合并两个不同类型的列表 [英] Merge two Lists of different types

问题描述

我将数据从另一个列表添加到列表的对象中:

I add data to the objects of a List from another List:

public void MergeLsts(List<A> lstA, List<B> lstB)
{
    foreach (A dataA in lstA)
    {
        foreach (B dataB in lstB)
        {
            if (dataA.ItemNo == dataB.ItemNo)
            {
                //dataA.ItemDescription is up to this point empty!
                dataA.ItemDescription = dataB.ItemDescription;
            }
        }
    }
    DoSomethingWithTheNewLst(lstA);
}

这很好用.但是，这需要花费很长时间，因为两个列表都变得非常大(在lstA中大约为70k，在lstB中为大约2000k).

This works perfectly fine. However it takes pretty long because both lists get quite large (around 70k items in lstA and 20k items in lstB).

我想知道是否有更快或更有效的方式来完成我所需要的?也许使用LINQ?

I was wondering if there is a faster or more efficient way to accomplish what I need? Maybe with LINQ?

推荐答案

您可以使用O(n)复杂度来代替O(N²)使用Join():

You can do it with O(n) complexity instead of O(N²) with Join():

var joinedData =  dataA.Join(dataB, dA => dA.ItemNo, dB => dB.ItemNo, (dA, dB) => new { dA, dB }));
foreach(var pair in joinedData)
{
    pair.dA.ItemDescription = pair.dB.ItemDescription;
}

Distinct，GroupBy和Join操作使用哈希，因此它们应靠近O(N)而不是O(N²).

Distinct, GroupBy and Join operations use hashing, so they should be close to O(N) instead of O(N²).

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