如何提高搜索这个LINQ查询 [英] How to improve this LINQ query for search
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问题描述
我可以改进这个LINQ查询
Can I improve this LINQ query
var filter = from Dep in deptlist
where (Dep.DepNm.StartsWith(txt1.Text.ToLower())
|| Dep.DepNm.StartsWith(txt1.Text.ToUpper())
||Dep.DepNm.Contains(txt1.Text))
select Dep;
推荐答案
.Text , .Text.ToUpper()
和 .Text.ToLower()
每个项目的固定值; ( ToUpper()
等比较贵);你可以解决这个问题:
Currently, you do a .Text
, .Text.ToUpper()
and .Text.ToLower()
of the fixed value per item; (the ToUpper()
etc being relatively expensive); you can lift this out:
string text = txt1.Text, upper = text.ToUpper(), lower = text.ToLower();
var filter = from Dep in deptlist
where Dep.DepNm.StartsWith(lower) || Dep.DepNm.StartsWith(upper)
|| Dep.DepNm.Contains(text))
select Dep;
我假设这里 .DepNm
很便宜。如果这实际上是一个昂贵的查询属性,您可以使用 let
最小化调用:
I'm assuming here that .DepNm
is trivially cheap. If this is actually an expensive property to query, you can use let
to minimise the calls:
var filter = from Dep in deptlist
let name = Dep.DepNm
where name.StartsWith(lower) || name.StartsWith(upper)
|| name.Contains(text))
select Dep;
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