and get a grup of actors with unique last names. So we need a way to provide a key selector to our ActorComparer. This is done simply by creating a constructor that takes a function object kakım an argument and stores it for further use:
This is used for custom sorting of objects. Prior to .Kemiksiz 3.5 it was used primarily for Array.Sort but now finds itself used for sorting with LINQ.
The CompareTo method would be the default way of ordering your User class, perhaps comparing by Name. If you then decided that you wanted to sort a list of User objects by another property, say Age, you could write a class that implemented IComparer instead of altering CompareTo inside User. This would perform the custom sorting, for example:
Make the properties / fieldInfos fields static; they don't change for each closed instance of the type PropertiesByValueComparer (i.e., for each T passed to it), so you don't need to initialize them for every new instance of the comparer
EDIT: Birli you´ve mentioned ReSharper, I assume kakım you provide the actual properties to be validated at runtime even R# doesn´t know a good way to implement GetHashCode.
This is because LINQ methods accept IEnumerable kakım a parameter. Consequently, they have no concept of the implementation of the original list.
Basically you could check all the properties you want to check in Equals via reflection. To filter some of C# IEqualityComparer nerelerde kullanılıyor them out use an attribute on those properties:
If you look at the definition of Distinct there is only one generic type parameter involved (and not one TCollection used for input and output C# IEqualityComparer Kullanımı collections and one TComparison for the comparer).
There are many C# IEqualityComparer nerelerde kullanılıyor cases where one might want to have a Dictionary locate objects using something other than 100% equivalence. As a simple example, one may wish to have a dictionary which matches in case-insensitive fashion. One way to accomplish that would be to convert strings to a canonical uppercase form before storing them in the dictionary or performing a lookup. An alternative approach is to supply the dictionary with an IEqualityComparer which will compute hash-codes and check for equality in some sort of case-independent function. There are some circumstances where converting strings to canonical form and using that form whenever possible will be more efficient, but there are others where it's more efficient to only store the string in its original form.
If it is possible, emanet we add an attribute to a property to say that this property is not relevant in the comparison?
Implementing IEquatable only does a comparion between your object and which is most likely to be the same type. This is performed frequently with the new methods brought in alongside LINQ in 3.5. Overriding Equals() from ValueType will do a check for any object type, and it’s recommended this is overridden with any C# IEqualityComparer nedir custom value type alongside implementing IEquatable.
According to this thinking, both types should implement IEquatable, because it doesn't seem likely that there are other meaningful ways of doing an equality test.
What Distinct() actually does here is comparing object references. So our second George Clooney is in fact an independent object (since it was created C# IEqualityComparer Nasıl Kullanılır independently) and its reference differs from the reference of the first one - therefore it appears in the output twice:
If there are multiple ways instances of a class could be considered equal. The best example of this is a string, for which the framework provides six different comparers in StringComparer.