如何在实体框架中按空值排序

Question

有谁知道如何返回最后一个有空值的有序字符串列表？我有这样的事情:

using(var context = new DomainEntities())
{
    var result = context.Users.OrderBy(u => u.LastName).ThenBy(u => u.FirstName);
}

我的问题是这个查询在非空值之前返回空值.

有什么想法吗？

Answer 1

我会做:

using(var context = new DomainEntities())
{
    var result = context.Users.OrderBy(u => u.LastName == null)
                              .ThenBy(u => u.LastName)
                              .ThenBy(u => u.FirstName == null)
                              .ThenBy(u => u.FirstName);
}

...应该产生合理的SQL.

Answer 2

我不知道您是否可以在某处进行一些切换。否则，直截了当的方法可能类似于

    using (var context = new DomainEntities())
    {
        var FirstPart = context.Users.Where(u => u.LastName != null);
        var SecondPart = context.Users.Where(u => u.LastName == null);
        var Result = FirstPart.Union(SecondPart);
    }

Answer 3

var result = context.Users.OrderBy(x => x.FirstName ?? x.LastName);