LINQ to Entities不识别方法***，因此该方法无法转换为存储表达式_.NET_编程开发_程序员俱乐部

我的程序里有这么一段代码：

order.OrderExpressInfo = (from oei in orderExpressRepository.Entities
                                      where oei.OrderId == order.OrderId
                                      select new EbcBuy.Bll.Orders.Models.OrderExpress
                                      {
                                          ContentInfo = oei.ContentInfo,
                                          CreatedTime = oei.CreatedTime,
                                          CreatedUserId = oei.CreatedUserId,
                                          ExpressId = oei.ExpressId,
                                          ExpressName = oei.ExpressName,
                                          ExpressOrderId = oei.ExpressOrderId,
                                          Freight = oei.Freight,
                                          Manifest = oei.Manifest,
                                          OrderId = oei.OrderId,
                                          ReceiverContactInfo = new ContactInfoModel()
                                            {
                                                ZipCode = oei.CustomerZipCode,
                                                Telephone = oei.CustomerPhone,
                                                MobilePhone = oei.CustomerTel,
                                                Address = oei.CustomerAddress,
                                                LinkMan = oei.CustomerReceiverName,
                                                ProvinceId = oei.CustomerArea.ProvinceId,
                                                ProvinceName = oei.CustomerArea.ProvinceName,
                                                CityId = oei.CustomerArea.CityId,
                                                CityName = oei.CustomerArea.CityName,
                                                CountyId = oei.CustomerArea.DistrictId,
                                                CountyName = oei.CustomerArea.DistrictName
                                            },
                                          ShopId = order.OrderId,
                                          ShopName = order.ShopName,
                                          ShopContactInfo = new ContactInfoModel()
                                              {
                                                  ZipCode = oei.ShopZipCode,
                                                  Telephone = oei.ShopTel,
                                                  MobilePhone = oei.ShopPhone,
                                                  Address = oei.ShopAddress,
                                                  LinkMan = oei.ShopLinkMan,
                                                  ProvinceId = oei.ShopArea.ProvinceId,
                                                  ProvinceName = oei.ShopArea.ProvinceName,
                                                  CityId = oei.ShopArea.CityId,
                                                  CityName = oei.ShopArea.CityName,
                                                  CountyId = oei.ShopArea.DistrictId,
                                                  CountyName = oei.ShopArea.DistrictName
                                              }
                                      }).FirstOrDefault();

其中，ContactInfoModel是一个实体类，定义了买家或卖家的contact信息，  实体类 EbcBuy.Bll.Orders.Models.OrderExpress
具备两个该类型的属性， ReceiverContactInfo和ShopContactInfo。 这里使用linq to entity要给这2个属性赋值， 要注意了，这里给ContactInfoModel初始化设置的属性个数和顺序必须相同。 否则，运行时会报如下异常：

“System.NotSupportedException”类型的未经处理的异常在 EntityFramework.dll 中发生

其他信息: 在单个 LINQ to Entities 查询中的两个结构上不兼容的初始化过程中出现类型“EbcBuy.Bll.Common.Models.ContactInfoModel”。类型可以在同一查询中的两个位置初始化，但前提是在这两个位置设置了相同的属性，且这些属性是以相同的顺序设置的。

我这个ContactInfoModel在项目里好多的linq to entity代码里进行这样的初始化， 为了提高复用，我把上面的初始化封装成了一个方法， 供各处调用。 修改后的代码如下：

 order.OrderExpressInfo = (from oei in orderExpressRepository.Entities
                                      where oei.OrderId == order.OrderId
                                      select new EbcBuy.Bll.Orders.Models.OrderExpress
                                      {
                                          ContentInfo = oei.ContentInfo,
                                          CreatedTime = oei.CreatedTime,
                                          CreatedUserId = oei.CreatedUserId,
                                          ExpressId = oei.ExpressId,
                                          ExpressName = oei.ExpressName,
                                          ExpressOrderId = oei.ExpressOrderId,
                                          Freight = oei.Freight,
                                          Manifest = oei.Manifest,
                                          OrderId = oei.OrderId,
                                          ReceiverContactInfo = GetCustomerContactInfoModelFromPO(oei),
                                          ShopId = order.OrderId,
                                          ShopName = order.ShopName,
                                          ShopContactInfo = GetShopContactInfoModelFromPO(oei)
                                      }).FirstOrDefault();

GetCustomerContactInfoModelFromPO和GetShopContactInfoModelFromPO定义很简单，你懂的。
结果，在运行时，文章标题提到的异常出现了：
“System.NotSupportedException”类型的未经处理的异常在 EntityFramework.dll 中发生 

其他信息: LINQ to Entities 不识别方法“EbcBuy.Bll.Common.Models.ContactInfoModel GetCustomerContactInfoModelFromPO(EbcBuy.Dal.Orders.Models.OrderInfo)”，因此该方法无法转换为存储表达式。

【园子里搜索了一下， 有如下结论】在LINQ to Entities 中,使用lambada或linq时,变量一定要提前转换好,可不能到lambada里或linq里再转换。如:

var o= _db.Dictionary.Where(x => x.Type.Equals(type4.ToString()));

.ToString必然产生错误,应该:

string t=type4.ToString();

var o= _db.Dictionary.Where(x => x.Type.Equals(t));

用lambada或linq时,不要尝试去转换内置类型,是不允许的,如:

string t=type4.ToString();

var o= _db.Dictionary.Where(x => Convert.ToString(x.Type).Equals(t));

Convert.ToString必然要出错.

可以考虑使用如下方式：

using System.Data.Objects.SqlClient;  //在 System.Data.Entity.dll 中
//获取市级地区
public JsonResult GetCity(string id)
{ 
    var city = from c in db.AreaDivide
    where SqlFunctions.StringConvert((double)c.ParentID) == id
    select new { text = c.AreaName, value = c.ID };

    return Json(city.ToList(), JsonRequestBehavior.AllowGet);
}

不过，像我这种情况，无法复用的话，还真是谈不上简洁性了。不晓得还有没有什么好的解决办法...