在我们的在线结算应用程序中,我们提供了客户收到的账单及其付款的账单摘要.
为了实现这一点,我必须先付款然后将它们与账单相匹配.所以我做了类似的事情：
foreach (BillPaymentSummary payment in billPayments)
{
DateTime dt = payment.DueDate;
// Debug errors on this next line
var summary = (from a in db.BillHistories
where a.CustomerId == customerNumber && a.DueDate == dt && a.Type == "BILL"
select new BillSummary
{
Id = a.Id,CustomerId = a.CustomerId,DueDate = a.DueDate,PrevIoUsBalance = a.PrevIoUsBalance.Value,TotalBill = a.TotalBill.Value,Type = a.Type,IsFinalBill = a.IsFinalBill
}).SingleOrDefault();
if (summary != null)
{
summary.PayDate = payment.PaidDate;
summary.AmountPaid = payment.AmountPaid;
returnSummaries.Add(summary);
}
else
{
summary = (from a in db.BillHistories
where a.CustomerId == customerNumber && a.DueDate == payment.DueDate && a.Type == "ADJ "
select new BillSummary
{
Id = a.Id,IsFinalBill = a.IsFinalBill
}).SingleOrDefault();
if (summary != null)
{
summary.PayDate = payment.PaidDate;
summary.AmountPaid = payment.AmountPaid;
returnSummaries.Add(summary);
}
}
}
我一直在玩这个,但不管我做什么,我收到以下错误信息：
The entity or complex type ‘UtilityBill.Domain.Concrete.BillSummary’ cannot be constructed in a LINQ to Entities query.
是因为我在查询中运行查询？我怎样才能解决这个错误？
我曾尝试在谷歌搜索答案并看到很多答案,但似乎没有一个解释我的问题.
解决方法
您无法投影到映射的实体.在进行映射之前,您必须调用ToList().
或者更好的是,更改为以下内容(调用FirstOrDefault将执行查询并允许您填充对象)：
var summary = db.BillHistories.FirstOrDefault(a => a.CustomerId == customerNumber && a.DueDate == dt && a.Type == "BILL").Select(x => new BillSummary
{
Id = a.Id,IsFinalBill = a.IsFinalBill
});
要将自己与实体框架分离,您可能还需要考虑使用不同的模型类而不是实体框架模型.