使用LINQ查找多个属性的重复项

Given a class with the following definition:

给定具有以下定义的类：

public class MyTestClass
{
    public int ValueA { get; set; }
    public int ValueB { get; set; }
}

How can duplicate values be found in a MyTestClass[] array?

如何在MyTestClass []数组中找到重复值？

For example,

例如，

MyTestClass[] items = new MyTestClass[3];
items[0] = new MyTestClass { ValueA = 1, ValueB = 1 };
items[1] = new MyTestClass { ValueA = 0, ValueB = 1 };
items[2] = new MyTestClass { ValueA = 1, ValueB = 1 };

Contains a duplicate as there are two MyTestClass objects where ValueA and ValueB both = 1

包含副本，因为有两个MyTestClass对象，其中ValueA和ValueB都= 1

3 个解决方案

#1

You can find your duplicates by grouping your elements by ValueA and ValueB. Do a count on them afterwards and you will find which ones are duplicates.

您可以通过ValueA和ValueB对元素进行分组来找到重复项。之后再计算它们，你会发现哪些是重复的。

This is how you would isolate the dupes :

这就是你如何孤立欺骗：

var duplicates = items.GroupBy(i => new {i.ValueA, i.ValueB})
  .Where(g => g.Count() > 1)
  .Select(g => g.Key);

#2

You could just use Jon Skeet's DistinctBy and Except together to find duplicates. See this Response for his explanation of DistinctBy.

您可以使用Jon Skeet的DistinctBy和Except一起查找重复项。有关他对DistinctBy的解释，请参阅此响应。

MyTestClass[] items = new MyTestClass[3];
items[0] = new MyTestClass { ValueA = 1, ValueB = 1 };
items[1] = new MyTestClass { ValueA = 0, ValueB = 1 };
items[2] = new MyTestClass { ValueA = 1, ValueB = 1 };

MyTestClass [] distinctItems = items.DistinctBy(p => new {p.ValueA, p.ValueB}).ToArray();
MyTestClass [] duplicates = items.Except(distinctItems).ToArray();

It will only return one item and not both duplicates however.

它只会返回一个项目而不是两个重复项目。

#3

MyTestClass should implement the Equals method.

MyTestClass应该实现Equals方法。

public bool Equals(MyTestClass x, MyTestClass y)
{
    if (Object.ReferenceEquals(x, y)) return true;

    if (Object.ReferenceEquals(x, null) ||
        Object.ReferenceEquals(y, null))
            return false;

        return x.ValueA == y.ValueA && y.ValueB == y.ValueB;
}

Here you have a good article about it.

在这里你有一篇很好的文章。

After that you can get a "clean" list of MyTestClass with "Distinct" method.

之后，您可以使用“Distinct”方法获取MyTestClass的“干净”列表。

#1