LINQ where子句中的三元运算符

Question

我使用linq连接多个表并编写复杂的查询.这里,当我将有"0"的任何参数即CategoryId,GameId,LimitVariantId,这意味着用户已选择了"所有",从接口.

我的Sql查询,当我将参数值传递给大于'0'时:

select * from dbo.GameCombinations gc
inner join dbo.StakeBuyInByStakeCategories sbsc
on sbsc.StakeBuyInByStakeCategoryId = gc.StakeBuyInByStakeCategoryId
inner join dbo.GameTables gt
on gc.GameCombinationId = gt.GameCombinationId
where gc.CurrencyId=1 and gc.GameTypeId=2
and sbsc.StakeBuyInId=gt.BuyIn
and gc.CategoryId=4
and gc.GameId=7
and gc.LimitVariantId=23
and gc.StakeCategoryId in (3,5,6)

当我将传递CategoryId 0然后我的Sql查询将是:

select * from dbo.GameCombinations gc
inner join dbo.StakeBuyInByStakeCategories sbsc
on sbsc.StakeBuyInByStakeCategoryId = gc.StakeBuyInByStakeCategoryId
inner join dbo.GameTables gt
on gc.GameCombinationId = gt.GameCombinationId
where gc.CurrencyId=1 and gc.GameTypeId=2
and sbsc.StakeBuyInId=gt.BuyIn
--and gc.CategoryId=4
and gc.GameId=7
and gc.LimitVariantId=23
and gc.StakeCategoryId in (3,5,6)

所以我不需要在where子句中包含那些字段.为此我写了以下LINQ:

ProviderDB db = new ProviderDB();
try
{
    IQueryable<dynamic> query;

    if (StakeCategoryIdsByStakeBuyIn != null)
    {
        query = (from gc in db.GameCombinations.Where(x => x.CurrencyId == CurrencyId && x.GameTypeId == GameTypeId
                            && CategoryId <= 0 ? true : x.CategoryId == CategoryId
                            && GameId <= 0 ? true : x.GameId == GameId
                            && LimitVariantId <= 0 ? true : x.LimitVariantId == LimitVariantId
                            && StakeCategoryIdsByStakeBuyIn.Contains(x.StakeCategoryId)
                        )
                 join sbsc in db.StakeBuyInByStakeCategories
                 on gc.StakeBuyInByStakeCategoryId equals sbsc.StakeBuyInByStakeCategoryId
                 join gt in db.GameTables
                 on gc.GameCombinationId equals gt.GameCombinationId
                 join gx in db.Games
                 on gc.GameId equals gx.GameId into joined
                 from gx in joined.DefaultIfEmpty()
                 where gt.BuyIn == sbsc.StakeBuyInId
                 select new
                 {
                     GameTableId = gt.GameTableId,
                     Description = gt.Description,
                     BuyIn = gt.BuyIn,
                     Table = gx.GameName,
                     MaxAllowPlayer = gt.MaxAllowPlayer
                 }).Distinct();
    }
    else
    {
        query = (from gc in db.GameCombinations.Where(x => x.CurrencyId == CurrencyId && x.GameTypeId == GameTypeId
                              && CategoryId == 0 ? true : x.CategoryId == CategoryId
                              && GameId == 0 ? true : x.GameId == GameId
                              && LimitVariantId == 0 ? true : x.LimitVariantId == LimitVariantId
                              && StakeCategoryIdsByStakeBuyIn == null
                        )
                 join sbsc in db.StakeBuyInByStakeCategories
                 on gc.StakeBuyInByStakeCategoryId equals sbsc.StakeBuyInByStakeCategoryId
                 join gt in db.GameTables
                 on gc.GameCombinationId equals gt.GameCombinationId
                 join sb in db.StakeBuyIns
                 on gt.BuyIn equals sb.StakeBuyInId
                 join gx in db.Games
                 on gc.GameId equals gx.GameId into joined
                 from gx in joined.DefaultIfEmpty()
                 where gt.BuyIn == sbsc.StakeBuyInId
                 select new
                 {
                     GameTableId = gt.GameTableId,
                     Description = gt.Description,
                     BuyIn = sb.StakeBuyInValue,
                     Table = gx.GameName,
                     MaxAllowPlayer = gt.MaxAllowPlayer
                 }).Distinct();
    }

但这将返回我的数据库中的所有字段.那么任何人都可以帮我在LINQ中用三元条件编写这些查询,这将返回我的过滤字段的记录吗？

Answer 1

使用 Linq to SQL（通常使用 LINQ），您可以以Where编程方式添加条件，例如：

var query = db.GameCombinations.Where(x => x.CurrencyId == CurrencyId && x.GameTypeId == GameTypeId);

if (CategoryId > 0)
{
    query = query.Where(x => x.CategoryId == CategoryId);
}

等等。

此外，最好使用“类型推断”（使用var关键字）而不是dynamic，你不会得到智能感知dynamic

[编辑] Linq to SQL 提供程序将Where在转换为 SQL 时对所有条件进行分组