C# 林奇集团；总和

我真的以为我和linq相处得很好，直到现在，我有一对多的关系，我需要返回Jobitems（Jobitems.Cost）的总和

List jobItems=BLL.Inventory.JobItem.GetAllActive（强制重新加载）；
列表作业=BLL.Inventory.Job.GetAllActive（强制重新加载）；
var getInvoicedItems2=来自作业中的j
将ji加入j.JobId上的jobItems等于ji.JobId
选择新建{JobCost=ji.Cost，JobId=ji.JobId}；

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到目前为止，我已经做到了，但我不知道如何按ji对所有作业进行分组。JobId

您可以使用组联接将所有作业项分组到一个集合中，然后计算该集合中所有成本的总和

var jobItems = BLL.Inventory.JobItem.GetAllActive(forceReload);
var jobs = BLL.Inventory.Job.GetAllActive(forceReload);
var query = from j in jobs
            join ji in JobItems on j.JobId equals ji.JobId into items
            select new
            {
                JobId = j.JobId,
                JobCost = items.Sum(ji => ji.Cost),
            };

似乎有效

var jobItems = BLL.Inventory.JobItem.GetAllActive(forceReload);
var jobs = BLL.Inventory.Job.GetAllActive(forceReload);
var query = from j in jobs
            join ji in JobItems on j.JobId equals ji.JobId into items
            select new
            {
                JobId = j.JobId,
                JobCost = items.Sum(ji => ji.Cost),
            };

var getInvoicedItems2 = from ji in jobItems
    group ji by ji.JobId
    into g
    select new {JobId = g.Key, Cost = g.Sum(p => p.Cost)};

var getInvoicedItems = from j in jobs
    from s in schedules
    from i in invoices
    from jj in getInvoicedItems2
    where i.JobId == j.JobId && j.ScheduleId == s.ScheduleId && jj.JobId == j.JobId
    select new { JobCost = jj.Cost, InvoiceDate = i.CreatedDate, Status = i.Status, };