c# - 正确过滤 Linq 查询

Question

我有一个查询，它从一堆商店中检索销售额，并将它们作为列表返回。在我的报告请求屏幕上，用户可以按多个 ID 进行过滤 - ShopOwnerId、ShopRegionId、ShopTypeCode 等。

我的查询的结构是获取选定日期之间的所有销售额，然后根据选择进行过滤。这显然是非常低效的。 :

private List<Sales> GetFilteredListOfSales(Request reportreq)
{
    ModelContainer ctn = new ModelContainer();
    List<ShopSale> shopsSales = new List<shopsale>();

    // If no filters are selected
    //
    if (reportreq.RegionalId == null && reportreq.OwnerId == null && reportreq.ShopTypeCode == null)
    {
        shopsSales = (from sale in ctn.ShopSales
                    where sale.DateSold >= reportreq.FromDate && sale.DateSold <= reportreq.ToDate
                    select sale).ToList();
    }


    // If the regional ID has a value...
    // 
    if (reportreq.RegionalId.HasValue)
    {
        shopsSales = (from sale in ctn.ShopSales
                  where sale.Shop.Owner.RegionalId == reportreq.RegionalId
                    && sale.DateSold >= reportreq.FromDate && sale.DateSold <= reportreq.ToDate
                  select sale).ToList();
    }

    // If the owner ID has a value...
    // 
    if (reportreq.OwnerId.HasValue)
    {
        shopsSales = (from sale in ctn.ShopSales
                  where sale.Shop.OwnerId == reportreq.OwnerId
                    && sale.DateSold >= reportreq.FromDate && sale.DateSold <= reportreq.ToDate
                  select sale).ToList();
    }

    if (!string.IsNullOrEmpty(reportreq.ShopTypeCode))
    {
        shopsSales = (from sale in ctn.ShopSales
                  where sale.Shop.ShopTypeCode.ToUpper().Contains(reportreq.ShopTypeCode.ToUpper())
                    && sale.DateSold >= reportreq.FromDate && sale.DateSold <= reportreq.ToDate
                  select sale).ToList();
    }



    return shopsSales;
}

您可以看到，仅当未选择过滤器时，此方法才会查询特定日期之间的销售表。

我所坚持的是，用户可以选择多个过滤器 - 例如他们可能会选择一个regionId和一个ShopTypeCode，所以我不想为每个if过滤器查询ctn.ShopSales，因为如果选择了多个，它将​​清除以前检索到的值。

有人对如何解决这个问题有任何建议吗？如果需要更多信息，请询问!

谢谢

Answer 1

当然 - 您不想每次都从头开始构建查询。只需添加额外的 Where 有条件调用即可:

var query = ctn.ShopSales.Where(sale => sale.DateSold >= reportreq.FromDate 
                                     && sale.DateSold <= reportreq.ToDate);
if (reportreq.OwnerId.HasValue)
{
    query = query.Where(sale => sale.Shop.OwnerId == reportreq.OwnerId);
}
if (!string.IsNullOrEmpty(reportreq.ShopTypeCode))
{
    query = query.Where(sale.Shop.ShopTypeCode.ToUpper()
                            .Contains(reportreq.ShopTypeCode.ToUpper());
}

var shopSales = query.ToList();

请注意，在您在最后一行中具体化查询之前，该查询不会执行。