在从 NetworkStream 读取之前，我的程序冻结

Question

Hello I am a student and I'm not used to c# yet. I am writing a program with server and client, which are connected with socket. I am trying to implement a way to read from stream, when data is available, with while loop. I can avoid chrashing if I show message with MessageBox.Show() before reading/writing stream. I don't know why program without displayed message isn't working...

public partial class Form1 : Form
{
    const int port = 22222;
    const string ip = "127.0.0.1";
    IPAddress ipServer = IPAddress.Parse(ip);
    TcpListener server = null;
    TcpClient client = null;
    Thread thServer = null;
    Thread thClient = null;
    NetworkStream dataStream = null;
    const int a = 11;
    const int n = 251;
    string receivedMessage = "";
    bool? izbira = null;



    public Form1()
    {
        InitializeComponent();

        thServer = new Thread(new ThreadStart(startServer));
        thServer.IsBackground = true;
        thServer.Start();    
    }

    void startServer() {

        server = new TcpListener(ipServer, port);
        server.Start();
        textBox4.Invoke(new Action(() => textBox4.AppendText("Strežnik: zagnan na: IP: " + ip + ", port:" + port)));
        client = new TcpClient();
        client = server.AcceptTcpClient();
        NetworkStream dataStream = client.GetStream();
        textBox4.Invoke(new Action(() => textBox4.AppendText(Environment.NewLine + "Strežnik: Sprejet nov uporabnik")));
        if (izbira == true)
        {
            byte[] message = new byte[1024];
            if(dataStream.DataAvailable)
                dataStream.Read(message, 0, message.Length);
            receivedMessage = Encoding.UTF8.GetString(message);
            textBox4.Invoke(new Action(() => textBox4.AppendText(Environment.NewLine + "Strežnik: Dobil sem sporočilo: " + receivedMessage)));

            message = new byte[1024];
            message = Encoding.UTF8.GetBytes("drugo sporocilo!");
            dataStream.Write(message, 0, message.Length);
        }
        else {
            byte[] message = new byte[1024];
            message = Encoding.UTF8.GetBytes("serbus");
            dataStream.Write(message, 0, message.Length);


        }

    }

    void button1_Click(object sender, EventArgs e) {
        if (izbira == null) {
            textBox4.Invoke(new Action(() => textBox4.AppendText(Environment.NewLine + "Izbrati morate ali boste datoteko prenesli ali poslali!")));
            return;
        }
        this.button1.Enabled = false;
        client = new TcpClient();
        IPAddress insertedIp = IPAddress.Parse(textBox1.Text);

        client.Connect(insertedIp, Convert.ToInt32(textBox3.Text));
        dataStream = client.GetStream();


        if (izbira == true)
        {
            byte[] message = new byte[1024];
            message = Encoding.UTF8.GetBytes("hejj");

            dataStream.Write(message, 0, message.Length);

            message = new byte[1024];

            MessageBox.Show("");
            while (true)
            {
                if (dataStream.DataAvailable)
                {

                    dataStream.Read(message, 0, message.Length);
                    break;
                }
            }

            receivedMessage = Encoding.UTF8.GetString(message);
            textBox4.Invoke(new Action(() => textBox4.AppendText(Environment.NewLine + "Strežnik: Dobil sem sporočilo: " + receivedMessage)));
        }
        else {

            byte[] message = new byte[1024];
            MessageBox.Show("Serbus");
            while (true)
            {
                if (dataStream.DataAvailable)
                {

                    dataStream.Read(message, 0, message.Length);
                  break;
                }

            }
            receivedMessage = Encoding.UTF8.GetString(message);
            textBox4.Invoke(new Action(() => textBox4.AppendText(Environment.NewLine + "Strežnik: Dobil sem sporočilo: " + receivedMessage)));
        }
    }

    void buttonUpload_Click(object sender, EventArgs e) {
        izbira = true;
        this.buttonDownload.Enabled = false;
    }
    void buttonDownload_Click(object sender, EventArgs e) {
        izbira = false;
        this.buttonUpload.Enabled = false;
        this.button2.Text = "Prenesi";
    }

Answer 1

Now this is mostly guessing, as we barely have enough code to say anything for certain:

What about the JiT Compiler?

One of it's purposes is dead code detection. It cuts out code it predicts will not have an effect. Unfortunately, it is still only a computer programm, so false positives happen. For example, trying to force a OOM Exception for x32 Framework installations, I had to go out of my way to not have the code cut out by the JiT:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace OOM_32_forced
{
    class Program
    {
        static void Main(string[] args)
        {
            //each short is 2 byte big, Int32.MaxValue is 2^31.
            //So this will require a bit above 2^32 byte, or 2 GiB
            short[] Array = new short[Int32.MaxValue];

            /*need to actually access that array
            Otherwise JIT compiler and optimisations will just skip
            the array definition and creation */
            foreach (short value in Array)
                Console.WriteLine(value);
        }
    }
}

A MessageBox will prevent this whole function from being cut out as dead code. Outputting something towards the user is alwasy asumed to "have a effect". However seperate parts of it are still eligible for dead code detection.

Unforunately you have not provided us with a minimal, complete verifyable example. So we can not really help you figure it out any further.