c# - 将 LINQ 表达式从 C# 转换为 VB.NET 在 Group by 中引发异常

Question

我在 C# 中有以下 Linq 表达式，它运行良好:

from c3 in equipment.Measures
where c3.IdEq == eq.IdEq && !(c3.magnitudeId == null || c3.magnitudeId.Trim() == string.Empty)
group c3 by c3.magnitudeId into cgroup
                  select new
                  {
                      MagnitudeID = cgroup.Key,
                      MaxDate = cgroup.Max(x => x.NextDate)
                  }

现在我尝试将其转换为 VB.NET 表示法:

From c3 In equipment.Measures
Where c3.IdEq = eq.IdEq AndAlso Not (String.IsNullOrWhiteSpace(c3.magnitudeId))
Group c3 By c3.magnitudeId Into grp = Group
          Select New With
          {
            .MagnitudeID = grp.Key,
            .MaxDate = grp.Max(Function(x) x.NextDate)
          }

...但我收到一条错误消息:

'key' is not a member of 'System.Collection.Generics.IEnumberable(Of ...)'

Answer 1

尝试以下操作(另请注意，为了等效，您需要在 VB 中使用“Key”关键字):

From c3 In equipment.Measures
    Where c3.IdEq = eq.IdEq AndAlso Not (c3.magnitudeId Is Nothing OrElse c3.magnitudeId.Trim() = String.Empty)
    Group c3 By c3.magnitudeId Into cgroup = Group
    Select New With {
        Key .MagnitudeID = magnitudeId,
        Key .MaxDate = cgroup.Max(Function(x) x.NextDate)
    }

如果 C# 和 VB 团队能够稍微协调一下就好了，因为 C# 和 VB 之间 LINQ 的一些差异非常令人费解。