比较两份名单通过一个物业使用LINQ [英] Compare Two Lists Via One Property Using LINQ

问题描述

说我有以下几点：

    class Widget1{
        public int TypeID { get; set; }
        public string Color { get; set; }
    }

    class Widget2
    {
        public int TypeID { get; set; }
        public string Brand { get; set; }
    }

    private void test()
    {
        List<Widget1> widgets1 = new List<Widget1>();
        List<Widget2> widgets2 = new List<Widget2>();
        List<Widget1> widgets1_in_widgets2 = new List<Widget1>();

        //some code here to populate widgets1 and widgets2

        foreach (Widget1 w1 in widgets1)
        {
            foreach (Widget2 w2 in widgets2)
            {
                if (w1.TypeID == w2.TypeID)
                {
                    widgets1_in_widgets2.Add(w1);
                }
            }
        }
    }

我我使用两个foreach循环由TYPEID的名单相比较来填充第三个列表。
是否有使用LINQ to通过TYPEID这两个列表比较任何其他方式？也许使用Interstect或其他一些功能？

I am using two foreach loops to compare the lists by TypeID to populate a third list. Is there any other way using LINQ to compare these two lists via the TypeID? Perhaps using Interstect or some other function?

推荐答案

您想在这里什么是加入。

var widgets1_in_widgets2 = from first in widgest1
    join second in widgets2
    on first.TypeID equals second.TypeID
    select first;

相交可以是更多或想象的那样作为一个特例加入其中两个序列是相同类型的，并且因此可以应用于平等代替需要一个突起的每种类型，以产生一个关键来比较。鉴于你的情况下，相交不是一个选项。

Intersect can be more or less thought of as a special case of Join where the two sequences are of the same type, and can thus be applied for equality instead of needing a projection for each type to generate a key to compare. Given your case, Intersect isn't an option.

如果一个特定的ID在你的第二组和复制你不想要的项目在结果被复制，那么你可以使用，而不是一个群组加入 A 加入：

If a particular ID is duplicated in your second set and you don't want the item to be duplicated in the results then you can use a GroupJoin instead of a Join:

var widgets1_in_widgets2 = from first in widgest1
    join second in widgets2
    on first.TypeID equals second.TypeID
    into matches
    where matches.Any()
    select first;

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