LINQ to Entities无法识别方法’Int32

public ActionResult ReadXMLDevices(int groupID) { var query = from k in XMLEntities.unassigneditems where k.DevOrAcc == true && k.Group == groupID select k; var view_query = from i in query select new GetFreeDevices { MArticleNumber = i.ArticleNumber, MFirmware = i.Firmware, MGroup = i.Group, MName = i.Name, MSoftware = i.SoftwareVersion, SA = GetNumberOfDevices(i.ArticleNumber,2), STH = GetNumberOfDevices(i.ArticleNumber,3), SASTH = GetNumberOfDevices(i.ArticleNumber,7) }; return PartialView(view_query); } public int GetNumberOfDevices(string artNo,int loc) { var num_dev = (from k in XMLEntities.deviceview where k.Reserved == false && k.Sold == false && k.LocationNameId == loc && k.ArticleNumber == artNo select k).Count(); return num_dev; } 

错误：

LINQ to Entities无法识别方法’Int32 GetNumberOfDevices（System.String，Int32）’方法，并且此方法无法转换为存储表达式。 怎么解决这个???

Answer 1

您可以将查询拆分为两个，以确保在调用GetNumberOfDevices()方法之前列表在内存中。 您可以通过将结果转换为List或在本例中为List来在内存中进行查询。 这样，LinQ to Entities不必对XML进行任何翻译，您可以使用GetNumberOfDevices()方法。

 var view_query = (from i in query select new GetFreeDevices { MArticleNumber = i.ArticleNumber, MFirmware = i.Firmware, MGroup = i.Group, MName = i.Name, MSoftware = i.SoftwareVersion }).ToList(); var result_query = from i in query select new GetFreeDevices { MArticleNumber = i.MArticleNumber, MFirmware = i.MFirmware, MGroup = i.MGroup, MName = i.MName, MSoftware = i.MSoftware, SA = GetNumberOfDevices(i.MArticleNumber,2), STH = GetNumberOfDevices(i.MArticleNumber,3), SASTH = GetNumberOfDevices(i.MArticleNumber,7) }; return PartialView(result_query); 

请注意，最后一个语句要求PartialView接受列表或IEnumerable而不是IQueryable 。

Answer 2

还有另一种简单的方法。

首先，将数据从数据库加载到内存：

 // ... var query_view = from i in query select i; query_view.Load(); // ... 

然后，使用linq-to-objects做任何你想做的事情，而不是L2E：

 var view_query_1 = from i in DbContext.myEntities.Local select new GetFreeDevices { MArticleNumber = i.ArticleNumber, MFirmware = i.Firmware, MGroup = i.Group, MName = i.Name, MSoftware = i.SoftwareVersion, SA = GetNumberOfDevices(i.ArticleNumber,2), // STH = GetNumberOfDevices(i.ArticleNumber,3), // These are now ok! SASTH = GetNumberOfDevices(i.ArticleNumber,7) // }; return PartialView(view_query_1.AsEnumerable()); 

您可以将此技巧用于L2E不支持的任何方法。