将Linq分组结果转换为对象

Question

概述

当我有一个类作为：

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

    public string ApproverUserId
    {
        get;
        set;
    }

    public string ApproverUserName
    {
        get;
        set;
    }

    public DateTime RequestedDate
    {
        get;
        set;
    }
}

并且它包含在一个列表中，如下：

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

我的期望结果是：

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;
    }
}

其中RequestApprover的定义如下

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

    public string ApproverUserName
    {
        get;
        set;
    }
}

工作原理

在跟随Stackoverflow中的一些早期情景之后，我能够撰写代码以获取一个已定义为List的结果。

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();

我该如何获得 List<RequestWithApprover> 的结果？

我的DotNetFiddle

- hiFI

---

类似于 RequestApprovers = g.Select(c => new RequestApprover { ApproverUserId = c.ApproverUserId，ApproverUserName = c.ApproverUserName }）.ToList（）的内容。 - Janus Pienaar

Answer 1

为了实现这个目标，您可以使用Select方法并在其中创建所需的对象。 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();

- Alex Riabov

---

太好了！请注意需要进行一小处更正：RequestWithApprover.RequestApprovers 接受的是 List<RequestApprover> 而不是 List<RequestWithApprover> :) - hiFI