Two-way operation between two processes using named pipes in C #

I am trying to use named pipes for communication between a server and a client process on the same machine. the server sends a message to the client, the client does something with it and returns the result, and the server should get the result.

here is the code for the server:

using System;
using System.IO;
using System.IO.Pipes;

class PipeServer
{
    static void Main()
    {
        using (NamedPipeServerStream pipeServer =
            new NamedPipeServerStream("testpipe", PipeDirection.InOut))
        {
            Console.WriteLine("NamedPipeServerStream object created.");

            // Wait for a client to connect
            Console.Write("Waiting for client connection...");
            pipeServer.WaitForConnection();

            Console.WriteLine("Client connected.");
            try
            {
                // Read user input and send that to the client process.
                using (StreamWriter sw = new StreamWriter(pipeServer))
                {
                    sw.AutoFlush = true;
                    Console.Write("Enter text: ");
                    sw.WriteLine(Console.ReadLine());
                }

                pipeServer.WaitForPipeDrain();

                using (StreamReader sr = new StreamReader(pipeServer))
                {
                    // Display the read text to the console 
                    string temp;

                    // Wait for result from the client. 
                    while ((temp = sr.ReadLine()) != null)
                    {
                        Console.WriteLine("[CLIENT] Echo: " + temp);
                    }
                }

            }
            // Catch the IOException that is raised if the pipe is 
            // broken or disconnected.
            catch (IOException e)
            {
                Console.WriteLine("ERROR: {0}", e.Message);
            }
        }
    }
}

and here is the code for the client:

using System;
using System.IO;
using System.IO.Pipes;

class PipeClient
{
    static void Main(string[] args)
    {
        using (NamedPipeClientStream pipeClient =
            new NamedPipeClientStream(".", "testpipe", PipeDirection.InOut))
        {

            // Connect to the pipe or wait until the pipe is available.
            Console.Write("Attempting to connect to pipe...");
            pipeClient.Connect();

            Console.WriteLine("Connected to pipe.");
            Console.WriteLine("There are currently {0} pipe server instances open.",
               pipeClient.NumberOfServerInstances);
            using (StreamReader sr = new StreamReader(pipeClient))
            {
                // Display the read text to the console
                string temp;
                while ((temp = sr.ReadLine()) != null)
                {
                    Console.WriteLine("Received from server: {0}", temp);
                }
            }


            // send the "result" back to the Parent process.
            using (StreamWriter sw = new StreamWriter(pipeClient))
            {
                sw.AutoFlush = true;
                sw.WriteLine("Result");
            }

            pipeClient.WaitForPipeDrain();

        }
        Console.Write("Press Enter to continue...");
        Console.ReadLine();
    }
}

But in the server code, on the line pipeServer.WaitForPipeDrain (); I get an ObjectDisposedException, and it says, "Cannot access the private channel."

I also get the same error in client code when setting sw.AutoFlush to true.

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Advance.