如何编写 Linq 查询来检查 List 是否具有该 id

Question

我里面有一个列表，里面还有一个列表。如何检查 id 是否存在于任一列表中。

public class Users
{
    public virtual Userid { get; set; }
  
    public virtual List<UserCity> UserCities { get; set; }
}

和

public class UserCity
{
    public virtual UserCityId { get; set; }
  
    public virtual UserCityName { get; set; }
}

如何获得 users 有 Userid =usercityid.

我试过这样的 Linq 查询

List<Users> lstusers = new List<Users>();
lstusers = lstusers
    .Where(x=>x.UserCity.Any(w => w.UserCityId == w.Userid ))
    .ToList();

如果用户有 usercityid 和相同的 userid 我需要得到那些 users.

Answer 1

您的查询有一些错误。试试这个：

// create a dummy list for testing
var lstusers = new List<Users>
{
   new Users {Userid = 1, UserCities = new List<UserCity>{ new UserCity { UserCityId = 1, UserCityName="xxx"} }  }
};
// execute the linq-query
lstusers = lstusers.Where(x => x.UserCities.Any(w => w.UserCityId == x.Userid)).ToList();
// and print the number of users found
Console.WriteLine($"Number of users found: {lstusers.Count}");

如何编写 Linq 查询来检查 List 是否具有该 id

How to write Linq query to check whether List have that id

c#

linq