C＃LINQ可以为空。内联空值检查

Question

I am attempting to do the following

List<JobPhase> jobPhases = new JobPhaseDao().findAll();
jobPhases.Remove(jobPhases.Where(m => m.Name.Contains("Pre")).First());

Is there an elegant way to do an inline null check here such that if the list find any matches I can remove nothing?

Thanks

Answer 1

List.Remove appears to already support this behavior: pass a null as the parameter, and it should remove nothing.

To avoid an exception when your .Where call returns no matches, use FirstOrDefault() instead of First() .

Note that if you expect only one item to match the Where predicate, you should use SingleOrDefault rather than First .

That said, it's not entirely clear what you're trying to do: if you have multiple JobPhases that contain "Pre" in the name, you are somewhat-arbitrarily removing one of them from the list. Are you instead trying to remove all matching JobPhases? If so, you should explore a different approach, such as using RemoveAll() . For example:

List<JobPhase> jobPhases = new JobPhaseDao().findAll();
jobPhases.RemoveAll(jobPhases.Where(m => m.Name.Contains("Pre")));

Answer 2

List<JobPhase> jobPhases = new JobPhaseDao().findAll()
    .Where(m => !m.Name.Contains("Pre"));