如何在LINQ中使用join獲取項目列表？

Question

我正在研究現有的解決方案。 我有兩個實體

  public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Email { get; set; }
        public DateTime? DOB { get; set; }
        private List<long> _accounts = new List<long>();

        [Display(Name = "Account No")]
        public List<long> Accounts
        {
            get { return _accounts; }
            set { _accounts = value; }
        }
        [Display(Name = "Account No")]
        public string AccountId
        {
            get { return string.Join(",", _accounts); }
            set { _accounts = value != null ? value.Split(',').Where(s=>!string.IsNullOrWhiteSpace(s)).Select(s => Convert.ToInt64(s.Trim())).ToList() : new List<long>(); }
        }

    }

     public class Account
    {
        public long Id { get; set; }
        public string AccountName { get; set; }
        public string AccountNo { get; set; }

    }

還有一個ViewModel

  public class UserAccountViewModel
    {
        public long AccountId { get; set; }
        public string AccountNo { get; set; }            
        public int UserId { get; set; }
        public string UserName { get; set; }

    }

現在，如何從這些實體中獲取List<UserAccountViewModel> ？

Answer 1

var UserAccountViewModel = (from Account in list1
             join UserAccountViewModel in list2
             on Account .AccountNo equals UserAccountViewModel.AccountNo 
             select new { UserAccountViewModel }).ToList();

希望對您有幫助。 或根據建議提高性能

var query = dataContext.UserAccountViewModel 
            .Include(o => o.Account)
            .Where(t=> t.AccountNo  == t.Account.AccountNo).ToList();

Answer 2

如果您有兩個要創建列表的帳戶和用戶列表，則可以使用：

var userAccount = (from account in list1
         join user in list2
         on account.Id.ToString() equals user.AccountIds
         select new UserAccountViewModel 
        { 
         AccountId = account.Id,
         AccountNo = account.AccountNo,
         UserName = user.Name,
         UserId = user.Id
        }).ToList();

Answer 3

最后我得到了答案，就像下面的例子：

        var users = new List<User>{
        new User{Id=1 ,Name="Test1",Email="test1@ds.com",DOB=DateTime.Now,AccountId ="1"},
        new User{Id=2 ,Name="Test2",Email="test2@ds.com",DOB=DateTime.Now,AccountId ="2"},
        new User{Id=3 ,Name="Test3",Email="test3@ds.com",DOB=DateTime.Now,AccountId ="3,4"}
        };
        var accunts = new List<Account>
        {
            new Account {Id=1,AccountName = "A",AccountNo = "1"},
            new Account {Id=2,AccountName = "B",AccountNo = "2"},
            new Account {Id=3,AccountName = "C",AccountNo = "3"},
            new Account {Id=4,AccountName = "D",AccountNo = "4"},
        };

        var userAccounts = (from u in users
                   from a in accunts
                   where u.Accounts.Contains(a.Id)
                   select new UserAccountViewModel
                   {
                       AccountNo = a.AccountNo,
                       AccountId = a.Id,
                       UserId = u.Id,
                       UserName = u.Name
                   }).ToList();