c# - 在 C# 中使用 EF 查询中的多个 Where 子句

Question

我有两个 IQueryable 查询:

IQueryable<Ad> list1 = db.Ads.Where(x=>x.isModerated == true);
IQueryable<Ad> list2;

if(something == true)
{
    list2 = list1.Where(x=>x.TypeId == 2) 
    // is it going to be the same as query below?
    IQueryable<Ad> list1 = db.Ads.Where(x=>x.isModerated == true && x.TypeId == 2)   
}

如果我想使用 OR (||) 运算符获取数据怎么办是相同的情况。

而且我相信在我想要迭代此查询之前，这将是一次数据库调用。正确的？

Answer 1

is it going to be the same as query below?

是

and what if I would like to get a data using OR (||) operator is the same scenario.

这样做的资源成本要低得多:

IQueryable<Ad> list1 = db.Ads.Where(x=>x.isModerated);
IQueryable<Ad> list2;

if(something == true)
{
    list2 = list1.Where(x=>x.TypeId == 2) 
}
else 
{
    list2 = db.Ads.Where(x=>x.isModerated  || x.TypeId == 2)  
}

但是如果出于某种原因你不想那样做，你可以这样做:

list2 = list1.Union(db.Ads.Where(x=> x.TypeId == 2)) 

会给你相同的结果集