using System;

using System.Data;

using System.Data.DataSetExtensions;

using System.Xml;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var dt = GetData();

        var dataRows = dt.AsEnumerable();

        Works(dataRows);

        // Fails(dataRows);

    }

​

    public static void Works(EnumerableRowCollection<DataRow> dataRows)

    {

        var grouped = dataRows.GroupBy(

            row => new {

                Name = row["Name"]

            }, 

            (k, g) => new {

                Key = k,

                Group = g.CopyToDataTable()

            });

        foreach(var g in grouped)

        {

            Console.WriteLine("Name:" + g.Key.Name);

            for(var i = 0; i < g.Group.Rows.Count; ++i)

            {

                Console.WriteLine(g.Group.Rows[i]["StartDate"]);

            }

            Console.WriteLine("===");

        }   

    }

    public static void Fails(EnumerableRowCollection<DataRow> dataRows)

    {

        var grouped = dataRows.GroupBy(

            row => new GroupingKey {

                Name = row["Name"]

            }, 

            (k, g) => new {

                Key = k,

                Group = g.CopyToDataTable()

            });

        foreach(var g in grouped)

        {

            Console.WriteLine("Name:" + g.Key.Name);

            for(var i = 0; i < g.Group.Rows.Count; ++i)

            {

                Console.WriteLine(g.Group.Rows[i]["StartDate"]);

            }

            Console.WriteLine("===");

        }       

    }

    public static DataTable GetData()

    {

        DataTable dt = new DataTable();

        dt.Columns.Add("Name");

        dt.Columns.Add("StartDate");

        dt.Columns.Add("EndDate");

        for (var i = 0; i < 10; ++i)

        {

            var row = dt.NewRow();

            row["Name"] = i % 2;

            row["StartDate"] = DateTime.Now;

            row["EndDate"] = DateTime.Now;

            dt.Rows.Add(row);

        }

​

        return dt;

    }

    public class GroupingKey

    {

        public object Name { get; set; }

    }

}