NET 4.8. All compiled fine (if you have a
Ship class with a bool WeighAvailable and double Weight public properties/attributes of course).