Code & Sundry

Jon G Stødle

The underrated new[] { } in C#

340 words, 2 minutes to read

17 years into it's life, C# has a lot of language features. This means that some of them are likely to go unnoticed by some people, maybe even a lot of people.

A feature which isn't get the love I think it deserves is implicitly typed arrays, or the new[] { } syntax. It's a shorthand for writing arrays. The type of the array is inferred from the contents you give it:

var a = new[] { 1, 10, 100, 1000 }; // int[]
var b = new[] { "hello", null, "world" }; // string[]

"That's nice and all", you might think. "But who uses arrays in C# these days?". While it's true there are a lot of other types of collections in .Net which are far better for a lot of use cases, I think implicitly typed arrays still has a very nice use case.

Creating arrays in this manner is only useful when you know the elements you want to put into it. This means it's great for passing a few values together. It becomes infinitely more useful when you realize that arrays implement IList<T>.

For any method that takes an IEnumerable<T> or IList<T> as a parameter you can pass an implicit array if you only have a small set of values to pass:

GiveMeAnIEnumerableOfString(new[] { "Ten", "Eleven", "Twelve", "Nine" });

It's also quite handy when you're writing a method which should return an IEnumrable<T> or IList<T>:

public IEnumerable<string> GetFourSpecificNames() => new[] { "Martha", "Rory", "Bill", "Rose" };

Which I prefer to this:

public IEnumerable<string> GetFourSpecificNames() => new List<string> { "Martha", "Rory", "Bill", "Rose" };

I prefer it to be implicit, just like I prefer to use the var keyword when creating local variables.


Which I think looks better than this:

public IEnumerable<string> GetFourSpecificNames()
    var list = new List<string>();
    return list;

Lately I've found myself using this syntax a lot when I need to pass a collection of known items.

Happy coding!