c# - Linq Group 结果到对象

Question

概览

当我上课时

public class RequestEntry
{
    public int RequestId
    {
        get;
        set;
    }

    public string ApproverUserId
    {
        get;
        set;
    }

    public string ApproverUserName
    {
        get;
        set;
    }

    public DateTime RequestedDate
    {
        get;
        set;
    }
}

它包含在列表中:

List<RequestEntry> RequestEntries = new List<RequestEntry>()
{
    new RequestEntry{RequestId = 1, RequestedDate = new DateTime(2018,06,01), ApproverUserId = "STEVES", ApproverUserName = "Steve Smith"}, 
    new RequestEntry{RequestId = 1, RequestedDate = new DateTime(2018,06,01), ApproverUserId = "GRAHAMS", ApproverUserName = "Graham Smith" }, 
    new RequestEntry{RequestId = 2, RequestedDate = new DateTime(2018,06,02), ApproverUserId = "STEVES", ApproverUserName = "Steve Smith"}, 
    new RequestEntry{RequestId = 3, RequestedDate = new DateTime(2018,06,03), ApproverUserId = "ROBINS", ApproverUserName = "Robin Smith"}, 
    new RequestEntry{RequestId = 3, RequestedDate = new DateTime(2018,06,03), ApproverUserId = "CHRISS", ApproverUserName = "Chris Smith"}, 
    new RequestEntry{RequestId = 3, RequestedDate = new DateTime(2018,06,03), ApproverUserId = "LIAMS", ApproverUserName = "Liam Smith"} 
};

目标

我的预期结果是这样的:

public class RequestWithApprover
{
    public int RequestId
    {
        get;
        set;
    }

    public DateTime RequestedDate
    {
        get;
        set;
    }

    public List<string> ApproverUserIds
    {
        get;
        set;
    }

    public List<RequestApprover> RequestApprovers
    {
        get;
        set;
    }
}

在哪里RequestApprover定义为

public class RequestApprover
{
    public string ApproverUserId
    {
        get;
        set;
    }

    public string ApproverUserName
    {
        get;
        set;
    }
}

工作原理

在遵循 Stackoverflow 中的一些早期场景之后，我能够写到获得 List 中定义的程度

var results = (
            from r in RequestEntries
            group r by new
            {
                r.RequestId, r.RequestedDate
            }
            into g
            select new RequestWithApprover()
            {
                RequestId = g.Key.RequestId, 
                RequestedDate = g.Key.RequestedDate, 
                ApproverUserIds = g.Select(c => c.ApproverUserId).ToList() 
                //----> Here I am able to get a List<string> but need to be in List<RequestWithApprover>
            }).ToList();

我怎样才能得到 List<RequestWithApprover> 的结果？ ？

我的 DotNetFiddle

Answer 1

为了实现这个目标，您可以在其中创建所需对象的 Select 方法。我认为这对您有用:

var results = (
        from r in RequestEntries
        group r by new
        {
            r.RequestId, r.RequestedDate
        }
        into g
        select new RequestWithApprover()
        {
            RequestId = g.Key.RequestId, 
            RequestedDate = g.Key.RequestedDate, 
            ApproverUserIds = g.Select(c => c.ApproverUserId).ToList() 
            RequestApprovers = g.Select(c => new RequestApprover(){ApproverUserName = c.ApproverUserName, ApproverUserId = c.ApproverUserId}).ToList()
        }).ToList();