Question

我有一个像这样的对象

public class Employee
{
    public int EmployeeId { get; set; }
    public string Name { get; set; }

    public IList<Employee> Employees{ get; set; }
}

我想要做的是在一个集合中选择所有员工以及父员工。我希望将父项作为分页集合中的第一项。现在我正在做这样的事情

Employee emp = getEmployeeFromService();
var allEmps = new List<Employee>();
allEmps.Add(emp);
allEmps.AddRange(emp.Employees);

var pagedEmployees= (from e in allEmps select e).Skip(offset).Take(pageSize);

使用单个linq语句有更好的方法吗？

Answer 1

像这样：

var pagedEmployees = new [] { emp }.Concat(allEmps).Skip(offset).Take(pageSize);

Answer 2

查看此问题：How to use LINQ to select all descendants of a composite object。

Answer 3

获取员工名单：

 employees.Concat(employees.SelectMany(x => x.Employees)).Skip(offset).Take(pageSize);

示例（输出7）：

public class Employee
{
    public Employee()
    {

    }

    public Employee(int count)
    {
        Employees = new List<Employee>();
        List<Employee> list = Employees as List<Employee>;
        for (int i = 0; i < count; i++)
        {
            list.Add(new Employee());               
        }
    }

    public IEnumerable<Employee> Employees { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        IEnumerable<Employee> employees = new Employee[]
                                            {
                                                new Employee(3),
                                                                new Employee(2)
    };


        IEnumerable<Employee> enumerable = employees.Concat(employees.SelectMany(x => x.Employees));


        Console.WriteLine(enumerable.Count());
        Console.Read();
    }
}

当linq与type相同时，选择父级和子级

3 个答案: