如何在给定属性上合并两个列表 [英] How to merge two lists on a given property

问题描述

我有两个查询，每个查询返回一个对象列表.

I have two queries, each one returning a list of objects.

List<A> list1 = (....query...)
List<A> list2 = (....query...)

"A"是一个对象模型.

"A" is an object model.

两个查询都返回几乎相同的对象，但设置了不同的属性.

Both queries return almost the same objects but with different properties set.

我要删除重复项，并根据对象A的属性将其合并为一个列表.

I want to remove duplicates merge them into a single list based on a property of object A.

基本上是这样的:

List<A> finalLis = list1 join list2 on elemList1.somePropID == elemList2.somePropID 

在简单的C#风格中，将是这样的:

In simple C# style it would be something like this:

foreach(elem1 : list1) {
    foreach(elem2: list1) {
       if(elem1.someID == elem2.someID) {
           elem1.someProp = elem2.someProp
           elem1.otherProp = elem2.otherProp
        }
     }
}

我不想这样做，因为我确信linq中有一种更优雅的方法.

I don't want to do it in this way because I'm sure there's a more elegant way in linq.

如果您有任何建议，请告诉我.

If you have any suggestions please let me know.

推荐答案

Linq可以帮助您进行选择，但不能帮助您进行更新.因此，您不会摆脱foreach语句.因此，您的任务可以像这样用linq编写:

Linq can help you with selecting but not with updating. So you won't get rid of foreach statement. So your task could be written with linq like this:

//the query is like LEFT JOIN in SQL
var query = from x in list1
            join y in list2 on x.IDItem equals y.IDItem
            into z
            from q in z.DefaultIfEmpty()
            select new {IOne = x, ITwo = q};
foreach (var pair in query)
{
    if (pair.ITwo != null) // && pair.IOne.OneProperty != null
        pair.IOne.OneProperty = pair.ITwo.TwoProperty;
}

var resultList = query.Select(x => x.IOne).ToList();

您可以在此处查看结果.

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