如何忽略 LinQ 中的特定条件

Question

我有一个如下的 linq：

var finalist = (from b in GeneralAction.EM().Vwmembersummarydetails
                where selectedPersonId.Contains(b.Id)
                select new GeneralCommonFunctions.MemberDetailSumary
                {
                  Index = 0,
                  ProjectText = string.Join(", ", (from d in GeneralAction.EM().Member_has_properties
                                                   join e in GeneralAction.EM().Properties on d.Property_id equals e.Id
                                                   where d.IsDeleted == 0 && d.Member_id == b.Id && e.ProjectType_id == Convert.ToInt32(projectTypeId)
                                                   select e.Project.Description).Distinct().ToArray()),
                  PropertyText = string.Join(", ", (from f in GeneralAction.EM().Member_has_properties
                                                    join g in GeneralAction.EM().Properties on f.Property_id equals g.Id
                                                    where f.IsDeleted == 0 && f.Member_id == b.Id && g.ProjectType_id == Convert.ToInt32(projectTypeId)
                                                    select g.LotNum).ToArray()),
                  PurchasePrice = GeneralCommonFunctions.GetTotalPurchasePriceByProjectType(b.Id, projectTypeId),
                  Name = b.Name,
                  Email = b.Email,
                  }).AsQueryable();

我想问一下，如何忽略这两个条件：

e.ProjectType_id == Convert.ToInt32(projectTypeId)

g.ProjectType_id == Convert.ToInt32(projectTypeId)

当 projectTypeId 为 null 或 0 时。

Answer 1

要忽略条件，只需使用逻辑或：

(projectTypeId == null || Convert.ToInt32(projectTypeId) == 0 || e.ProjectType_id == Convert.ToInt32(projectTypeId))

要调用不同的函数，请使用三级运算符。请注意，这可能不适用于 Linq to SQL -

(projectTypeId == null ? GeneralCommonFunctions.GetTotalPurchasePrice(b.Id) : GeneralCommonFunctions.GetTotalPurchasePriceByProjectType(b.Id, projectTypeId))

Answer 2

我是投反对票的人。 SO的原因是寻找真正难以找到的解决方案。但是好像你在发帖之前都没有尝试过。

用你自己的话解决办法——

e.ProjectType_id == Convert.ToInt32(projectTypeId)

g.ProjectType_id == Convert.ToInt32(projectTypeId)

当 projectTypeId 为 null 或 0 时。

所以，把那个英文句子转换成代码。

&& e.ProjectType_id == Convert.ToInt32(projectTypeId)

会变成-

&& ((e.ProjectType_id != null && e.ProjectType_id != "0") ? e.ProjectType_id == Convert.ToInt32(projectTypeId) : true)

然后您可以像@netmage 提到的那样对其进行更多优化-

(projectTypeId == null || Convert.ToInt32(projectTypeId) == 0 || e.ProjectType_id == Convert.ToInt32(projectTypeId))

同样，

projectTypeId 为 null 时如何调用 GeneralCommonFunctions.GetTotalPurchasePrice()，projectTypeId 不为 null 时如何调用 GeneralCommonFunctions.GetTotalPurchasePriceByProjectType()。

类似地变成-

PurchasePrice = projectTypeId = null ? GeneralCommonFunctions.GetTotalPurchasePrice(...) : GeneralCommonFunctions.GetTotalPurchasePriceByProjectType(b.Id, projectTypeId),