WndProc not called in hosted process in wpf

Question

Following the instructions in:

How to run an application inside wpf application?

and in the walkthrough in MSDN (https://msdn.microsoft.com/en-us/library/ms752055.aspx)

I have managed to host my console applications in wpf. (Note: there are more than 2 applications to be hosted)

In ControlHost.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Threading;
using System.Runtime.InteropServices;
using System.Windows.Interop;

namespace Try
{
public class ControlHost : HwndHost
{
    private static List<Process> _procList = new List<Process>();
    IntPtr hwndControl;
    int hostHeight, hostWidth;
    string filePath;

    internal const int
    WS_CHILD = 0x40000000,
    GWL_STYLE = -16,
    WS_CAPTION = 0x00C00000,
    WS_THICKFRAME = 0x00040000;

    [DllImport("user32.dll")]
    private static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern int GetWindowLong(IntPtr hWnd, int nIndex);

    [DllImport("user32")]
    private static extern IntPtr SetParent(IntPtr hWnd, IntPtr hWndParent);

    [DllImport("user32.dll", EntryPoint = "DestroyWindow", CharSet = CharSet.Unicode)]
    internal static extern bool DestroyWindow(IntPtr hwnd);

    public ControlHost(double height, double width, string filePathName)
    {
          hostHeight = (int)height;
          hostWidth = (int)width;
          filePath = filePathName;
    }

    protected override HandleRef BuildWindowCore(HandleRef hwndParent)
    {
        Process _process = new Process();
        _process.StartInfo.FileName = filePath;
        _process.StartInfo.WindowStyle = ProcessWindowStyle.Minimized;
        _process.Start();
        _procList.Add(_process);

        // The main window handle may be unavailable for a while, just wait for it
        while (_process.MainWindowHandle == IntPtr.Zero)
        {
            Thread.Yield();
        }

        hwndControl = _process.MainWindowHandle;

        int style = GetWindowLong(hwndControl, GWL_STYLE);
        style = style & ~((int)WS_CAPTION) & ~((int)WS_THICKFRAME); // Removes Caption bar and the sizing border
        style |= ((int)WS_CHILD); // Must be a child window to be hosted

        SetWindowLong(hwndControl, GWL_STYLE, style);
        SetParent(hwndControl, hwndParent.Handle);

        this.InvalidateVisual();

        HandleRef hwnd = new HandleRef(this, hwndControl);
        return hwnd;
    }

    protected override IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        handled = false;
        return IntPtr.Zero;
    }

    protected override void DestroyWindowCore(HandleRef hwnd)
    {
        DestroyWindow(hwnd.Handle);
        if (_procList != null)
        {
            foreach (Process p in _procList)
            {
                if (p != null)
                {
                    try
                    {
                        while (!p.HasExited)
                        {
                            p.Refresh();
                            p.CloseMainWindow();
                            p.Kill();
                            Thread.Sleep(10);
                        }
                    }
                    catch
                    {

                    }
                }
            }
        }
    }

    public void Stop(IntPtr Hwnd)
    {
        HandleRef hwnd = new HandleRef(this, Hwnd);

        DestroyWindow(hwnd.Handle);
        if (_procList != null)
        {
            foreach (Process p in _procList)
            {
                if (p != null)
                {
                    try
                    {
                        while (!p.HasExited)
                        {
                            p.Refresh();
                            p.CloseMainWindow();
                            p.Kill();
                            Thread.Sleep(10);
                        }
                    }
                    catch
                    {

                    }
                }
            }
        }
    }
}
}

and in MainWindow.xaml.cs:

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;
    using System.Windows;
    using System.Windows.Controls;
    using System.Windows.Data;
    using System.Windows.Documents;
    using System.Windows.Input;
    using System.Windows.Media;
    using System.Windows.Media.Imaging;
    using System.Windows.Navigation;
   using System.Windows.Shapes;
    using Microsoft.Win32;

namespace Try
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private string[] appsList;
        private List<ControlHost> ctrlHostList = new List<ControlHost>();
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            ControlHost appsControl;
            Border appsBorder;
            foreach (string app in appsList)
            {
                appsBorder = new Border();
                appsBorder.Height = double.NaN;
                appsBorder.Width = double.NaN;
                appsBorder.BorderBrush = Brushes.Silver;
                appsBorder.BorderThickness = new Thickness(1);
                appsControl = new ControlHost(appsBorder.ActualHeight, appsBorder.ActualWidth, app);
                ctrlHostList.Add(appsControl);
                appsBorder.Child = appsControl;
                WP_Apps.Children.Add(appsBorder);
            }
        }

        private void Button_Click_1(object sender, RoutedEventArgs e)
        {
            OpenFileDialog _openFileDlg = new OpenFileDialog();
            _openFileDlg.Multiselect = true;

            if (_openFileDlg.ShowDialog() == true)
            {
                appsList = _openFileDlg.FileNames;
            }
        }

        private void Button_Click_2(object sender, RoutedEventArgs e)
        {
            foreach(ControlHost CH in ctrlHostList)
            {
                CH.Stop(CH.Handle);
            }
        }
    }
}

and finally in MainWindow.xaml:

<Window x:Class="Try.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="1502" Width="1500" ResizeMode="CanMinimize" WindowStartupLocation="CenterScreen" WindowState="Maximized" >
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="76*"/>
            <ColumnDefinition Width="671*"/>
        </Grid.ColumnDefinitions>
        <Button Content="Start" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top" Width="75" Height="20" Click="Button_Click"/>
        <Button Content="GetApps" HorizontalAlignment="Left" Height="21" Margin="10,54,0,0" VerticalAlignment="Top" Width="74" Click="Button_Click_1"/>
        <ScrollViewer Grid.Column="1">
            <WrapPanel Name="WP_Apps" Grid.Column="1" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Width="Auto" />
        </ScrollViewer>
        <Button Content="Stop" HorizontalAlignment="Left" Margin="10,99,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click_2"/>

    </Grid>
</Window>

First, I will get the apps by clicking the "Get Apps" buttons than click "Start" The result will look like this:

But only one hosted application accept user inputs. (In this example, its the 1st application, circled in red who have can have user inputs) The other 2 does not accept any user input. Nothing is triggered when clicking on the other 2 applications.

I know I have not handled a lot of situations. But that did not influence the problem that I am having at the moment, i presumed. This is a simple application (not the real application) that i wrote, which i hope that someone will be able to reproduce the same error that I have.

Is there anything that I'm doing wrong? Or have I missed something? Any suggestions would be greatly appreciated. Thanks in advance!

Answer 1

I found a workaround for this problem,

that is to use WindowsFormsHost to host the console application as in this example.

I created a System.Windows.Forms.Panel and set it as a Child of the WindowsFormsHost and once again add it into the children of a Wrap Panel.

Somehow, all the hosted applications are able to receive user inputs.

As to why, using HwndHost and Border to host console applications, do not receive user inputs, I still do not know why.

But I think its because:

1. I set the hosted application's window style to Child which makes it unable to receive user inputs. (I know I have read it somewhere, but forgot where)
2. WndProc only receives Form messages, it does not have access to/catch the messages going in consoles.

These are the 2 reasons that I can think of that are causing the hosted applications not being able to receive user inputs.

Correct me if I'm wrong.

Best Regards,
Kai