EF 4.1 POCO查詢

Question

我有這個POCO，我想返回特定公司的用戶列表。

public class Company 
{ 
    public AccreditedCompany() 
    { 
     this.Branches = new HashSet<Branch>(); 
    } 

    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity), ScaffoldColumn(false)] 
    public int CompanyId { get; set; } 
    public bool Active { get; set; } 

    public virtual ICollection<Branch> Branches { get; set; }   
} 

public class Branch 
{ 
    public Branch() 
    { 
     this.Users = new HashSet<User>(); 
    } 

    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity), ScaffoldColumn(false)] 
    public int BranchId { get; set; } 
    public int CompanyId { get; set; } 
    public string Name { get; set; } 
    public string ContactName { get; set; } 

    public virtual Company Company { get; set;} 
    public virtual ICollection<User> Users { get; set; } 
} 

public class User 
{ 

    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity), ScaffoldColumn(false)] 
    public int UserId { get; set; } 
    public int BranchId { get; set; } 
    public string ComputerSN { get; set; } 
    public string CameraSN { get; set; } 

    public virtual Branch Branch { get; set; }   
} 

這是我的LINQ查詢：

var company = (from u in objDataContext.Companies.Include(c=>c.Branches.Select(v=>v.Users)) 
    where u.CompanyId == 8 select u).FirstOrDefault(); 

IQueryable<User> users = (from j in company.Branches select j.Users); 

我對第二個查詢此編譯錯誤：

錯誤2無法隱式轉換類型 「System.Collections.Generic。 IEnumerable>' 改爲'System.Linq.IQueryable'。一個顯式轉換存在（被 缺少強制轉換？）

我想獲得用戶的列表，類似於普通的SQL語句等預先

SELECT dbo.Users.* FROM Branches 
INNER JOIN dbo.Users ON dbo.Branches.BranchId = dbo.Users.BranchId 
INNER JOIN dbo.Companies ON dbo.Branches.CompanyId = dbo.Companies.CompanyId 
WHERE  (dbo.Companies.CompanyId = 8) 

感謝。

Answer 1

您的用戶查詢可以是：

IEnumerable<User> users = company.Branches.SelectMany(branch => branch.Users); 

這將返回所有用戶在該公司的任何分支。

Answer 2

它看起來對我來說，你可以只使用：

IQueryable<User> users = objDataContext.Users 
         .Where(u => u.Branch.CompanyId == 8); 

我注意到你有你的Branch實體都Company和CompanyId，雖然。這似乎是多餘的，儘管它稍微簡化了這個查詢。你應該能夠擺脫Branch.CompanyId和User.BranchId並只使用實體關聯。