C＃类实例比较，截然不同 [英] C# class instance comparison, distinct

问题描述

Hello Guys，

我想知道是否有人知道更好的方法来获得与List< some_class>的区别没有使用任何助手类。



目前我有这个（我简化了这个）：

Hello Guys,
I was wondering if anyone knows a better way to get a distinct from List<some_class> not using any helper classes.

Currently I have this (I have simplified this):

class A
{
int X, Y;
public A(int xx, int yy)
{ X = xx; Y = yy;}
}

//this is a helper class I want to get rid of
class helper : IEqualityComparer<A>
{
public bool Equals(A x, A y)
{return x.X == y.X && x.Y == y.Y;}

public int GetHashCode(A obj)
{return 0;}
}

List<A> class_array = new List<A>
class_array.Add(new A(1, 1));
class_array.Add(new A(1, 1));
class_array.Add(new A(2, 2));
class_array.Add(new A(2, 2));

class_array = class_array.Distinct(new helper()).ToList()

任何人都知道更好的解决方案吗？我需要这个的原因是我有多个类数组要比较，我真的不希望每个都有帮助比较类...这听起来不对...



提前谢谢！

Anyone know a better solution for the situation? The reason I need this is that I have multiple class arrays to compare and I dont really want to have helper comparison classes for each... This just does not sound right...

Thank you in advance!

推荐答案

来自文档 [ ^ ]：



默认的相等比较器Default用于比较值实现 IEquatable< t> [ ^ ]通用界面。要比较自定义数据类型，您需要实现此接口并为该类型提供自己的GetHashCode和Equals方法。



所以类 A 需要实现此界面。





-Edit-

这对我来说很好：

From the documentation[^]:

The default equality comparer, Default, is used to compare values of the types that implement the IEquatable<t>[^] generic interface. To compare a custom data type, you need to implement this interface and provide your own GetHashCode and Equals methods for the type.

So class A would need to implement this interface.


-Edit-
This works fine for me:

class A : IEquatable<A>
{
	int X, Y;
 
	public A(int xx, int yy) { X = xx; Y = yy; }	
	public override bool Equals(object other) { return Equals((A)other); }	 // Note that this implementation doesn't follow proper standards. Always check for null values, or objects of a different type and handle them accordingly.
	public bool Equals(A other) { return X == other.X && Y == other.Y; }	
	public override int GetHashCode() { return (X + Y).GetHashCode(); }
}

尝试如下。



注意： 我没有测试。请检查。

Try is as below.

Note:I didn't test.Please check that.

List<A> distinct =
  class_array
  .GroupBy(a => new {a.X,a.Y})
  .Select(g => g.First())
  .ToList();

仅用于变化：

List<A> ADeDupe = class_array
    .Select(a => new {X = a.X, Y = a.Y})
        .Distinct()
            .ToList()
                .Select(a => new A(a.X, a.Y))
                    .ToList();

imho，如果实现自定义Comparer，将来您的代码将更易于维护，并简单地使用'Distinct，而不是使用棘手的Linq。

imho, your code will be more maintainable in the future if you implement the custom Comparer, and simply use 'Distinct, rather than using "tricky" Linq.

这篇关于C＃类实例比较，截然不同的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！