C# 用于比较具有复杂实体的两个列表的LINQ

我们的班级结构如下所示

public class ItemDTO
{
    public int ItemID { get; set; }
}


public class CostPageDTO
{
    public string CostPageNumber { get; set; }
    public List<ItemDTO> Items { get; set; }
}

---

这将选择您的预期结果：

方法语法：

var result = selectedCostPageAndItems.SelectMany(scp => actualItems.Where(acp=>acp.CostPageNumber == scp.CostPageNumber),
                            (scp,acp)=> new {CostPageNumber = scp.CostPageNumber,
                                        scpItems = new HashSet<int>(scp.Items.Select(x=>x.ItemID)),
                                        acpItems = new HashSet<int>(acp.Items.Select(x=>x.ItemID))})
                        .Where(x => x.scpItems.SetEquals(x.acpItems))
                        .Select(x => x.CostPageNumber);

var result = from cp1 in selectedCostPageAndItems
             from cp2 in actualItems
             let items1 = new HashSet<int>(cp1.Items.Select(x=>x.ItemID))
             let items2 = new HashSet<int>(cp2.Items.Select(x=>x.ItemID))
             where cp1.CostPageNumber == cp2.CostPageNumber
             && items1.SetEquals(items2)
             select cp1.CostPageNumber;

对于每一对（

scp

和

acp

），为所选（

scpItems

）和实际（

acpItems

）选择

CostPageNumber

和一组

ItemDTO.ItemID

）和

CostPageDTO

(scp,acp)=> new {CostPageNumber = scp.CostPageNumber,
                                    scpItems = new HashSet<int>(scp.Items.Select(x=>x.ItemID)),
                                    acpItems = new HashSet<int>(acp.Items.Select(x=>x.ItemID))})

创建和比较都是O（n）

selectedCostPageAndItems.SelectMany(scp => actualItems.Where(acp=>acp.CostPageNumber == scp.CostPageNumber)

(scp,acp)=> new {CostPageNumber = scp.CostPageNumber,
                                    scpItems = new HashSet<int>(scp.Items.Select(x=>x.ItemID)),
                                    acpItems = new HashSet<int>(acp.Items.Select(x=>x.ItemID))})

Where(x => x.scpItems.SetEquals(x.acpItems)).Select(x => x.CostPageNumber)