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Switch expression for void methods

While preparing yesterday’s post, I was wondering if I could rewrite the following switch statement to use the new .NET 8 switch expression syntax.

Here is the original code:

And here is my attempt to rewrite this to a switch expression:

Unfortunately this didn’t work and resulted in a compiler error:

Only assignment, call, increment, decrement, await and new object expressions can be used as a statement.

Turns out that switch expression cannot return void. It must return a value and this value must be consumed and cannot be discarded. Too bad!

Maybe this is something that will change in future .NET versions as hinted here:

The switch_expression is not permitted as an expression_statement.

We are looking at relaxing this in a future revision.

More information

Recursive pattern matching - C# feature specifications | Microsoft Learn

switch expression - Evaluate a pattern match expression using the `switch` expression - C# | Microsoft Learn

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