Açıklanan C# IStructuralEquatable nerelerde kullanılıyor Hakkında 5 Kolay Gerçekler

Açıklanan C# IStructuralEquatable nerelerde kullanılıyor Hakkında 5 Kolay Gerçekler

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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?

In certain scenarios (such as using the value type kakım a key in a dictionary) it can murder performance in one foul swoop.

The following example creates two identical 3-tuple objects whose components consist of three Double values. The value of the second component is Double.NaN. The example then calls the Tuple.Equals method, and it calls the IStructuralEquatable.Equals method three times. The first time, it passes the default equality comparer that is returned by the EqualityComparer.

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Structural equality means that two objects are equal because they have equal values. It differs from reference equality, which indicates that two object references are equal because they reference the same physical object. The IStructuralEquatable interface enables you to implement customized comparisons to check for the structural equality of collection objects.

So, I am apparently wrong birli unequal objects may have equal hash codes. But isn't GetHashCode returning a somewhat randomly distributed takım of values a requirement?

I've noticed these two interfaces, and several associated classes, have been added in .NET 4. They seem a bit superfluous to me; I've read several blogs about them, but I still birey't figure out what sorun they solve that was tricky before .Kupkuru 4.

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 hamiş 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 bey, or follows another object in the sort order.

The example on MSDN gives part of the answer here; it seems to be useful for heterogeneous equality, rather than homogeneous equality - i.e. for testing whether two objects (/values) of potentially different types

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.

The Equals method supports custom structural comparison of array and tuple objects. This method in turn calls the comparer object's IEqualityComparer.Equals method to compare individual array elements or tuple components, starting with the first element or component.