/// <summary>
        /// ExecuteNonQuery(), ExecuteReader() and ExecuteScaler() supports functionality for synchronous execution.
        /// The connection string for these process will be same as you will provide for rest of example.
        /// </summary>
        public void synchronousExample()
        {
            SqlConnection con = new SqlConnection();          //Create an SqlConnection object.
            //Create a connection string. For Synchronous it will same as usual you use but for asynchronous an addition keyword is added in connection string.
            string connString = "Data Source=AA-PC;User Id=sa;Password=bbbb;Initial Catalog=Workbook";
            con.ConnectionString = connString;                //Pass connection string to SqlConnection class object.
            con.Open();             //Open connection.
            string query = "select * from product";     //create a query variable.
            SqlCommand cmd = new SqlCommand(query, con);    //Create a sqlcommand object and pass query and connection object as parameter. First parameter should be query and second parameter is connection object.
            //Execute query by calling ExecuteReader method.
            cmd.ExecuteReader();   //It will return a DataReader object which contains query result. Here we does not store it.
            Console.WriteLine("Command executed successfully.");
            con.Close();            //Close SqlConnection object.
        }

Example which represents use of Asynchronous programing in ado.net

/// <summary>
        /// This method will display example of asynchronous execution which
        /// will perform by calling method BeginExecuteNonQuery(), BeginExecuteReader(), EndExecuteQuery()
        /// EndExecuteReader() etc. When we call BeginExecuteReader() method then it will return IAsyncResult object
        /// which will be passed to EndExecuteReader() method when we want output of query.
        /// Additional key word which is added in connection string is Asynchronous Processing=true; which tell us
        /// that this command will be executed as asynchronously.
        /// </summary>
        public void asynchronousExample()
        {
            SqlConnection con = new SqlConnection();      //Create an SqlConnection object.
            string connString = "Data Source= AA-PC;User Id=sa;Password=bbbb;Initial Catalog=Workbook;Asynchronous Processing=true;";
            con.ConnectionString = connString;
            con.Open();    //Open SqlConnaction object by calling Open() method of SqlConnection class.
            string query = "select * from product";     //create a query variable.
            SqlCommand cmd = new SqlCommand(query, con);    //Create a sqlcommand object and pass query and connection object as parameter. First parameter should be query and second parameter is connection object.
            IAsyncResult result = cmd.BeginExecuteReader(CommandBehavior.SequentialAccess);       //Call BeginExecuteReader() method which will start Asynchronous execution.
            Console.WriteLine("Asynchronous execution is started.");
            SqlDataReader dr = cmd.EndExecuteReader(result);                    //Call end execute reader method which will display that execution has finished.
            //Display record form datareader object and close connection from server.
            con.Close();            
        }

Thanks.