c# - Linq join, group, count where count 大于 value

Question

我有以下 linq 表达式，可让我加入两个表，按 a 对它们进行DSCID分组，然后获取分组值的计数：

var qryGeoApppendCount =
              from a in append
              join g in geo
              on a.Field<string>("RNO")
              equals g.Field<string>("RNO")
              group g by g.Field<int>("DSCID") into appendGeo
              select new
              {
                DscId = appendGeo.Key,
                DscIdCount = appendGeo.Count()
              };

我需要通过仅选择大于 1 的计数来更进一步。我尝试了这样的事情：

select new
{
    DscId = appendGeo.Key,
    DscIdCount = appendGeo.Count(n => n.Count > 1)
};

但这没有用。我需要能够在qryGeoAppendQuery返回计数 > 1 的记录时抛出错误，因此理想情况下，查询将包含在 if 语句中。

Answer 1

var qryGeoApppendCount =
              (from a in append
              join g in geo
              on a.Field<string>("RNO")
              equals g.Field<string>("RNO")
              group g by g.Field<int>("DSCID") into appendGeo
              select new
              {
                DscId = appendGeo.Key,
                DscIdCount = appendGeo.Count()
              })
              .Where(a => a.DscIdCount > 1);

Answer 2

你就不能...

select new
{
  DscId = appendGeo.Key,
  DscIdCount = appendGeo.Where(n => n.Count > 1).Count()
};

或者如果你只是想知道是否存在...

select new
{
  DscId = appendGeo.Key,
  ThrowException = appendGeo.Any(n => n.Count > 1)
};

Answer 3

var qryGeoApppendCount =
          from a in append
          join g in geo
          on a.Field<string>("RNO")
          equals g.Field<string>("RNO")
          group g by g.Field<int>("DSCID") into appendGeo
          where appendGeo.Count() > 1
          select new
          {
            DscId = appendGeo.Key,
            DscIdCount = appendGeo.Count()
          };

你不能在选择之前添加一个where子句吗？它在我的示例中有效，但我不确定没有看到数据。

Answer 4

"SELECT  [SubsNumber], sum([Usage_MB])/1024 as GB FROM [VASCDR].[dbo].[nrmSubsDailyMBUsage] where SubsNumber ='" + textBox1.Text.Trim() + "'" group by [SubsNumber] ;

是如何使用 c#