我有以下查询:
from p in dataContext.Repository<IPerson>()
join spp1 in dataContext.Repository<ISportsPerPerson>() on p.Id equals spp1.PersonId
join s1 in dataContext.Repository<ISports>() on spp1.SportsId equals s1.Id
join spp2 in dataContext.Repository<ISportsPerPerson>() on p.Id equals spp2.PersonId
join s2 in dataContext.Repository<ISports>() on spp2.SportsId equals s2.Id
where s1.Name == "Soccer" && s2.Name == "Tennis"
select new { p.Id };
选择所有踢足球和网球的人 在运行时,用户可以选择要添加到查询的其他标签,例如:“Hockey”。现在我的问题是,我怎么能动态添加“曲棍球”到查询?如果将“Hockey”添加到查询中,它将如下所示:
from p in dataContext.Repository<IPerson>()
join spp1 in dataContext.Repository<ISportsPerPerson>() on p.Id equals spp1.PersonId
join s1 in dataContext.Repository<ISports>() on spp1.SportsId equals s1.Id
join spp2 in dataContext.Repository<ISportsPerPerson>() on p.Id equals spp2.PersonId
join s2 in dataContext.Repository<ISports>() on spp2.SportsId equals s2.Id
join spp3 in dataContext.Repository<ISportsPerPerson>() on p.Id equals spp3.PersonId
join s3 in dataContext.Repository<ISports>() on spp3.SportsId equals s3.Id
where s1.Name == "Soccer" && s2.Name == "Tennis" && s3.Name == "Hockey"
select new { p.Id };
如果查询是动态构建的,最好是:
private void queryTagBuilder(List<string> tags)
{
IDataContext dataContext = new LinqToSqlContext(new L2S.DataContext());
foreach(string tag in tags)
{
//Build the query?
}
}
任何人都知道如何正确设置它? 提前谢谢!
答案 0 :(得分:3)
在实际执行LINQ查询之前,不会对其进行解析。所以你可以做这样的事情:
var q = from r in ctx.records
/* Do other stuff */
select r;
if (!string.IsNullOrEmpty(search)) {
q = from r in q
where r.title == search
select r;
}
if (orderByName) {
q = q.OrderBy(r => r.name);
}
/* etc */
这将创建一个正在执行的SQL语句。
针对您的具体问题:联接使其有点复杂,但我认为您可以加入其他“动态”查询。
所以你最终会得到这样的东西:
var baseQ = from p in dataContext.Repository<IPerson>()
select p;
foreach(var tag in tags) {
baseQ = from p in baseQ
join spp1 in dataContext.Repository<ISportsPerPerson>() on p.Id equals spp1.PersonId
join s1 in dataContext.Repository<ISports>() on spp1.SportsId equals s1.Id
where s1.name == tag
select p;
}
/* If you have defined your relations correct, simplify to something like this.
Does not actually work because of SportsPerPerson probably has multiple sports: */
foreach(var tag in tags) {
baseQ = baseQ.Any(p => p.SportsPerPerson.Sports.Name == tag);
}
var resultQ = from p in baseQ
select new { p.Id };
答案 1 :(得分:2)
我和我的同事找到了解决方案,我们重构了查询,以便它能正常工作。我们现在使用以下查询来检索正确的结果集:
var query = dataContext.Repository<ILead>();
foreach (var tag in tags)
{
String tagName = tag;
query = query.Where(l => dataContext.Repository<ISportsPerPerson>()
.Any(tpl => tpl.PersonId.Equals(l.Id) && tpl.Sports.Name.Equals(tagName)));
}
// Do something with query resultset :]