抓住这个Linq查询。这是实体框架。查询会转换为不同的模型对象。如果我评论或删除我指示为导致错误的代码区域，则linq查询有效。但在我看来，我应该能够编写这样的查询而不会出现此错误：
无法创建“DomainModel.Model.CustomerAddress”类型的空常量值。在此上下文中仅支持实体类型，枚举类型或基元类型。
任何人都可以告诉我为什么我不能或更重要的是我需要改变它才能使其发挥作用？
由于
var orders = from o in _db.Orders
.Include("User")
.Include("OrderItems.Inventories.Product")
.Include("Transactions")
.Include("CustomerAddressBilling.Address")
.Include("CustomerAddressBilling.Customer")
.Include("CustomerAddressBilling.Contact")
.Include("CustomerAddressShipping.Address")
.Include("CustomerAddressShipping.Customer")
.Include("CustomerAddressShipping.Contact")
.Include("ShippingMethod")
// this works ok
let items = (o.OrderItems.Select(i => new Model.OrderItem
{
OrderItemId = i.OrderItemId,
OrderId = i.OrderId,
DateAdded = i.CreateDate,
LineItemPrice = i.Inventories.Sum(ii => ii.Product.Price),
Product = i.Inventories.FirstOrDefault().Product,
Quantity = i.Inventories.Count()
}))
// this works ok
let transactions = (o.Transactions.Select(t => new Model.Transaction
{
Id = t.TransactionId,
OrderId = t.OrderId,
Amount = t.Amount,
AuthorizationCode = t.AuthorizationCode,
DateExecuted = t.TransactionDate,
Notes = t.Notes,
Processor = (Model.TransactionProcessor)t.ProcessorId
}))
// this causes the error
let cab = o.CustAddBillingId.HasValue ? (new Model.CustomerAddress
{
Id = o.CustomerAddressBilling.CustAddId,
UserName = o.User.UserName,
FirstName = o.CustomerAddressBilling.Customer.FirstName,
LastName = o.CustomerAddressBilling.Customer.LastName,
MiddleInitial = o.CustomerAddressBilling.Customer.MiddleName,
Salutation = o.CustomerAddressBilling.Customer.Salutation,
Suffix = o.CustomerAddressBilling.Customer.Suffix,
Street1 = o.CustomerAddressBilling.Address.Line1,
Street2 = o.CustomerAddressBilling.Address.Line2,
Street3 = o.CustomerAddressBilling.Address.Line3,
City = o.CustomerAddressBilling.Address.City,
StateOrProvince = o.CustomerAddressBilling.Address.State,
Zip = o.CustomerAddressBilling.Address.PostalCode,
Country = o.CustomerAddressBilling.Address.Country,
Latitude = o.CustomerAddressBilling.Address.Lat,
Longitude = o.CustomerAddressBilling.Address.Long,
Email = o.CustomerAddressBilling.Contact.ContactInfo,
IsDefault = o.CustomerAddressBilling.IsPrimary
}) : default(Model.CustomerAddress)
// this causes the error
let cas = o.CustAddShippingId.HasValue ? (new Model.CustomerAddress
{
Id = o.CustomerAddressShipping.CustAddId,
UserName = o.User.UserName,
FirstName = o.CustomerAddressShipping.Customer.FirstName,
LastName = o.CustomerAddressShipping.Customer.LastName,
MiddleInitial = o.CustomerAddressShipping.Customer.MiddleName,
Salutation = o.CustomerAddressShipping.Customer.Salutation,
Suffix = o.CustomerAddressShipping.Customer.Suffix,
Street1 = o.CustomerAddressShipping.Address.Line1,
Street2 = o.CustomerAddressShipping.Address.Line2,
Street3 = o.CustomerAddressShipping.Address.Line3,
City = o.CustomerAddressShipping.Address.City,
StateOrProvince = o.CustomerAddressShipping.Address.State,
Zip = o.CustomerAddressShipping.Address.PostalCode,
Country = o.CustomerAddressShipping.Address.Country,
Latitude = o.CustomerAddressShipping.Address.Lat,
Longitude = o.CustomerAddressShipping.Address.Long,
Email = o.CustomerAddressShipping.Contact.ContactInfo,
IsDefault = o.CustomerAddressShipping.IsPrimary
}) : default(Model.CustomerAddress)
// this causes the error
let sm = o.ShippingMethodId.HasValue ? (new ShippingMethod
{
Id = o.ShippingMethod.ShippingMethodId,
Carrier = o.ShippingMethod.Carrier,
ServiceName = o.ShippingMethod.ServiceName,
BaseRate = o.ShippingMethod.BaseRate,
RatePerPound = o.ShippingMethod.RatePerPound,
DaysToDeliver = o.ShippingMethod.DaysToDeliver,
EstimatedDelivery = o.ShippingMethod.EstimatedDelivery
}) : default(ShippingMethod)
select new Model.Order
{
Id = o.OrderId,
UserName = o.User.UserName,
DateCreated = o.CreateDate,
Items = items.AsQueryable(),
Transactions = transactions.AsQueryable(),
ShippingAddressId = o.CustAddShippingId,
BillingAddressId = o.CustAddBillingId,
// have to comment these next 3 lines as well
ShippingAddress = cas,
BillingAddress = cab,
ShippingMethod = sm,
// to here
UserLanguageCode = "en",
DateShipped = o.ShippedDate,
EstimatedDelivery = o.EstimatedDelivery,
TrackingNumber = o.TrackingNumber,
TaxAmount = o.TaxAmount,
DiscountReason = o.DiscountReason,
DiscountAmount = o.DiscountAmount
};
答案 0 :(得分：0)
好的，我已经弄明白了。问题是数据库允许对那些相关实体使用null forien密钥，我更改了数据库，因此forien密钥不可为空，并从数据库更新了模型。我创建了代表非ShippingMethods电子和面对面的新数据，并且还有亲自的CustomerAddress，因此我可以拥有数据链接，这些数据不仅表示我没有数据，而且还表示我没有数据。
public IQueryable<Model.Order> GetOrders()
{
var orders = from o in _db.Orders
.Include("User")
.Include("OrderItems.Inventories.Product")
.Include("Transactions")
.Include("CustomerAddressBilling.Address")
.Include("CustomerAddressBilling.Customer")
.Include("CustomerAddressBilling.Contact")
.Include("CustomerAddressShipping.Address")
.Include("CustomerAddressShipping.Customer")
.Include("CustomerAddressShipping.Contact")
.Include("ShippingMethod")
let items = (o.OrderItems.Select(i => new Model.OrderItem
{
OrderItemId = i.OrderItemId,
OrderId = i.OrderId,
DateAdded = i.CreateDate,
LineItemPrice = i.Inventories.Sum(ii => ii.Product.Price),
Product = i.Inventories.FirstOrDefault().Product,
Quantity = i.Inventories.Count()
}))
let transactions = (o.Transactions.Select(t => new Model.Transaction
{
Id = t.TransactionId,
OrderId = t.OrderId,
Amount = t.Amount,
AuthorizationCode = t.AuthorizationCode,
DateExecuted = t.TransactionDate,
Notes = t.Notes,
Processor = (Model.TransactionProcessor)t.ProcessorId
}))
let cab = new Model.CustomerAddress
{
Id = o.CustomerAddressBilling.CustAddId,
UserName = o.User.UserName,
FirstName = o.CustomerAddressBilling.Customer.FirstName,
LastName = o.CustomerAddressBilling.Customer.LastName,
MiddleInitial = o.CustomerAddressBilling.Customer.MiddleName,
Salutation = o.CustomerAddressBilling.Customer.Salutation,
Suffix = o.CustomerAddressBilling.Customer.Suffix,
Street1 = o.CustomerAddressBilling.Address.Line1,
Street2 = o.CustomerAddressBilling.Address.Line2,
Street3 = o.CustomerAddressBilling.Address.Line3,
City = o.CustomerAddressBilling.Address.City,
StateOrProvince = o.CustomerAddressBilling.Address.State,
Zip = o.CustomerAddressBilling.Address.PostalCode,
Country = o.CustomerAddressBilling.Address.Country,
Latitude = o.CustomerAddressBilling.Address.Lat,
Longitude = o.CustomerAddressBilling.Address.Long,
Email = o.CustomerAddressBilling.Contact.ContactInfo,
IsDefault = o.CustomerAddressBilling.IsPrimary
}
let cas = new Model.CustomerAddress
{
Id = o.CustomerAddressShipping.CustAddId,
UserName = o.User.UserName,
FirstName = o.CustomerAddressShipping.Customer.FirstName,
LastName = o.CustomerAddressShipping.Customer.LastName,
MiddleInitial = o.CustomerAddressShipping.Customer.MiddleName,
Salutation = o.CustomerAddressShipping.Customer.Salutation,
Suffix = o.CustomerAddressShipping.Customer.Suffix,
Street1 = o.CustomerAddressShipping.Address.Line1,
Street2 = o.CustomerAddressShipping.Address.Line2,
Street3 = o.CustomerAddressShipping.Address.Line3,
City = o.CustomerAddressShipping.Address.City,
StateOrProvince = o.CustomerAddressShipping.Address.State,
Zip = o.CustomerAddressShipping.Address.PostalCode,
Country = o.CustomerAddressShipping.Address.Country,
Latitude = o.CustomerAddressShipping.Address.Lat,
Longitude = o.CustomerAddressShipping.Address.Long,
Email = o.CustomerAddressShipping.Contact.ContactInfo,
IsDefault = o.CustomerAddressShipping.IsPrimary
}
let sm = new ShippingMethod
{
Id = o.ShippingMethod.ShippingMethodId,
Carrier = o.ShippingMethod.Carrier,
ServiceName = o.ShippingMethod.ServiceName,
BaseRate = o.ShippingMethod.BaseRate,
RatePerPound = o.ShippingMethod.RatePerPound,
DaysToDeliver = o.ShippingMethod.DaysToDeliver,
EstimatedDelivery = o.ShippingMethod.EstimatedDelivery
}
select new Model.Order
{
Id = o.OrderId,
UserName = o.User.UserName,
DateCreated = o.CreateDate,
Items = items.AsQueryable(),
Transactions = transactions.AsQueryable(),
ShippingAddressId = o.CustAddShippingId,
BillingAddressId = o.CustAddBillingId,
ShippingAddress = cas,
BillingAddress = cab,
ShippingMethod = sm,
UserLanguageCode = "en",
DateShipped = o.ShippedDate,
EstimatedDelivery = o.EstimatedDelivery,
TrackingNumber = o.TrackingNumber,
TaxAmount = o.TaxAmount,
DiscountReason = o.DiscountReason,
DiscountAmount = o.DiscountAmount
};
return orders;
}
没有错误！