linq - 仅几百条记录的LINQ性能问题

Question

在以下代码中，我在使我的页面减速的行上进行了注释。我做了一些速度测试，以发现CONTAINS LINQ表达式是问题所在。

有谁知道如何使用其他方法来更改这条线以提高效率。我也很好奇为什么它这么慢。

任何想法(预先感谢):

    var allWaste = _securityRepository.FindAllWaste(userId, SystemType.W);
    var allWasteIndicatorItems = _securityRepository.FindAllWasteIndicatorItems();

    // First get all WASTE RECORDS
    var searchResults = (from s in allWaste
                         join x in allWasteIndicatorItems on s.WasteId equals x.WasteId
                         where (s.Description.Contains(searchText)
                         && s.Site.SiteDescription.EndsWith(searchTextSite)
                         && (s.CollectedDate >= startDate && s.CollectedDate <= endDate))
                         && x.EWC.EndsWith(searchTextEWC)
                         select s).Distinct();

    var results = searchResults.AsEnumerable();

    if (hazardous != "-1") 
    {
        // User has requested to filter on Hazardous or Non Hazardous only rather than Show All
        var HazardousBoolFiltered = (from we in _db.WasteIndicatorItems
        .Join(_db.WasteIndicators, wii => wii.WasteIndicatorId, wi => wi.WasteIndicatorId, (wii, wi) => new { wasteid = wii.WasteId, wasteindicatorid = wii.WasteIndicatorId, hazardtypeid = wi.HazardTypeId })
        .Join(_db.HazardTypes, w => w.hazardtypeid, h => h.HazardTypeId, (w, h) => new { wasteid = w.wasteid, hazardous = h.Hazardous })
        .GroupBy(g => new { g.wasteid, g.hazardous })
        .Where(g => g.Key.hazardous == true && g.Count() >= 1)
                                     select we).AsEnumerable(); // THIS IS FAST

        // Now join the 2 object to eliminate all the keys that do not apply
        if (bHazardous)
            results = (from r in results join x in HazardousBoolFiltered on r.WasteId equals x.Key.wasteid select r).AsEnumerable(); //This is FAST
        else
            results = (from r in results.Where(x => !HazardousBoolFiltered
                .Select(y => y.Key.wasteid).Contains(x.WasteId)) select r).AsEnumerable(); // This is DOG SLOW 10-15 seconds !--- THIS IS SLOWING EXECUTION by 10 times --!


    }


    return results.AsQueryable();

Answer 1

尝试Any(MSDN)

尝试这个:

results = (from r in results
    .Where(x => !HazardousBoolFiltered
        .Any(y => y.Key.wasteid == r.WasteId)))
    .AsEnumerable()

或 Count:

results = (from r in results
    .Where(x => HazardousBoolFiltered
        .Count(y => y.Key.wasteid == r.WasteId) == 0))
    .AsEnumerable()