using System;

using System.Data;

using System.Linq;

using System.Data.DataSetExtensions;

using System.Text;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        DataTable table = new DataTable();

        table.Columns.Add("ID");

        table.Columns.Add("ProductName");

        table.Columns.Add("otroCampo");

        table.Columns.Add("campo1");

​

        table.Rows.Add("1", "Chai","1", "01_este");

        table.Rows.Add("2", "Queso Cabrales","1", "02_este");

        table.Rows.Add("3", "Tofu","9", "03_este");

        table.Rows.Add("4", "Tofu","8", "03_este");

        table.Rows.Add("5", "Pizza","10", "01_este");

        char charcr = '\u000A';

        char charcr1 = '\u000D';

        Dictionary <string, string> datos = new Dictionary <string, string> ();

        foreach (DataRow drow in table.Rows)

        {           

            string seccion = drow["campo1"].ToString();

            string fila = string.Empty;

            if(datos.Any(x => x.Key == seccion))

            {

                fila = drow["ID"].ToString()+"|"+

                        drow["ProductName"].ToString()+"|"+

                        drow["otroCampo"].ToString()+"|"+

                        drow["campo1"].ToString()+ charcr1 + charcr;;

                datos[seccion] += fila;

            }

            else

            {

                fila = drow["ID"].ToString()+"|"+

                        drow["ProductName"].ToString()+"|"+

                        drow["otroCampo"].ToString()+"|"+

                        drow["campo1"].ToString()+ charcr1 + charcr;;

                datos.Add(seccion,fila);

            }

            //Console.WriteLine(drow["ProductName"]);

        }

        foreach( var item in datos)

        {

            Console.WriteLine("Datos para: "+item.Key);

            Console.WriteLine(item.Value);

        }                   

    }

}