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Windows 10 icollections7/27/2023 ![]() ![]() They are merely exposing it via GetValueRefOrNullRef. (The AsSpan function is also potentially unsafe to use, as collection sizes cannot be modified while the Span exists.)Īnother is that the function already existed as the internal method Dictionary.FindValue. The developers feared it would be too easy to use incorrectly, so they intentionally wanted to make it hard to find. There are a few interesting facts about this function.įirst of all, it’s not an extension method. In order to offer the same capabilities for dictionaries, a new function called CollectionsMarshal.GetValueRefOrNullRef was created. NET 5, the CollectionsMarshal.AsSpan method makes it easy to get a span wrapper around a collection. This technique is used by the Span struct starting in. This allowed indexers to return a reference to a stuct rather than a copy. In C# 7, reference return values (ref returns) were introduced. Unlike the indexer property in a List, array elements are accessed directly. To avoid these unnecessary copies, mutable structs were usually stored in arrays. And since performance is often cited as the reason for using mutable structs in the first place, using copy-out/copy-in is counter-productive. For small structs this isn’t too bad, but can be expensive for larger ones. This can be difficult because it is easy to accidentally copy a mutable struct, resulting in two values that are no longer kept in sync.Ī work-around for this is to intentionally copy the struct, make the alterations, then copy it back into the original location. ![]() Though rare, occasionally developers need to work with mutable structs. So perhaps it’s time to offer a new alternative that doesn’t have the IList wrapping constructor and its associated problems. It also lacks the high performance, struct based IEnumerator that List offers. The lack of an AddRange method has long annoyed developers. This isn’t the only design flaw in Collection and ObservableCollection. As a subclass of Collection, ObservableCollection cannot expose an EnsureCapacity method either. Unlike the others, Collection may optionally wrap another collection which may not necessarily expose an EnsureCapacity method. The EnsureCapacity method has been added to the List, Stack, and Queue classes so they too can gain the performance benefit.Ī notable exclusion from this group is Collection. This allows the collection to perform one resize operation upfront, avoiding the possibility of multiple resizes being needed. NET 6, we look at collections.īefore performing a large set of inserts into a Dictionary or HashSet, it is helpful to call EnsureCapacity with the expected collection size. Next in our series on the API changes for. ![]()
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