Question

我正在使用以下Linq表达式执行选择查询：

Table<Tbl_Movement> movements = context.Tbl_Movement;
var query = from m in movements
            select new MovementSummary
            {
                Id = m.DocketId,
                Created = m.DateTimeStamp,
                CreatedBy = m.Tbl_User.FullName,
                DocketNumber = m.DocketNumber,
                DocketTypeDescription = m.Ref_DocketType.DocketType,
                DocketTypeId = m.DocketTypeId,
                Site = new Site()
                {
                    Id = m.Tbl_Site.SiteId,
                    FirstLine = m.Tbl_Site.FirstLine,
                    Postcode = m.Tbl_Site.Postcode,
                    SiteName = m.Tbl_Site.SiteName,
                    TownCity = m.Tbl_Site.TownCity,
                    Brewery = new Brewery()
                    {
                        Id = m.Tbl_Site.Ref_Brewery.BreweryId,
                        BreweryName = m.Tbl_Site.Ref_Brewery.BreweryName
                    },
                    Region = new Region()
                    {
                        Description = m.Tbl_Site.Ref_Region.Description,
                        Id = m.Tbl_Site.Ref_Region.RegionId
                    }
                }
            };

我也将IFilter类传递给执行此选择的方法。

public interface IJobFilter
{
    int? PersonId { get; set; }
    int? RegionId { get; set; }
    int? SiteId { get; set; }
    int? AssetId { get; set; }
}

如何将这些参数添加到我的SQL表达式中？我希望在另一种方法中完成此操作，因为过滤将在多个存储库中重复使用。

不幸的是，当我query.Where时，它已成为IQueryable<MovementSummary>。我假设它已成为这个，因为我正在返回IEnumerable<MovementSummary>。我刚刚开始学习LINQ，所以要温柔。

答案：

private IQueryable<Tbl_Docket> BuildQuery(IQueryable<Tbl_Docket> movements, IMovementFilter filter)
{
   if (filter != null)
   {
      if (filter.PersonId.HasValue) movements = movements.Where(m => m.UserId == filter.PersonId);
      if (filter.SiteId.HasValue) ...
   }
   return movements;
}

如下所示：

var query = from m in this.BuildQuery(movements, filter)
            select new... {}

Answer 1

你必须在激活select语句之前调用where语句，例如：

IQueryable<Tbl_Movement> movements = context.Tbl_Movement;
if (filter != null)
{
   if (filter.PersonId != null) movements = movements.Where(m => m....PersonId == filter.PersonId);
   if (filter.RegionId != null) movements = movements.Where(m => m....RegionId == filter.RegionId);
   if (filter.SiteId != null) movements = movements.Where(m => m...SiteId == filter.SiteId);
   if (filter.AssetId != null) movements = movements.Where(m => m...AssetId == filter.AssetId);
}

 var query = m from movements...

与使用此IFilter类相反，您可能需要考虑Fluent Pipe-based Repository结构，例如：

var movements = new MovementsPipe()
    .FindSiteId(1)
    .FindAssetIds(1, 2, 3)
    .FindRegionId(m => m > 10)
    .ToMovementSummaryList();

希望这会有所帮助。如果您有任何问题，请告诉我。

在以下方案中，如何使用原始Linq-to-SQL对象添加where过滤器

1 个答案: