C# EF核心错误："；不支持对实体类型进行比较，因为它是无键实体；在进行外部连接时

我有两张桌子。一个用于发票，一个用于付款。 invoice表的架构如下所示

public class Invoice
{
  public Guid ID {get;set;}
  public string InvoiceNum {get;set;}
  public decimal Amount {get;set;}  
}

public class Payment
{
  public Guid ID {get;set;}
  public InvoiceID {get;set;}
  public decimal PaidAmount {get;set;}
  public DateTimeOffset? VoidDate {get;set;}
  public virtual Invoice Invoice { get; set; }
}

付款表的模式如下所示

public class Invoice
{
  public Guid ID {get;set;}
  public string InvoiceNum {get;set;}
  public decimal Amount {get;set;}  
}

public class Payment
{
  public Guid ID {get;set;}
  public InvoiceID {get;set;}
  public decimal PaidAmount {get;set;}
  public DateTimeOffset? VoidDate {get;set;}
  public virtual Invoice Invoice { get; set; }
}

我想得到所有未全额付款的发票。首先，我声明了一个名为PaymentStatus的实体

public class PaymentStatus
{
  public Guid InvoiceID {get;set;}
  public decimal TotalPaidAmount {get;set;}
}

然后在我的DbContext类中

public virtual DbSet<Invoice> Invoices { get; set; }

public virtual DbSet<PaymentStatus> PaymentStatuses { get; set; }

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
            modelBuilder.Entity<PaymentStatus>().ToQuery(() =>
                Payment.Where(r => r.VoidDate == null)
                    .GroupBy(r => r.InvoiceID)
                    .Select(r => new PaymentStatus{ InvoiceID = r.Key, TotalPaidAmount = r.Sum(p => p.PaidAmount) }))
                .HasNoKey()
                .HasOne(r=>r.Invoice)
                .WithOne().HasForeignKey<PaymentStatus>(r=>r.InvoiceID);
}

如果更改为

PaidAmount = pay.TotalPaidAmount 

然后它在UnitTest（使用InMemory数据库）中工作，但在SQL Server中失败，因为转换后的SQL使用

WHERE (inv.Amount > pay.PaidAmount)

如果发票未付款，则PaymentStatus没有发票的相应记录，因此pay.PaidAmount为空（非零）。不满足库存金额>空

我正在使用EntityFrameworkCore 3.1.5

我不明白的是为什么

pay==null ? 0 : pay.TotalPaidAmount

---

抛出错误以及如何解决它

我通过使TotalPaidAmount在PaymentStatus中为空来解决这个问题

public class PaymentStatus
{
  public Guid InvoiceID {get;set;}
  public decimal? TotalPaidAmount {get;set;}
}

然后更改“获取应收款”中的查询

public Task<List<Receivables>> GetReceivables()
{
  var qry = from inv in MyDbContext.Invoices
    from pay in MyDbContext.PaymentStatuses.Where(p => p.InvoiceID == inv.ID).DefaultIfEmpty()
    select new Receivables
    {
      InvoiceID = inv.ID,
      InvoiceAmount = inv.Amount,
      PaidAmount = pay.TotalPaidAmount ?? 0,
    };
  return qry.Where(r=>r.InvoiceAmount > r.PaidAmount ).ToListAsync();
}

public任务getresponses（）
{
var qry=来自MyDbContext.Invoices中的inv
从MyDbContext.PaymentStatuses.Where（p=>p.InvoiceID==inv.ID）中的pay.DefaultIfEmpty（）
选择新的应收账款
{
发票ID=发票ID，
发票金额=发票金额，
PaidAmount=pay.TotalPaidAmount±0，
};
返回qry.Where（r=>r.InvoiceAmount>r.PaidAmount.toListSync（）；
}