Question

可悲地遭受大脑衰退。我有以下场景：

void Main()
{
    List<CaseBase> caseList = new List<UserQuery.CaseBase>();
    caseList.Add(new CaseBase() {CaseID = 1, CaseSequence = 1, CaseStatus = 1});
    caseList.Add(new CaseBase() {CaseID = 1, CaseSequence = 2, CaseStatus = 2});
    caseList.Add(new CaseBase() {CaseID = 2, CaseSequence = 1, CaseStatus = 1});

    var cases = caseList.Where(x => new List<int> {2}.Contains(x.CaseStatus));
    
}

// Define other methods and classes here
public class CaseBase
{ 
    public int CaseID {get;set;}
    public int CaseSequence {get;set;}
    public int CaseStatus {get;set;}
}

哪个返回预期

<头>

CaseID	案例序列	案例状态
1	2	2

我想要的是所有具有相同 ID 且其中一个状态为 2 的情况。

<头>

CaseID	案例序列	案例状态
1	1	1
1	2	2

这应该很简单，但我正在努力寻找一个简单的解决方案。

Answer 1

有几种方法可以继续：

您可以通过 CaseID 组合案例并选择匹配的组，然后将它们分开：

var cases = caseList
                .GroupBy(c => c.CaseID)
                .Where(cg => cg.Any(c => new List<int> { 2 }.Contains(c.CaseStatus)))
                .SelectMany(cg => cg);

您可以找到所需的CaseID，然后获取所有匹配的案例：

var wantedCaseIDs = caseList
                        .Where(c => new List<int> { 2 }.Contains(c.CaseStatus))
                        .Select(c => c.CaseID)
                        .ToHashSet();
var cases = caseList.Where(c => wantedCaseIDs.Contains(c.CaseID));

Answer 2

或者你可能想这样做：

void Main()
{
    List<CaseBase> caseList = new List<UserQuery.CaseBase>();
    caseList.Add(new CaseBase() { CaseID = 1, CaseSequence = 1, CaseStatus = 1 });
    caseList.Add(new CaseBase() { CaseID = 1, CaseSequence = 2, CaseStatus = 2 });
    caseList.Add(new CaseBase() { CaseID = 2, CaseSequence = 1, CaseStatus = 1 });
    
    var cases = caseList.Where(x => new List<int> { 2 }.Contains(x.CaseStatus))
        .Join(caseList,x => x.CaseID,y => y.CaseID,(x,y) => new {x,y})
        .Select(z => z.y)
        .Dump();

}

Linq 查询和潜在的自联接/分组依据

2 个答案: