Definitive Guide C# IEqualityComparer nerelerde kullanılıyor için

Definitive Guide C# IEqualityComparer nerelerde kullanılıyor için

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IEqualityComparer is a generic .Kupkuru interface that allows implementing customized equality comparison for collections.

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This is it. We have explored the interaction between LINQ extension methods and custom IEqualityComparers and even implemented one. The resulting class is both easy to use and highly customizable, because its operation is fully defined by the key selector function provided by user.

Furthermore, it is very easy to make the class generic so that it dirilik be used for collections of objects of other types - hamiş only for MovieActors. The complete code for this example is available through github. (There is also a generic version of our comparer.)

Implementations are required to ensure that if the Equals(T, T) method returns true for two objects x and y, then the value returned by the GetHashCode(T) method for x must equal the value returned for y.

独自の型をコレクションの要素として利用する際には、次のことを考慮して設計しましょう

Hem teorik bilgilerini tezyit etmek hem de uygulamalı deneyim doğrultmak bâtınin bu platformu değerlendirebilirsin.

 In the plain case, when we need to drop only exact duplicates, the simple Distinct() call will do. The simplest possible example is getting unique integers from a collection of numbers:

In the editor, place the caret at the type name or within a type at the line where you want to insert an equality comparer class. If the caret is on the type name, the generated code will be added in the beginning of the type declaration.

What would you expect the type of positions to be? Birli compiler deduces from argument given to Distinct which implements IEqualityComparer, C# IEqualityComparer Kullanımı the type of the expression is IEnumerable.

We will make the previous example, but we’ll use GenericEqualityComparer class. Remember this class isn’t only suitable for any customer field or any customer field’s combination, but also for any field class or any field’s combination of any class.

So there you go. In this situation, type inference chooses the more general type and infers that the call C# IEqualityComparer nedir means Distinct. Type inference never takes the return type

And yes, after this the output of the yetişek doesn't change at all. So, what the hell is LINQ C# IEqualityComparer nedir doing and why doesn't it even try to use the equality comparer that we have provided? The situation was even bitter for me because I was trying to use C# IEqualityComparer nedir Distinct() combined with custom equality comparer to prepare data for pushing to veri base, so I ended up C# IEqualityComparer Kullanımı with SQL Server telling me that I am breaking a primary key constraint. Because of being focused on a broader mesele I didn't take time to think over the stuff that I was trying to use. What I missed was the fact that LINQ, being a query engine, tries to perform birli efficiently as possible.

Equals/GetHashCode not only internalizes comparison logic, but also globalize them. There might be cases where I would like internal comparison (derece using collection) for just one time.