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Ternary conditional operator

As explained in .NET in Action, Second Edition

A ternary operator is a conditional C# operator that evaluates a Boolean expression and selects one of two value expressions.

A ternary operator evaluates a Boolean expression and selects one of two values. Its compact form is <boolean expression> ? <true value> : <false value>. section 3.1.2

Selecting an HTTP result

When AsciiArt.Write returns a Boolean and both branches produce IResult values, the operator expresses success or failure directly: AsciiArt.Write(text, out var asciiText, font) ? Results.Content(asciiText!) : Results.NotFound(); The true expression returns generated content; the false expression returns HTTP 404. section 3.1.2

Listing 3.16 Returning 404 if font is invalid
app.MapGet("/{text}",
  (string text, string? font) =>
    AsciiArt.Write(text, out var asciiText, font)    #1
      ? Results.Content(asciiText!)                  #2
      : Results.NotFound());                         #3

Inspect the focused minimal-API listing showing a ternary expression selecting between Results.Content and Results.NotFound. section 3.1.2

How .NET in Action, Second Edition covers it

How deep it goes
Defines the three-part syntax and demonstrates equivalent if/else behavior, without expanding into broader operator semantics.
Examples
Demonstrates AsciiArt.Write selecting Results.Content for success and Results.NotFound for an invalid font.
What you can do after
Apply it in C# endpoints to express compact success-or-failure value selection.
How it connects
Connects Boolean expressions, if/else statements, out parameters, and ASP.NET Core IResult responses.
Cover of .NET in Action, Second Edition
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This explainer was generated by Manning's knowledge graph from the text of .NET in Action, Second Edition. The section links point to the parts of the book it draws on.