Question

对于以下查询：

 var result = from sch in schemeDashboard
         join exp in Expenditure on sch.schemeId equals exp.SchemeCode
         into SchExpGroup
         where sch.SectorDepartmentId == selectedDepartmentId &&
               sch.YearCode == StateManager.CurrentYear
         orderby sch.ADPId
         select new
         {
            ModifiedAmounts = SchExpGroup.Select(a => a.ModifiedAmounts),
            ProjectName = sch.schemeName,
            ADPNo = sch.ADPId,
            Allocation = sch.CurrentAllocation,
            Expenditures = from expend in SchExpGroup
                           where expend.YearCode == StateManager.CurrentYear && 
                                 expend.DepartmentId == selectedDepartmentId &&
                                 InvStatus.Contains(expend.Status)
                         orderby expend.ADPId
                         group expend by expend.InvoiceId
          };

我想在条件上过滤上述查询，以便结果只提供那些＆＃34; ModifiedAmounts＆＃34;不是空的。我尝试过如下：

 if (rbList2.SelectedIndex == 6)
{
 result = result.Where(a => a.ModifiedAmounts != null));
}

但这会产生错误：

无法比较类型的元素＆＃39; System.Collections.Generic.IEnumerable`1＆＃39 ;.只有原始类型，支持枚举类型和实体类型。

任何建议，因为我丢失了如何重新定义过滤后的查询。

Answer 1

我认为问题是ModifiedAmounts永远不会为null。选择将返回一个空列表。除非SchExpGroup为null，否则您将获得空引用异常。

尝试将代码更改为

result = result.Where(a => a.ModifiedAmounts.Any());

Answer 2

 if (rbList2.SelectedIndex == 6)
{
 result = result.Where(a => a.!ModifiedAmounts.Any());
}

如何在Linq查询中比较IEnumerable <string>为null

2 个答案: