使用 LINQ 获取表中在特定列中具有相同值的所有记录

Question

我正在尝试获取表中具有相同值的列中的所有行。我通过以下方式使用组来工作：

var groupedData = from row in Tab1Model.ExcelGridDataSource.AsEnumerable()
                                            group row by row.Field<string>("A");

        foreach (var group in groupedData)
        {
            if (group.Count() > 1)
            {
                                    //select from each group only the DataRows  
                                    //having a certain value in a second column
                foreach (var dataRow in group)
                {
                    multipleRowsList.Add(dataRow);
                }
            }
        }

我想避免调用 foreach，只获取计数> 1 的组，然后仅获取具有具有特定值的第二列的数据行。谢谢！

Answer 1

试试这个：

var query = from row in excelDataSource 
            group row by row.Field<string>("A") into g 
            select new { Value = g.Key, Rows = g };
var nonZeroRows= from q in query 
                       where q.Rows.Count() > 0 
                       select q.Rows;
// at this point you have an enumerable of enumerables of tablerows.
var list = nonZeroRows.Aggregate(Enumerable.Empty<TableRow>(), 
           (a, b) => a.Concat(b.Where(c => c.Something == true)); // your condition here

Answer 2

谢谢阿塔纳米尔！这是最终的代码，只是想知道您是否有更好的方法。这样做的最终目标是标记输入两次的行之一。

var groupedData = from row in Tab1Model.ExcelGridDataSource.AsEnumerable()
                          group row by row.Field<string>("A")
                          into g
                          select new {Value = g.Key, Rows = g};
        var nonZeroesRows = from q in groupedData
                            where q.Rows.Count() > 1
                            select q.Rows;
        //at this point you have an enumerable of enumerables of tables rows
        var listRows = nonZeroesRows.Aggregate(Enumerable.Empty<DataRow>(),
                                               (a, b) => a.Concat(b.Where(c => c.Field<bool>("Omit Row") == false)));
        //grouped them again and get only the last row from the group wiht a count > 1 
        var doubleRows = from row in listRows
                         group row by row.Field<string>("A")
                         into g
                         where g.Count() > 1
                         select g.Last();

Answer 3

或者也许更好：

            var groupedData = from row in Tab1Model.ExcelGridDataSource.AsEnumerable()
                          group row by row.Field<string>("A")
                          into g
                                            where g.Count() > 1
                          select new {/*Value = g.Key,*/ Rows = g};
        //at this point you have an enumerable of enumerables of tables rows
        var listRows = groupedData.Aggregate(Enumerable.Empty<DataRow>(),
                                               (a, b) => a.Concat(b.Rows.Where(c => c.Field<bool>("Omit Row") == false)));
        //grouped them again and get only the last row from the group wiht a count > 1 
        var doubleRows = from row in listRows
                         group row by row.Field<string>("A")
                         into g
                         where g.Count() > 1
                         select g.Last();