Docs: What is $"

[Vespiyanus]

For newbies, It would be very nice to see some explanations or note on $" (in Performing Operations on Source Elements section)

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Document Details

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• ID: b4a44517-d9a2-454d-90f3-90d9553ff4be
• Version Independent ID: f31a6959-8212-a49f-eeb4-43936dbfbadb
• Content: Data Transformations with LINQ (C#)
• Content Source: docs/csharp/programming-guide/concepts/linq/data-transformations-with-linq.md
• Product: dotnet-csharp
• Technology: csharp-linq
• GitHub Login: @BillWagner
• Microsoft Alias: wiwagn

[IEvangelist]

Hi @Vespiyanus, thank you for raising this concern. Yes, I can see how it might be confusing to newbies. All of a sudden new and unfamiliar syntax is being used without any details about its usage.

I've added the "up-for-grabs" label on this issue, so that anyone could work on it before we have a chance to. To answer the ask, the $" is used for formatting strings, and is called string interpolation.

What it does, is format expressions within the string. It tells the C# compiler that the string should evaluate the expressions and then concatenate the pieces together.

double[] radii = { 1, 2, 3 };

IEnumerable<string> query =
    from rad in radii
    select $"Area = {rad * rad * Math.PI:F2}";

This is essentially shorthand for this "Area = " + (rad * rad * Math.PI).ToString("F2")

The query could then be iterated on, and it's just a string collection with the following values:

"Area = 3.14",
"Area = 12.57",
"Area = 28.27"

[jmarkman]

I'd like to take a crack at refactoring this particular section to provide a bit more clarity for newer readers, if that's alright.

[IEvangelist]

Hi @jmarkman - absolutely. Thank you