using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Transactions;   // the code is showing an error in this line

class Program
{
  static void Main(string[] args)
  {
    try
    {
       string connectString = "Initial Catalog=AdventureWorks;
                               Data Source=SQLSERVER01;
                               User id =user;password=password";
       SqlConnection con = new SqlConnection();
       con.ConnectionString = connectString;

       con.Open();

       SqlTransaction tr = null;
       tr = con.BeginTransaction();

       SqlCommand cmd = new SqlCommand("INSERT INTO sunny1(name, id, city, phone, pincode) VALUES ('sandy', 01441, 'abc', 'phone', 122001)", con, tr);
       cmd.ExecuteNonQuery();
       tr.Commit();

       Console.WriteLine("transaction completed ");
    }
    catch (SqlException e)
    {
       tr.Rollback();
       Console.WriteLine("teansaction not completed " + e.Message);
    }
    catch (System.Exception ex)
    {
       Console.WriteLine("system error " + ex.Message);
    }
    finally
    {
       cn.Close();
    }

    Console.ReadLine();
 }
}

SqlConnection con = new SqlConnection();
   con.ConnectionString = connectString;

   con.Open();

   SqlTransaction tr = null;
   tr = con.BeginTransaction();

   SqlCommand cmd = new SqlCommand("INSERT INTO sunny1(name, id, city, phone, pincode) VALUES ('sandy', 01441, 'abc', 'phone', 122001)", con, tr);
   cmd.ExecuteNonQuery();
   tr.Commit();

using(SqlConnection con = new SqlConnection(connectString))
   {
      SqlTransaction tr = con.BeginTransaction();

      using(SqlCommand cmd = new SqlCommand("....", con, tr))
      {
         con.Open();
         cmd.ExecuteNonQuery();
         tr.Commit();
         con.Close();
      }
   }

using System.Transactions;

con.Open();

   SqlTransaction tr = null;
   tr = con.BeginTransaction();

   SqlCommand cmd = new SqlCommand("INSERT INTO sunny1(name, id, city, phone, pincode) VALUES ('sandy', 01441, 'abc', 'phone', 122001)", con, tr);
   cmd.ExecuteNonQuery();
   tr.Commit();

con.Open();

   SqlCommand cmd = new SqlCommand("INSERT INTO sunny1(name, id, city, phone, pincode) VALUES ('sandy', 01441, 'abc', 'phone', 122001)", con);
   cmd.ExecuteNonQuery();