Greatest Kılavuzu C# IStructuralEquatable Kullanımı için

Greatest Kılavuzu C# IStructuralEquatable Kullanımı için

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It's normally expected that if you implement IEquatable.Equals you will also override Object.Equals to be consistent. In this case how would you support both reference and structural equality?

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. The best example of this is arrays, which with .NET 4 now implement the IStructuralEquatable interface. This makes it possible to distinguish whether you are comparing two arrays for reference equality, or for "structural equality" - whether they have the same number of items with the same values in each position. Here's an example:

Equals and object.ReferenceEquals. Equals is meant to be overridden for whatever sort of comparison makes the most sense for a given type, whereas ReferenceEquals yaşama't be overridden and always compares by reference.

You generic method özgü 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 can use .Kemiksiz 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 C# IStructuralEquatable Nasıl kullanılır array or tuple to an IStructuralEquatable interface value and providing your IEqualityComparer implementation kakım an argument to the Equals method, you dirilik define a custom equality comparison for the array or collection.

What does IEquatable buy you, exactly? The only reason I dirilik see it being useful is when creating a generic type and forcing users to implement and write a good equals method.

This is very disappointing behaviour from Microsoft; I'm now wondering if I should review the list of cases I've filed and see if other ones I've submitted have been removed...

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 a memory comparison may derece give you the correct results in this super simple example:

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C# IStructuralComparable Determines whether the current collection object precedes, occurs in the same position birli, or follows another object in the sort order.

IStructuralEquatable is used with arrays to determine whether the arrays are structurally equal. The StructuralEqualityComparer.Equals method is used for this purpose.

You observations does not conflict with the documentation and there is no bug in the implementation.

However, this is not so great if you are using the struct in a dictionary birli my good friend Dustin mentioned to me because a Dictionary will always use the object version of Equals, which falls back to boxing :(