C# memory shared between two Processes, can't get Read stream from one side

Question

I did exercise with a problem of OS book. I have a difficulty with implementing shared memory between two processes. work procedure is following.

one process(A) starts another process(B). and that one, another process(B), do its job - called collatz conjecture (it is just a iterative work.). To share B's job, B has to write his work into stream.

below is my source code(A).

namespace collatz_conjecture
{
    class colltz_conjecture
    {
        static void Main(string[] args)
        {
            Console.WriteLine("===== Start Process =====");
            MemoryMappedFile mmf = MemoryMappedFile.CreateNew("test", (long)1e5 );

            Process child = new Process();
            child.StartInfo.FileName = "child.exe";
            child.Start();
            child.WaitForExit();

            using (MemoryMappedViewStream stream = mmf.CreateViewStream(0, (long)1e5))
            {
                StreamReader sr = new StreamReader(stream);
                Console.WriteLine(sr.ReadLine());

                Console.WriteLine("===== End of Process =====");
            }
        }
    }
}

and the below is source coude B.

namespace child
{
    class child
    {
        static void Main(string[] args)
        {
            Console.WriteLine("임의의 정수를 입력해주세요");
            int n =Convert.ToInt32(Console.ReadLine());
            try
            {
                using (MemoryMappedFile mmf = MemoryMappedFile.OpenExisting("test",MemoryMappedFileRights.Write))
                {
                    using (MemoryMappedViewStream stream = mmf.CreateViewStream(0, (long)1e2))
                    {
                        StreamWriter sw = new StreamWriter(stream);

                        while (true)
                        {
                            sw.Write(n + " " );
                            Console.Write(n + " ");
                            if (n == 1) break;

                            if (n % 2 == 0) n /= 2;
                            else n = 3 * n + 1;
                            Thread.Sleep(500);
                        }
                        Console.WriteLine();
                    }
                }
            }
            catch
            {
                while (true)
                {
                    Console.Write("WHY IT DOESNT WORK????\n");
                    Thread.Sleep(500);
                };
            }
         }
    }
}

I think I did what i can do at that time. I copied msdn's source msdn's example, and pasted into my source. It worked correctly.

but with my source, A just print out null string..

is It banned use streamReader in MemoryMappedFile? or what is the problem

picture of two console, left one is A right one is B.

Answer 1

Solved. The matter is about the.... "StreamWriter". I'm really sorry that It is not the IPC one. I figured out that StreamWriter should follow Close or flush. So I added "sw.Flush()"

static void Main(string[] args)
    {
        Console.WriteLine("임의의 정수를 입력해주세요");
        int n =Convert.ToInt32(Console.ReadLine());
        try
        {
            using (MemoryMappedFile mmf = MemoryMappedFile.OpenExisting("test",MemoryMappedFileRights.Write))
            {
                using (MemoryMappedViewStream stream = mmf.CreateViewStream(0, (long)1e2))
                {
                    StreamWriter sw = new StreamWriter(stream);

                    while (true)
                    {
                        sw.Write(n + " " );
                        Console.Write(n + " ");
                        if (n == 1) break;

                        if (n % 2 == 0) n /= 2;
                        else n = 3 * n + 1;
                        Thread.Sleep(500);
                    }
                    sw.Flush();  // <---- added
                    Console.WriteLine();
                }
            }
        }
        catch
        {
            while (true)
            {
                Console.Write("WHY IT DOESNT WORK????\n");
                Thread.Sleep(500);
            };
        }
     }

and It works well..

sorry. I think my ask was not good enough to post. but I hope my ask, answer will help someone.