英文:
Using Orderby with conditional?
问题
你好，我正在尝试编写一个查询，按日期排序，但如果有 due_date，则使用该日期，如果没有 due_date，则使用 sample_date。这是我尝试的代码，但是不正确。
是否有办法在 orderby 或 thenby 中使用条件语句呢？
期望结果：
实际结果：
英文:
Hello I am trying to get a query to order by dates but if there is a due_date to use that if there isn't a due_date it needs to use sample_date. This is what i tried but it isnt correct.
is there a way to use a conditional in a orderby or a thenby or no?
expecting:
what i got:
答案1
得分: 2
Nulls在升序排序中会出现在第一条记录中。我们可以通过使用coalesce运算符来避免这种情况：
session.Query<ActiveTestListResult>()
.OrderByDescending(x => x.lab_int)
.ThenBy(x => x.due_date ?? x.sample_date)
.ThenBy(x => x.sample_id)
.ThenBy(x => x.batch_id)
英文:
Nulls appear in ascending sorting as first records. We can avoid this by coalesce operator:
session.Query<ActiveTestListResult>()
.OrderByDescending(x => x.lab_int)
.ThenBy(x => x.due_date ?? x.sample_date)
.ThenBy(x => x.sample_id)
.ThenBy(x => x.batch_id)
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