I got this error when I tried to make a method to return all users which have no users
Severity Code Description Project File Line Suppression State
Error (active) CS0029 Cannot implicitly convert type ‘System.Collections.Generic.List<<anonymous type: decimal SSN, string FullName>>’ to ‘System.Collections.Generic.List’

I have two classes
first class

public partial class User
{
    public int Id { get; set; }

    public string? FullName { get; set; }

    public string? UserName { get; set; }

    public string? Password { get; set; }

    public string? Role { get; set; }

    public decimal? EmpId { get; set; }

    public DateTime? CreatedDate { get; set; }

    public DateTime? EditedDate { get; set; }

    public virtual Employee? Emp { get; set; }

}

second class
public partial class Employee
{
public decimal Ssn { get; set; }

public int? EmpCode { get; set; }

public string? EmpFirstName { get; set; }

public string? EmpSecondName { get; set; }

public string? EmpLastName { get; set; }

public virtual User? User { get; set; }

}
and I want to create a method to return all users which have no users

I wrote this code in EmployeesEF class

public List<string> GetAllEmpsIsNotUser()
{
    try
    {

        var query = from emp in db.Employees
               join user in db.Users on emp.Ssn equals user.EmpId into userGroup
               from u in userGroup.DefaultIfEmpty()
               where !db.Users.Any(u => u.EmpId == emp.Ssn)
               select new
               {
                   SSN = emp.Ssn,
                   FullName = emp.EmpFirstName + " " + emp.EmpSecondName + " " + emp.EmpLastName
               };

        return query.ToList();
    }
    catch
    {
        return new List<string>();

    }
}