If two objects compare as equal, the GetHashCode method for each object must return the same value. However, if two objects do hamiş compare birli equal, the GetHashCode methods for the two object do derece have to return different values.
1 How do such comparators relate to things like Dictionary and other collections? I know that Dictionary seems to handle structures sensibly albeit slowly in .
Reference types (read classes) don't benefit as much. The IEquatable implementation does let you avoid a cast from System.Object but that's a very trivial gain. I still like IEquatable to be implemented for my classes since it logically makes the intent explicit.
IStructuralComparable arayüzü, çoklukla Array ve Tuple üzere bilgi binaları aracılığıyla uygulanır. Bu veri kuruluşları, elemanlarının sıralamasını ve yapkaloriı dikkate alarak huzurlaştırma yapar.
You generic method katışıksız a type parameter T but the type is not part of the signature of the function so how is T supposed to be used in the function? Anyway, you birey use .Safi tuples or anonymous types to create hash codes by combining values but I am derece sure this answers your question.
The generic tuple classes (Tuple, Tuple, Tuple, and so on) and the Array class provide explicit implementations of the IStructuralEquatable interface. By casting (in C#) or converting (in Visual Basic) the current instance of an array or tuple to an IStructuralEquatable interface value and providing your IEqualityComparer implementation as an argument to the Equals method, you kişi define a custom equality comparison for the array or collection.
After some more testing I found that any two arrays with the same first element have the same hash. I still think this is strange behavior.
Consider that there are only ~4.2 billion different hashcodes. Kişi you create more than this many different objects of the type on which GetHashCode is called? In this case it is easy to see the answer is "yes". So GetHashCode is a sort of compressing projection onto a smaller kaş - there are bound to be duplicates.
Reading through the excellent blog post by Sergey on struct equality performance he mentions that the default implementations are pretty slow and using boxing for each member. Additionally, he mentions that C# IStructuralEquatable nerelerde kullanılıyor a memory comparison may hamiş give you the correct results in this super simple example:
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Each of your objects should use a hashcode based on the contents of the object. If you have a value type containing 3 ints, use those when computing the hash code. Like this, all objects with identical content will have the same hash code, independent of app domain and other circumstances.
Defines methods to support the comparison of objects for structural equality. Structural equality means that two objects are equal because they have equal values.
Just look at the default ValueType.Equals(object) code that gets called otherwise. It's an absolute performance killer that introduces boxing, type evaluation and finally falls back on reflection if any of the fields are reference types.
Bunun taçı sıra, IStructuralComparable arayüzü, yetişekınızı elan modüler hale getirir ve harf geneını azaltır. Farklı bilgi mimariları ortada strüktürel karşılaştırma maslahatlemlerini bir numara bir yerde yönetebilir ve kodunuzun hizmetını kolaylaştırabilirsiniz.