的更新：

Question

当我执行以下代码时：

IHotelDataAccess _hotelDataAccess= new HotelDataAccess(_entities);
int myVal = (from u in _hotelDataAccess.GetHotelsByCityId(19)
    select u).Count();

myVal按预期返回一个整数值，但是如果我尝试按以下方式返回IQueryable

return (from geoLocation in _entities.ViewGeographyLocation
 where geoLocation.CountryCode == countryCode
 orderby geoLocation.SortOrder, geoLocation.CityName
 select new ContinentModel
 {
  ContinentCode = geoLocation.ContinentCode,
  ContinentName = geoLocation.ContinentName,
  CountryCode = geoLocation.CountryCode,
  CountryName = geoLocation.CountryName,
  CityId = geoLocation.CityId,
  CityName = geoLocation.CityName,
  CityCode = geoLocation.CityName,
  TotalCount = ((from u in _hotelDataAccess.GetHotelsByCityId(19)
   select u).Count())
 });

我收到错误：

LINQ to Entities无法识别该方法 “System.Linq.IQueryable`1 [DestKosher.Model.HotelModel] GetHotelsByCityId（Int32）'方法，此方法无法翻译进入商店表达。

方法hotelDataAccess.GetHotelsByCityId（19）返回IQueryable。任何想法，帮助或解决方案将是最受欢迎的。的问候，

马丁

的更新：

此查询最初设置为查看是否通过将一个整数放入函数GetHotelsByCityId将起作用。但是，我最终想要做的是：

return (from geoLocation in _entities.ViewGeographyLocation
 where geoLocation.CountryCode == countryCode
 orderby geoLocation.SortOrder, geoLocation.CityName
 select new ContinentModel
 {
  ContinentCode = geoLocation.ContinentCode,
  ContinentName = geoLocation.ContinentName,
  CountryCode = geoLocation.CountryCode,
  CountryName = geoLocation.CountryName,
  CityId = geoLocation.CityId,
  CityName = geoLocation.CityName,
  CityCode = geoLocation.CityName,
  TotalCount = ((from u in _hotelDataAccess.GetHotelsByCityId(geoLocation.CityId)
   select u).Count())
 });

Answer 1

按照设计， LINQ to Entities 要求将整个LINQ查询表达式转换为服务器查询。在翻译查询之前，仅在客户端上评估几个不相关的子表达式（查询中不依赖于服务器结果的表达式）。不支持没有已知转换的任意方法调用，例如GetHotelsByCityId（）。

你可以这样做

var list = _hotelDataAccess.GetHotelsByCityId(19).ToList();
int myVal = (from u in list
    select u).Count();

比查询中的myval

return (from geoLocation in _entities.ViewGeographyLocation
 where geoLocation.CountryCode == countryCode
 orderby geoLocation.SortOrder, geoLocation.CityName
 select new ContinentModel
 {
  ContinentCode = geoLocation.ContinentCode,
  ContinentName = geoLocation.ContinentName,
  CountryCode = geoLocation.CountryCode,
  CountryName = geoLocation.CountryName,
  CityId = geoLocation.CityId,
  CityName = geoLocation.CityName,
  CityCode = geoLocation.CityName,
  TotalCount = myVal 
 });

继续阅读Deatil：LINQ to Entities, what is not supported?

Answer 2

尝试添加名称空间“System.Linq”，如果您有“System.Core”程序集引用，还要检查项目引用。

LINQ to Entities无法识别方法'System.Linq.IQueryable`1

的更新：

2 个答案: