using System;

using System.Linq;

using System.Data;

​

public class Program

{

    public static void Main()

    {

         DataTable dt1 = new DataTable();

            dt1.Columns.Add("emp_num", typeof(int));

            dt1.Columns.Add("col1", typeof(string));

            DataRow row1 = dt1.NewRow();

            row1["emp_num"] = 227;

            row1["col1"] = "7";

            dt1.Rows.Add(row1);

​

            DataRow row2 = dt1.NewRow();

            row2["emp_num"] = 155;

            row2["col1"] = "17";

            dt1.Rows.Add(row2);

​

            DataRow row3 = dt1.NewRow();

            row3["emp_num"] = 122;

            row3["col1"] = "3";

            dt1.Rows.Add(row3);

​

            DataRow row4 = dt1.NewRow();

            row4["emp_num"] = 678;

            row4["col1"] = "5";

            dt1.Rows.Add(row4);

​

            DataTable dt2 = new DataTable();

            dt2.Columns.Add("emp_num", typeof(int));

            DataRow row5 = dt2.NewRow();

            row5["emp_num"] = 155;

            dt2.Rows.Add(row5);

​

            DataRow row6 = dt2.NewRow();

            row6["emp_num"] = 678;

            dt2.Rows.Add(row6);

​

            var result = from t1 in dt1.AsEnumerable()

                         join t2 in dt2.AsEnumerable()

                         on t1.Field<int>("emp_num") equals t2.Field<int>("emp_num") into g

                         from foo in g.DefaultIfEmpty()

                         select new

                         {

                              emp_num = t1.Field<int>("emp_num"),

                              col1 = t1.Field<string>("col1"),

                              flag = foo != null ? 1 : 0

                         };

​

            Console.WriteLine("emp_num\tcol1\tflag");

            foreach (var item in result)

            {

                Console.WriteLine("{0}\t{1}\t{2}", item.emp_num, item.col1, item.flag);

            }

    }

}