不过，我正在尝试返回结果列表。每当没有结果时，我都会收到上面发布的错误消息。然而，这很奇怪，因为每当我添加变量 q 而不是 return 时，它只是不返回任何结果并且对此没有问题。我更愿意按照我现在正在做的方式去做，有人知道查询有什么问题吗？每当我在 LINQPad 中运行它时，它都可以正常工作。
public IQueryable<ClaimNumberReport> GetClaimsByClaimNumber(int ClientID, int ClaimID) {
/*var q = */ return (from d in camOnlineDb.Details
join a in camOnlineDb.Areas
on new { a = d.ClientID, b = d.AreaID ?? 0 }
equals new { a = a.ClientID, b = a.AreaID }
where d.ClientID == ClientID
join r in camOnlineDb.Reasons
on new { a = d.ClientID, b = d.ReasonID ?? 0 }
equals new { a = r.ClientID, b = r.ReasonID }
join sd in camOnlineDb.SuppDepts
on new { a = d.ClientID, b = d.CategoryID ?? 0 }
equals new { a = sd.ClientID, b = sd.CategoryID } into sdd
from sd in sdd.DefaultIfEmpty()
join h in camOnlineDb.Headers
on new { d.ClientID, d.ClaimID}
equals new { h.ClientID, h.ClaimID }
where h.ClaimID == ClaimID
join su in camOnlineDb.Suppliers
on new { h.ClientID, h.SupplierID }
equals new {su.ClientID, su.SupplierID }
join cp in camOnlineDb.ClaimPacks
on new { h.ClientID, h.ClaimID }
equals new { cp.ClientID, cp.ClaimID }
join rev in camOnlineDb.Reviews
on new { h.ClientID, h.ReviewID }
equals new { rev.ClientID, rev.ReviewID }
join revp in camOnlineDb.ReviewPeriods
on new { a = rev.ClientID, b = rev.ReviewPeriodID ?? 0 }
equals new { a = revp.ClientID, b = revp.ReviewPeriodID }
join st in camOnlineDb.Statuses
on new { a = d.ClientID, b = d.StatusID ?? 0 }
equals new { a = st.ClientID, b = st.StatusID }
join stcm in camOnlineDb.StatusCategoryMappings
on new { st.ClientID, st.StatusID }
equals new { stcm.ClientID, stcm.StatusID }
join stc in camOnlineDb.StatusCategories
on new { stcm.StatusCategoryID }
equals new { stc.StatusCategoryID }
where stc.StatusCategoryTypeID == 1
select new ClaimNumberReport {
TypeID = d.ClaimTypeID,
CPAttached = cp.FileName,
ReviewPeriodName = revp.ReviewPeriodName,
ClaimID = d.ClaimID,
Line = d.ClaimLine,
AccountNo = su.AccountNo,
SupplierName = su.SupplierName,
Amount = d.Amount,
Status = st.StatusDesc,
DateSent = d.DateSent,
DayOS = d.DaysOS,
NominalPeriod = d.NominalPeriod,
SLInvoiceNo = d.SLInvoiceNo,
Area = a.AreaDesc,
DebitRef = d.DebitFile,
DebitDate = d.JournalDate,
DeductDate = d.DeductDate,
StatusCategoryID = stc.StatusCategoryID,
StatusCategoryDesc = stc.StatusCategoryDesc,
APLReason = r.ReasonDesc,
ClientID = d.ClientID,
DeptNo = sd.DepartmentID,
DeptName = sd.DepartmentName,
Agreed = d.Agreed
});
/*return q;*/
}
最佳答案
此错误是由于查询结果类型具有非可空类型的列/属性但生成的查询结果为 NULL 值的情况引起的。
这可以被认为是错误或不是。很难看出 L2S 团队应该在这里做些什么不同的事情。我认为他们应该添加更好的错误消息。这个错误是阴险的，因为它有时只会在异常数据下出现在生产中......
您的左连接 (sd) 似乎不匹配，您选择的 sd.* 属性之一必须是 int。像这样解决:
DeptNo = (int?)sd.DepartmentID, //Cast to nullable
d.CategoryID ?? 0
你在这干什么？这似乎是一种使连接编译的方法。最好使用:
join r in camOnlineDb.Reasons
on new { a = d.ClientID, b = (int?)d.ReasonID }
equals new { a = r.ClientID, b = (int?)r.ReasonID }
此转换使匿名类型签名兼容。生成的 SQL 现在应该更快了。如果你说 x ?? 0 转换为 COALESCE(x, 0) 可以防止使用索引等。
关于c# - 转换为值类型 'System.Int32' 失败，因为具体化值为空。，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31135522/