C# 12 features: Default lambda parameters

Part 4 in a series on new language features in C# 12.

Default lambda parameters

A pretty simple addition to the language - you can now provide default values for lambda expression parameters.

var IncrementBy = (int source, int increment = 1) => source + increment;

In the lambda defined above, if you don't supply the increment parameter, it defaults to 1.

Again, interesting, but I've not come across a need to use this yet.

Further reading

https://learn.microsoft.com/dotnet/csharp/language-reference/operators/lambda-expressions?WT.mc_id=DOP-MVP-5001655#input-parameters-of-a-lambda-expression

Example source

https://github.com/flcdrg/csharp-12/blob/main/04-optional-params-lambda/LambdaParameters.cs

C# 12 features: ref readonly

Part 3 in a series on new language features in C# 12.

ref readonly modifier

A bit more of a niche feature - if you have code that is passing structs by ref, but you don't need to (or want to) allow modification of the parameter, you can now indicate it is readonly.

    public static void ByRefReadonly(ref readonly Point p)
    {
        //p = new Point(2, 3);
        Console.WriteLine(p);

    }

In the code sample above, Point is a struct or record type. If you uncommented the line then the compiler will emit an error.

Interesting, but I've not come across a need to use this yet.

Further reading

https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/method-parameters?WT.mc_id=DOP-MVP-5001655#ref-readonly-modifier

Example source

https://github.com/flcdrg/csharp-12/blob/main/02-collection-expressions/CollectionExpressions.cs

C# 12 features: Collection expressions

Part 2 in a series on new language features in C# 12.

Collection expressions

You can now use square brackets [] to initialise a collection! Usually square brackets indicate an array, but the collection expression can be assigned to other collection types too.

You can use them to assign values to fields or in method bodies.

private List<int> numbersList = [1, 2, 3, 4, 5];

Like primary constructors, I've also found these quite useful in new .NET 8 projects.

Further reading

https://learn.microsoft.com/dotnet/csharp/language-reference/operators/collection-expressions?WT.mc_id=DOP-MVP-5001655

Example source

https://github.com/flcdrg/csharp-12/blob/main/02-collection-expressions/CollectionExpressions.cs