Stream Console process output to Textbox In real - Time

Question

I'm pretty much very new at C# and windows forms programming. I'm trying to build a very very simple form. I have only one button and a text box , When i click the button a process start at the background ( it's a process that i programmed in Python and compile to EXE file) , it's very simple process ... just print number from 1 to 4 in a 2 sec delay between each number I want the output to be display at the text box in a real-time meaning the number 1 to 4 in a 2 sec delay. I looked online and search a lot but couldn't find anything to help me with that. i read this thread -->How can I redirect process output (console) to richtextbox? and tried to implement what written there with no luck Thanks a lot! This is my code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;

    namespace WindowsFormsApplication1
    {
        public partial class Form1 : Form
        {
            private StringBuilder sortOutput;
            public Form1()
            {
                InitializeComponent();
            }

            private void button1_Click(object sender, EventArgs e)
            {
                String output="";

                using (Process sortProcess = new Process())
                {
                    sortProcess.StartInfo.FileName = @"c:/req/dist/ex/ex.exe";
                    sortProcess.StartInfo.CreateNoWindow = true;
                    sortProcess.StartInfo.UseShellExecute = false;
                    sortProcess.StartInfo.RedirectStandardOutput = true;
                    sortProcess.Start();
                    output = sortProcess.StandardOutput.ReadLine();
                    //  sortProcess.WaitForExit();
                    while (!(sortProcess.HasExited))
                    {
                        richTextBox1.AppendText(output.ToString());
                          Application.DoEvents(); // This keeps your form responsive by processing events
                    }

                }
                //richTextBox1.AppendText(sortOutput.ToString());
            }
            private void richTextBox1_TextChanged(object sender, EventArgs e)
            {
                //?????
            }
        }
    }

where does your python exe prints the number when it's run directly. Do you get the output from python exe when it is executed from command prompt? — amit dayama, Sep 18 '15 at 11:11
Why you removed `sortProcess.OutputDataReceived +=...` and `sortProcess.BeginOutputReadLine();` from the example code? It's essential for the solution. — Ivan Stoev, Sep 18 '15 at 11:19
@amit dayama : i compile the python code to exe file when i run it in the console (cmd) it's print 1...2...3..4 with 2 sec delay between each number — Moshe Abutbul, Sep 18 '15 at 14:33
@Ivan Stoev i don't really know c# but the code in the thread i mention not working for sure so i tried to play with it a bit .. with no luck — Moshe Abutbul, Sep 18 '15 at 14:35
@ivan Stoev I'm getting this Error: code: Error 1 'WindowsFormsApplication1.Form1' does not contain a definition for 'richTextBox1_TextChanged' and no extension method 'richTextBox1_TextChanged' accepting a first argument of type 'WindowsFormsApplication1.Form1' could be found (are you missing a using directive or an assembly reference?) C:\Users\Itamar\Documents\Visual Studio 2010\Projects\WindowsFormsApplication1\WindowsFormsApplication1\Form1.Designer.cs 54 75 WindowsFormsApplication1 — Moshe Abutbul, Sep 18 '15 at 14:42
@Ivan Stoev : Forget the error .. i solve it .. but your code isn't working .. it's printing all the output after the process ended ... meaning it's printing the whole 4 numbers in one time — Moshe Abutbul, Sep 18 '15 at 14:45
Well, I've made a Console app exe which does what you are explaining and the code below works. Something else is wrong at your side. You better provide your python exe then. — Ivan Stoev, Sep 18 '15 at 15:25
@Ivan Stoev python code: import time for i in range (1,5): print i time.sleep(2) — Moshe Abutbul, Sep 18 '15 at 15:40
Sorry, but I have no idea how to create python exes - I'm a C#-er. If you want help, provide the exe. — Ivan Stoev, Sep 18 '15 at 15:59

Ivan Stoev · Answer 1 · 2015-09-19T17:19:50.737

Process.BeginOutputReadLine method in combination with Process.OutputDataReceived event provide asynchronous behavior which fits perfectly in the UI component architecture. You don't need to to call a blocking WaitForExit nor weird while loop with Application.DoEevents as in the referenced thread. All you need is to attach an event handler, call BeginOutputReadLine and handle the received data inside the event. The only tricky (but at the same time standard for UI code) part is to make sure UI is updated only from the UI thread and do a little thread synchronization. Something like this:

using System;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private object syncGate = new object();
        private Process process;
        private StringBuilder output = new StringBuilder();
        private bool outputChanged;

        private void button1_Click(object sender, EventArgs e)
        {
            lock (syncGate)
            {
                if (process != null) return;
            }

            output.Clear();
            outputChanged = false;
            richTextBox1.Text = "";

            process = new Process();
            process.StartInfo.FileName = @"c:/req/dist/ex/ex.exe";
            process.StartInfo.CreateNoWindow = true;
            process.StartInfo.UseShellExecute = false;
            process.StartInfo.RedirectStandardOutput = true;
            process.OutputDataReceived += OnOutputDataReceived;
            process.Exited += OnProcessExited;
            process.Start();
            process.BeginOutputReadLine();
        }

        private void OnOutputDataReceived(object sender, DataReceivedEventArgs e)
        {
            lock (syncGate)
            {
                if (sender != process) return;
                output.AppendLine(e.Data);
                if (outputChanged) return;
                outputChanged = true;
                BeginInvoke(new Action(OnOutputChanged));
            }
        }

        private void OnOutputChanged()
        {
            lock (syncGate)
            {
                richTextBox1.Text = output.ToString();
                outputChanged = false;
            }
        }

        private void OnProcessExited(object sender, EventArgs e)
        {
            lock (syncGate)
            {
                if (sender != process) return;
                process.Dispose();
                process = null;
            }
        }
    }
}

EDIT The above method works only for lines and looks like your python exe is outputting characters. Here is a modified version that should work in that scenario:

using System;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
using System.Threading;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private object syncGate = new object();
        private Process process;
        private StringBuilder output = new StringBuilder();
        private bool outputChanged;

        private void button1_Click(object sender, EventArgs e)
        {
            lock (syncGate)
            {
                if (process != null) return;
            }

            output.Clear();
            outputChanged = false;
            richTextBox1.Text = "";

            process = new Process();
            process.StartInfo.FileName = @"c:/req/dist/ex/ex.exe";
            process.StartInfo.CreateNoWindow = true;
            process.StartInfo.UseShellExecute = false;
            process.StartInfo.RedirectStandardOutput = true;
            process.Start();

            new Thread(ReadData) { IsBackground = true }.Start();
        }


        private void ReadData()
        {
            var input = process.StandardOutput;
            int nextChar;
            while ((nextChar = input.Read()) >= 0)
            {
                lock (syncGate)
                {
                    output.Append((char)nextChar);
                    if (!outputChanged)
                    {
                        outputChanged = true;
                        BeginInvoke(new Action(OnOutputChanged));
                    }
                }
            }
            lock (syncGate)
            {
                process.Dispose();
                process = null;
            }
        }

        private void OnOutputChanged()
        {
            lock (syncGate)
            {
                richTextBox1.Text = output.ToString();
                outputChanged = false;
            }
        }
    }
}

... Sorry but it's not working .. still the same problem .. all the out put is printed after the process ended and not in real-time — Moshe Abutbul, Sep 18 '15 at 14:48
No man still no working ... my python code is very very simply , just print number in a 2 sec delay i compile it to EXE file using pyinstaller ... i can run it from CMD by just typing the name of the program .. your code is print the output after 8 sec when the process ends and NOT while it's running... can i send u somehow the EXE file? Thanks — Moshe Abutbul, Sep 18 '15 at 19:08
No, sorry - I'm taking off. Obviously there is a problem in your python exe. Before posting any of my two answers I've made a simple C# Console exe apps that do what you are explaining, and both code snippets work. Good luck. — Ivan Stoev, Sep 18 '15 at 19:16
Sorry for that. but i think the mistake is on your side.. i made a very simple Python code and compile to EXE ... Your code print the program output after the process is done. Thanks anyway .. i hope someone will help me with that very very simply problem — Moshe Abutbul, Sep 20 '15 at 01:35

score 0 · Answer 2 · answered Nov 11 '20 at 21:27

0

I've found the problem mentionned in the response of Ivan Stoev. The textbox only update after process ended.

In fact, the code work pretty well with a batch file. But i faced the same issue with python code. The problem is in fact in the python code. After printing, you have to flush fflush(stdout).

So in my python code, i just had to add :

print("Something", flush=True)

And now it's work!

answered Nov 11 '20 at 21:27

Maxime

43
6

1

Running python with the -u option (unbuffered) tends to be the easier solution. – Hans Passant Nov 11 '20 at 22:40

Stream Console process output to Textbox In real - Time

2 Answers2