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c# - 实体框架中的不等于列表<>

问题描述

我有4个表如下：

表 1 位置 A

 public class CustmLocationA  
 {
     public int Location1_ID { get; set; }
     public string Location1 { get; set; }
     public string Location1_Descrip { get; set; }
     public bool IsActive { get; set; }
 }

表 2 位置 B

 public class CustmLocationB
 {
     public int Location2_ID { get; set; }
     public string Location2 { get; set; }
     public string Location2_Descrip { get; set; }
     public int Location1_ID { get; set; }
     public bool IsActive { get; set; }
 }

表 3 位置 C

 public class CustmLocationC 
 {
     public int Location3_ID { get; set; }
     public string Location3 { get; set; }
     public string Location3_Descrip { get; set; }
     public int Location2_ID { get; set; }
     public bool IsActive { get; set; }

     //Location B data
     public string Location2 { get; set; }

     [NotMapped] 
     public bool LocBIsActive { get; set; }

     //location A data
     [NotMapped] 
     public int Location1_ID { get; set; }

     [NotMapped] 
     public string Location1 { get; set; }

     [NotMapped] 
     public bool LocAIsActive { get; set; }

     [NotMapped] 
     public string LocAandB { get; set; }
 }

表 4：

 public class CustmContact
 {
     public int contactID { get; set; }
     public int Location3_ID { get; set; }
     public int UserID { get; set; }
     public bool Notify { get; set; }
     public bool Access { get; set; }

     [NotMapped]
     public string UserName { get; set; }

     [NotMapped]
     public string LocationAll { get; set; }
 }

我试过的：

我试图在位置 A 和 B 表中选择所有位置 C 以及相关表信息，之后我需要在表联系人（第 4 个表）中选择选定的用户位置，之后我需要从选定位置中删除所有选定的用户位置，但我发现不能应用于这一行中 int 类型的操作数和 list of

(a.Location3_ID != (from z in db.contacts where z.UserID == UserID select z.Location3_ID))



 //Get Un-selected location by user ID

 public List GetSelectedLocByUID (int UserID = 0)
 {


 var data = (from LocC in db.locationsC

 join LocB in db.locationsB on LocC.Location2_ID equals LocB.Location2_ID

 join LocA in db.locationsA on LocB.Location1_ID equals LocA.Location1_ID

 select new CustmLocationC
 {

 Location1_ID = LocA.Location1_ID,

 Location1 = LocA.Location1,

 LocAIsActive = LocA.IsActive,

 Location2_ID = LocB.Location2_ID,

 Location2 = LocB.Location2,

 LocBIsActive = LocB.IsActive,

 Location3_ID = LocC.Location3_ID,

 Location3 = LocC.Location3,

 Location3_Descrip = LocC.Location3_Descrip,

 LocAandB = LocA.Location1 + "-" + LocB.Location2,

 IsActive = LocC.IsActive

 }).Where(a => a.LocAIsActive == true && a.LocBIsActive == true && a.IsActive == true 


 && **a.Location3_ID != (from z in db.contacts where z.UserID == UserID select z.Location3_ID)**


 ).OrderBy(a => a.Location1).ToList();


 return (data);
 }

标签： c#linq

解决方案

（Bryian Tan 的回答）

当前的逻辑“a.Location3_ID != (from z in db.contacts where z.UserID == UserID select z.Location3_ID)”试图将一个位置与一个或多个位置进行比较。这不起作用，比如说 1 个苹果是否等于 1 个或更多苹果。

根据我在这里发布的内容

//store the list of Location3_ID for a user in a list
List<int> loc3s = (from z in db.contacts
                               where z.UserID == UserID 
                               select z.Location3_ID).ToList();
//then replace a.Location3_ID != (from z in db.contacts where z.UserID == UserID select z.Location3_ID) with below
//return all the result where Location3_ID not belong to the user
!loc3s.Contains(a.Location3_ID )

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