实体框架Linq SelectMany有条件

Question

我已经尝试了一段时间，以寻找适合我要编写的linq查询的解决方案。

在我的模型结构中，我有Item类，其中包含PaymentRecords列表。我希望我的查询实现的是：

public class PaymentRecord
{
    public int PaymentRecordId { get; set; }

    [Required]
    public double PaymentAmount { get; set; }

    [Required]
    public DateTime DateOfPayment { get; set; }

    [Required]
    public bool FinalPayment { get; set; }

    [JsonIgnore]
    public Item Item{ get; set; }
}

public class Item
{
    public int ItemId { get; set; }

    public List<PaymentRecord> PaymentRecords {get; set;}

    ...various other properties
}   

选择所有的项目，其中PaymentRecord列表符合以下条件（可以正常工作），或者PaymentRecord为null，例如Items类没有PaymentRecord。有没有办法做到这一点？

var result = m_context.Item
            .SelectMany(
                x => x.PaymentRecords.Where(p => (p.FinalPayment == true
                                              && p.DateOfPayment >= _revenueStatementRequest.StartDate
                                              && p.DateOfPayment <= _revenueStatementRequest.EndDate)
                                              || p.FinalPayment != true),
                (x, p) => x
            )
            .ToList();

理想情况下，我想做以下类似的事情，但是我无法获得与工作类似的东西：

var result = m_context.Item
            .SelectMany(
                x => x.PaymentRecords.Where(p => (p.FinalPayment == true
                                              && p.DateOfPayment >= _revenueStatementRequest.StartDate
                                              && p.DateOfPayment <= _revenueStatementRequest.EndDate)
                                              || p.FinalPayment != true)
                || x.PaymentRecords == null,
                (x, p) => x
            )
            .ToList();

从给出的答案工作后，我有这个：

 m_context.Item.Where(c => (!
                            c.PaymentRecords.Any(q => (q.FinalPayment &&
                                                            q.DateOfPayment >= _revenueStatementRequest.StartDate &&
                                                            q.DateOfPayment <= _revenueStatementRequest.EndDate)
                                                            || q.FinalPayment != true
                                                )
                            )
                    && (c..Type == Booked || c.Type == Reserved)
                    && (c.StartDate < _revenueStatementRequest.StartDate)
                    )

Answer 1

你可以做到这一点，无需SelectMany

        List<Item> res = m_context.Items
                      .Where(c => !c.PaymentRecords
                                .Any(q => (q.FinalPayment && 
                                        q.DateOfPayment >=_revenueStatementRequest.StartDate &&
                                        q.DateOfPayment <= _revenueStatementRequest.EndDate)
                                        || !q.FinalPayment)
                            )
    //**EDIT**
    .Where(c => c.StartDate < _revenueStatementRequest.StartDate)
 //this is comment out, so we can better test on the more complex part of the query
  //.Where(c => c.Type == Booked || c.Type == Reserved)   
    .ToList();

这样你就得到了一个List<Item>而不是List<PaymentRecord>