Linq查询，如果搜索项为null或为空，则返回所有记录(Linq query that returns all records if the search item is null or empty

Linq查询，如果搜索项为null或为空，则返回所有记录(Linq query that returns all records if the search item is null or empty)

我不太熟悉linq，我正在努力消除在代码中复制一堆linq查询的需要。 我希望如果字符串description值为null或为空，我可以修改此linq查询以返回整页结果。 目前它在该场景中没有返回任何结果。

所以基本上我想要这个查询......

return _entities.Schedules.Where(s => s.Description.ToLower().Contains(description.ToLower()))) .OrderByWithDirection(x => x.Description, dir) .Skip((pageNumber - 1) * pageSize) .Take(pageSize) .ToList();

...如果description为null或为空，也返回此查询的结果。

return _entities.Schedules.OrderByWithDirection(x => x.Description, dir) .Skip((pageNumber - 1) * pageSize) .Take(pageSize) .ToList();

I'm not very well versed in linq and I'm trying to eliminate the need to duplicate a bunch of linq queries in my code. I'm hoping that I can modify this linq query to return a full page of results if the value of the string description is null or empty. Currently it returns no results in that scenario.

So basically I want this query...

return _entities.Schedules.Where(s => s.Description.ToLower().Contains(description.ToLower()))) .OrderByWithDirection(x => x.Description, dir) .Skip((pageNumber - 1) * pageSize) .Take(pageSize) .ToList();

...to also return the results that this query would if description were null or empty.

return _entities.Schedules.OrderByWithDirection(x => x.Description, dir) .Skip((pageNumber - 1) * pageSize) .Take(pageSize) .ToList();

最满意答案

LINQ是可组合的，因此您可以非常简单地执行此操作：

IQueryable<Schedule> results = _entities.Schedules; // Only filter on description if a search term has been given if (!string.IsNullOrEmpty(description)) { results = results.Where(s => s.Description.ToLower().Contains(description.ToLower()))) } return results.OrderByWithDirection(x => x.Description, dir) .Skip((pageNumber - 1) * pageSize) .Take(pageSize) .ToList();

LINQ is composable, so you can very simply do this:

IQueryable<Schedule> results = _entities.Schedules; // Only filter on description if a search term has been given if (!string.IsNullOrEmpty(description)) { results = results.Where(s => s.Description.ToLower().Contains(description.ToLower()))) } return results.OrderByWithDirection(x => x.Description, dir) .Skip((pageNumber - 1) * pageSize) .Take(pageSize) .ToList();