實體框架Linq SelectMany有條件

Question

我一直試圖為我想寫的linq查詢找到合適的解決方案。

在我的模型結構中，我有我的Item類，它包含一個PaymentRecords列表。 我希望我的查詢實現的是：

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
}   

選擇所有項目，其中PaymentRecord列表與下面的條件匹配（工作正常），或者PaymentRecord為null，例如Items類沒有PaymentRecord。 有沒有辦法做到這一點？

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();

理想情況下，我想做類似下面的事情，但我無法得到類似的工作：

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();

根據給出的答案，我得到了這個：

 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

你可以在沒有SelectMany情況下做到這一點

        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();

這樣你就得到了List<Item>而不是List<PaymentRecord>

Answer 2

選擇所有項目，其中PaymentRecord列表與下面的條件匹配（工作正常），或者PaymentRecord為null，例如Items類沒有PaymentRecord。

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

我沒有看到在這里使用SelectMany任何理由。 簡單Where條件可以完成工作。