正確過濾Linq查詢

Question

我有這個查詢從一堆商店中檢索銷售，並將它們作爲列表返回。在我的報告請求屏幕上，用戶可以通過多個ID進行過濾 - ShopOwnerId，ShopRegionId，ShopTypeCode等。

我的查詢的結構是在選定日期之間獲得所有銷售額，然後根據選擇進行過濾。這顯然非常低效。 ：

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，此方法僅在未選擇過濾器的情況下查詢特定日期之間的銷售表。

我堅持的是，用戶可以選擇多個過濾器 - 例如，他們可能會選擇一個regionId和一個ShopTypeCode，所以我不想爲每個if過濾器查詢ctn.ShopSales，因爲如果選擇了多個選項，它將消除以前檢索的值。

有沒有人有任何建議如何解決這個問題？如果需要更多信息，請問！

感謝

Answer 1

當然 - 你不希望每次都從頭開始構建查詢。只需添加額外Where電話有條件：

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(); 

注意查詢不會執行，直到你在最後一行兌現它。