Question

我想使用followng方法按数据表分组。但是我无法选择包含字符串的列

var dtTAConvertList =
    (from dr1 in dtTAConvert.AsEnumerable()
     group dr1 by dr1.Field<DateTime>("SAMPLE_TIME") into g
     select new
     {
         SAMPLE_TIME = g.Key,
         WAIT_CLASS = g.Field<string>("WAIT_CLASS"),          // ==> I get error in this line
         COUNT = Math.Round(g.Sum(h => h.Field<double>("COUNT")) / 15.0, 2),
     });

它引发异常

'IGrouping'不包含'Field'的定义，最佳扩展方法重载'DataRowExtensions.Field（DataRow，string）'需要类型为'DataRow'的接收器

如何选择该数据表中已经存在的字符串列？

Answer 1

由于每个组中Field<string>("WAIT_CLASS")的出现次数很多，因此除了可能要检索第一个出现次数之外，您将必须执行与计数相同的方法：

var dtTAConvertList =
    (from dr1 in dtTAConvert.AsEnumerable()
     group dr1 by dr1.Field<DateTime>("SAMPLE_TIME") into g
     select new {
         SAMPLE_TIME = g.Key,
         WAIT_CLASS = g.First().Field<string>("WAIT_CLASS"),
         COUNT = Math.Round(g.Sum(h => h.Field<double>("COUNT")) / 15.0, 2),
     });

使用LINQ的GroupBy列

1 个答案: