如何将此SQL转换为Linq语句？

Question

我正在开发一种功能，可以向某些用户添加或删除角色。我将此SQL代码转换为LINQ时遇到问题。我已经测试过SQL，并且它在SQL Server Management Studio上返回了正确的结果。

由于我是LINQ的初学者，所以我发现很难转换我的SQL语句。

/* This sql code works well - returns the users which DO NOT have the role yet in the given company. */
SELECT *
FROM SP.AppUser au 
left join
( 
  SELECT distinct auc.AppUserID
   FROM SP.AppUserCompany auc
   inner join SP.AppUserCompanyRole aucr ON aucr.AppUserCompanyID = auc.AppUserCompanyID 
   where auc.CompanyID = 2 and AppRoleID = 4
) AS exist ON exist.AppUserID = au.AppUserID
Where au.AppUserID IN(2088, 38, 1926, 2059, 2058, 1925, 2097, 2061, 2072, 2064) 
and exist.AppUserID is null

// Sample code in C# to represent the entities:
AppUser stanley = new AppUser() { AppUserID = 1, FirstName = "Stanley" };
AppUser jerson = new AppUser() { AppUserID = 2, FirstName = "Jerson" };
AppUser philip = new AppUser() { AppUserID = 3, FirstName = "Philip" };
AppUser samantha = new AppUser() { AppUserID = 4, FirstName = "Samantha" };

AppUserCompany auc1 = new AppUserCompany() { AppUserCompanyID = 1, CompanyID = 1, AppUser = stanley };
AppUserCompany auc2 = new AppUserCompany() { AppUserCompanyID = 2, CompanyID = 2, AppUser = stanley };
AppUserCompany auc3 = new AppUserCompany() { AppUserCompanyID = 3, CompanyID = 1, AppUser = jerson };
AppUserCompany auc4 = new AppUserCompany() { AppUserCompanyID = 4, CompanyID = 1, AppUser = philip };
AppUserCompany auc5 = new AppUserCompany() { AppUserCompanyID = 5, CompanyID = 2, AppUser = jerson };
AppUserCompany auc6 = new AppUserCompany() { AppUserCompanyID = 6, CompanyID = 3, AppUser = stanley };

AppUserCompanyRole aucr1 = new AppUserCompanyRole() { AppUserCompanyRoleID = 1, AppUserCompany = auc1, AppRoleID = 1 };
AppUserCompanyRole aucr2 = new AppUserCompanyRole() { AppUserCompanyRoleID = 2, AppUserCompany = auc2, AppRoleID = 1 };
AppUserCompanyRole aucr3 = new AppUserCompanyRole() { AppUserCompanyRoleID = 3, AppUserCompany = auc3, AppRoleID = 1 };
AppUserCompanyRole aucr4 = new AppUserCompanyRole() { AppUserCompanyRoleID = 4, AppUserCompany = auc4, AppRoleID = 1 };
AppUserCompanyRole aucr5 = new AppUserCompanyRole() { AppUserCompanyRoleID = 5, AppUserCompany = auc5, AppRoleID = 1 };
AppUserCompanyRole aucr6 = new AppUserCompanyRole() { AppUserCompanyRoleID = 6, AppUserCompany = auc6, AppRoleID = 1 };

List<AppUser> users = new List<AppUser> { stanley, jerson, philip, samantha };
List<AppUserCompany> appUserCompanies = new List<AppUserCompany> { auc1, auc2, auc3, auc4, auc5, auc6 };
List<AppUserCompanyRole> appUserCompanyRoles = new List<AppUserCompanyRole> { aucr1, aucr2, aucr3, aucr4, aucr5, aucr6 };

// Here is the LINQ code that I tried to get the users "who already have role" in a particular company
var ids = new List<int> { 2088, 38, 1926, 2059, 2058, 1925, 2097, 2061, 2072, 2064 };
var usersToDeleteRole = (from user in appUserDataBinding.Model
  where ids.Contains(user.AppUserID)
  join auc in appUserCompanyDataBinding.Model on user.AppUserID equals auc.AppUserID into groupJoin1
     from subAuc in
     (from auc in groupJoin1
       join aucr in appUserCompanyRoleDataBinding.Model on auc.AppUserCompanyID equals aucr.AppUserCompanyID
        where auc.CompanyID == 2 && aucr.AppRoleID == 4
     select auc)
orderby user.LastName
select user).ToList();

我的预期结果将是LINQ语句，该语句返回在特定给定公司中还没有角色的用户列表。上面的SQL语句可在SSMS上使用，但无法在C＃的LINQ中使用它-这意味着我需要上面的LINQ代码的“否定”版本。

谢谢您的帮助。干杯。

Answer 1

您可以对子查询使用let语句

public class AppUser
    {
        public int AppUserID { get; set; }
        public string FirstName { get; set; }
    }

    public class AppUserCompany
    {
        public int AppUserCompanyID { get; set; }
        public int CompanyID { get; set; }
        public AppUser AppUser { get; set; }
    }

    public class AppUserCompanyRole
    {
        public int AppUserCompanyRoleID { get; set; }
        public int AppRoleID { get; set; }
        public AppUserCompany AppUserCompany { get; set; }
    }


    class Program
    {
        static void Main(string[] args)
        {

            // Sample code in C# to represent the entities:
            AppUser stanley = new AppUser() { AppUserID = 1, FirstName = "Stanley" };
            AppUser jerson = new AppUser() { AppUserID = 2, FirstName = "Jerson" };
            AppUser philip = new AppUser() { AppUserID = 3, FirstName = "Philip" };
            AppUser samantha = new AppUser() { AppUserID = 4, FirstName = "Samantha" };

            AppUserCompany auc1 = new AppUserCompany() { AppUserCompanyID = 1, CompanyID = 1, AppUser = stanley };
            AppUserCompany auc2 = new AppUserCompany() { AppUserCompanyID = 2, CompanyID = 2, AppUser = stanley };
            AppUserCompany auc3 = new AppUserCompany() { AppUserCompanyID = 3, CompanyID = 1, AppUser = jerson };
            AppUserCompany auc4 = new AppUserCompany() { AppUserCompanyID = 4, CompanyID = 1, AppUser = philip };
            AppUserCompany auc5 = new AppUserCompany() { AppUserCompanyID = 5, CompanyID = 2, AppUser = jerson };
            AppUserCompany auc6 = new AppUserCompany() { AppUserCompanyID = 6, CompanyID = 3, AppUser = stanley };

            AppUserCompanyRole aucr1 = new AppUserCompanyRole() { AppUserCompanyRoleID = 1, AppUserCompany = auc1, AppRoleID = 1 };
            AppUserCompanyRole aucr2 = new AppUserCompanyRole() { AppUserCompanyRoleID = 2, AppUserCompany = auc2, AppRoleID = 1 };
            AppUserCompanyRole aucr3 = new AppUserCompanyRole() { AppUserCompanyRoleID = 3, AppUserCompany = auc3, AppRoleID = 1 };
            AppUserCompanyRole aucr4 = new AppUserCompanyRole() { AppUserCompanyRoleID = 4, AppUserCompany = auc4, AppRoleID = 1 };
            AppUserCompanyRole aucr5 = new AppUserCompanyRole() { AppUserCompanyRoleID = 5, AppUserCompany = auc5, AppRoleID = 1 };
            AppUserCompanyRole aucr6 = new AppUserCompanyRole() { AppUserCompanyRoleID = 6, AppUserCompany = auc6, AppRoleID = 1 };

            List<AppUser> users = new List<AppUser> { stanley, jerson, philip, samantha };
            List<AppUserCompany> appUserCompanies = new List<AppUserCompany> { auc1, auc2, auc3, auc4, auc5, auc6 };
            List<AppUserCompanyRole> appUserCompanyRoles = new List<AppUserCompanyRole> { aucr1, aucr2, aucr3, aucr4, aucr5, aucr6 };
            var ids = new List<int> { 2088, 38, 1926, 2059, 2058, 1925, 2097, 2061, 2072, 2064 };

            var result = from au in users
                         let appUserIDs = (from auc in appUserCompanies
                                           join aucr in appUserCompanyRoles on auc.AppUserCompanyID equals aucr.AppUserCompany.AppUserCompanyID
                                           where auc.CompanyID == 2 && aucr.AppRoleID == 4 && auc.AppUser.AppUserID == au.AppUserID
                                           select auc.AppUser.AppUserID).Distinct()
                         where  appUserIDs.Count() == 0  && ids.Contains(au.AppUserID)
                         select au;