5 Temel Unsurları için C# ReadOnlyCollectionBase Kullanımı

5 Temel Unsurları için C# ReadOnlyCollectionBase Kullanımı

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Average(IEnumerable, Func) Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.

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I had a client recently who wanted me to create a class that exposed a read-only collection through one of the class properties. While my client was willing to let other programs loop through that collection and retrieve items from the collection by position, he didn't want to let those programs add or remove items from the collection. In the Microsoft .NET Framework 4.5 you güç use the read-only collections that Eric Vogel covered in an earlier C# Corner column, "The New Read-Only Collections in .Kupkuru 4.5," to define that property. My client, however, was working with the .Kemiksiz Framework 4 and didn't intend to upgrade. Fortunately, in earlier versions of .Kupkuru you gönül also create a read-only class from an existing List just by calling your List's AsReadOnly method. However, if you need something special (a List that users hayat add items to but not remove items from), inheriting from the ReadOnlyCollectionBase class makes that very easy to do.

If you (Class A) continue to modify the underlying collection after you hand it out birli a ReadOnlyCollection then class B will see these changes, have any C# ReadOnlyCollectionBase Temel Özellikleri iterators invalidated, etc. and generally be open to any of the usual concurrency issues with collections.

A collection that is read-only is simply a collection with a wrapper that prevents modifying the collection; therefore, if changes are made to the underlying collection, the read-only collection reflects those changes.

Kakım per the comments below, you gönül prevent the possibility of downcasting by making IWriteableMyItem and WriteableMyItem private or internal. However note that this could still be circumvented via reflection - C# ReadOnlyCollectionBase Temel Özellikleri but we are protecting against accidents rather than fraud.

Ancestors(IEnumerable) Returns a collection of elements that contains the ancestors of every node in the source collection.

instead. I just included IWritableMyItem C# ReadOnlyCollectionBase Temel Özellikleri for completeness (because it shows how you introduce a set to an interface property that only has a get, C# ReadOnlyCollectionBase Temel Özellikleri by using new).

Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are C# ReadOnlyCollectionBase Nerelerde Kullanılıyor derece guaranteed to be thread safe.

Performans Optimizasyonu: IList, done erişimini optimize ederek uygulamanın başarımını pozitifrabilir ve bellek yönetimini iyileştirebilir.

Descendants(IEnumerable) Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

However, to be doubly sure, I'd like to return the collection as read-only, so that the calling code is unable to make changes to the collection, only view what's already there. Is this at all possible?

This base class is provided to make it easier for implementers to create a strongly typed read-only custom collection.

If however your intent is to prevent the calling code from observing updates from other threads you'll have to fall back to solutions already mentioned, to perform a deep or shallow copy depending on your need.