I have windows forms app. When it's closed the main window is disposed and then when user click on tray window is recreated - it works. However I have werid problem when I try to bring application back when using FileSystemWatcher. Idea is simple, when file is changed application is brought back. However in this case application appears but hangs and then dissapears. The shape of window comes back but is unresponsive, moving mouse on window shows like app is "thinking" or "hanging", the app doesn't have icon on taskbar.
My guess is that this is connected with threads/synchronization but I have no idea how to make it work again. I tried many different things connected with threading but failed. I cannot create this window again in UI thread because as I understand I can write _mainWindow.BeginInvoke but I can't do that before I create this form.
I have created the minimal working example that demonstrates the issue. It is available at https://gitlab.com/virtual92/getting-forms-up or here:
Program.cs
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace GettingFormsUp
{
static class Program
{
private static bool hideFlag = true;
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
var initApplicationContext = new InitApplicationContext();
Console.WriteLine();
var fileSystemWatcher = new FileSystemWatcher(Path.GetFullPath("../.."), "watcher");
fileSystemWatcher.Changed += (sender, args) =>
{
Console.WriteLine("Watched");
initApplicationContext.Show();
};
fileSystemWatcher.EnableRaisingEvents = true;
Application.Run(initApplicationContext);
}
private class InitApplicationContext : ApplicationContext
{
private static MainWindow _mainWindow;
public InitApplicationContext()
{
NewForm();
}
private void NewForm()
{
Console.WriteLine("Creating new MainWindow");
_mainWindow = new MainWindow();
_mainWindow.Invoke((MethodInvoker) delegate
{
_mainWindow.Show();
});
}
public void Show()
{
if (_mainWindow == null || _mainWindow.IsDisposed)
{
NewForm();
}
else if (!_mainWindow.Visible)
{
_mainWindow.BeginInvoke((MethodInvoker) delegate
{
Console.WriteLine("showing");
_mainWindow.Show();
});
}
}
public void Delete()
{
if (_mainWindow != null && !_mainWindow.IsDisposed)
{
_mainWindow.Dispose();
}
}
}
}
}
MainWindow.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace GettingFormsUp
{
public class MainWindow : Form
{
public MainWindow()
{
CreateHandle();
InitializeComponent();
}
private System.ComponentModel.IContainer components = null;
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
}
private void InitializeComponent()
{
this.components = new System.ComponentModel.Container();
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.Text = "Form1";
}
}
}
How can I make it work?
The problem with your code is that when you create the window again, it's being created in the thread used to raise the FileSystemWatcher.Changed event, which is a background thread, not the thread that the Application.Run() method is using to pump window messages. So that background thread winds up owning the window.
Messages for the window are sent to the thread that owns it, but that thread doesn't have a message pumping loop, so the window never sees the messages. Those messages are critical, as they are what handle everything about the interaction with the window, both user input and everything involved in drawing the window (except for the bare minimum, which the Windows desktop manager handles). Those messages are even used to handle things like calls to Control.Invoke() and Control.BeginInvoke(). Without the message-pumping loop, BeginInvoke() delegates will never be handled, and Invoke() will never even return.
There are a variety of ways to address this. Simply not disposing the window in the first place could be an option (you can override OnFormClosing(), canceling the event and hiding the window instead). Then the call to _mainWindow.Invoke() will always go to the correct thread and work like you expect:
public partial class MainWindow : Form
{
// ...
protected override void OnFormClosing(FormClosingEventArgs e)
{
Visible = false;
e.Cancel = true;
base.OnFormClosing(e);
}
// ...
}
Alternatively, you can capture the main thread's SynchronizationContext object, which can be used to do the same thing as Control.Invoke()/BeginInvoke(). The key to that technique is that until you've created a Winforms component in a thread, that thread won't have a SynchronizationContext. In your code, the form is created when you create the InitApplicationContext object, so capturing the SynchronizationContext after that will work:
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
var initApplicationContext = new InitApplicationContext();
SynchronizationContext context = SynchronizationContext.Current;
Console.WriteLine();
string path = Path.GetFullPath("../..");
Console.WriteLine($"Watching {path}");
var fileSystemWatcher = new FileSystemWatcher(path, "watcher");
fileSystemWatcher.Changed += (sender, args) =>
{
context.Post(o =>
{
Console.WriteLine("Watched");
initApplicationContext.Show();
}, null);
};
fileSystemWatcher.EnableRaisingEvents = true;
Application.Run(initApplicationContext);
}
If you take this approach, then of course you don't need the call to Control.Invoke() when creating the window. It's superfluous the first time anyway, and because you'll be using SynchronizationContext from the FileSystemWatcher.Changed event handler in the subsequent instances, it's also unneeded then:
private void NewForm()
{
Console.WriteLine("Creating new MainWindow");
_mainWindow = new MainWindow();
_mainWindow.Show();
}
Related
I am creating a new window in a thread in .Net Framework 4.8 WPF application.
Most of time it works. However sometimes it hangs even when the app starts.
The dispatcher in the main thread and the dispatcher in the new thread wait each other.
You can refer to the following window to check threads.
The following is the entire .cs code to reproduce the phenomenon. 'NewWindow' is a class derived from 'System.Windows.Window' and it does not have to have anything in it to reproduce the phenomenon(For clarification I also put code for 'NewWindow' at the end of this question).
using System;
using System.Threading;
using System.Windows;
using System.Windows.Interop;
namespace WindowCreateTest
{
public partial class MainWindow : Window
{
NewWindow newWindow = null;
Thread uiThread = null;
public MainWindow()
{
InitializeComponent();
}
public void ShowNewWindow(IntPtr handle)
{
uiThread = new Thread(() =>
{
Thread.CurrentThread.Name = "ShowNewWindow Thread";
if (newWindow == null)
newWindow = new NewWindow();
WindowInteropHelper helper = new WindowInteropHelper(newWindow);
helper.Owner = handle;
newWindow.Show();
System.Windows.Threading.Dispatcher.Run();
});
uiThread.SetApartmentState(ApartmentState.STA);
uiThread.Start();
}
private void Window_Loaded(object sender, RoutedEventArgs e)
{
var h = new WindowInteropHelper(this).Handle;
ShowNewWindow(h);
}
}
}
You might wonder why I'm creating a new window in a newly created thread not in a main thread. The reason is that, this code is used in MAF(Managed Add-ins and Extensibility Framework or System.AddIn) dlls which is activated in an external process.
WindowInteropHelper helper = new WindowInteropHelper(newWindow);
helper.Owner = handle;
The reason I put the above two lines is
to make 'NewWindow' minimized when I minimize 'MainWindow'
to make 'NewWindow' always be placed over 'MainWindow'.
And I guess this is the root cause of the deadlock.
using System.Windows;
namespace WindowCreateTest
{
public partial class NewWindow : Window
{
public NewWindow()
{
InitializeComponent();
}
}
}
Thank you for reading and any advice will be welcomed and appreciated.
I've got a WinForm app that parents Windows of other processes (ex. Google Chrome). I'm using the following code to parent a Windows to my Form, using the Handle returned by [Process].MainWindowHandle.
I'm trying to find the MainWindowTitle of all the Windows that are parented to my Form, so I can display their name on a Label.
When the Window of a WebBrowser is embedded, the Title will change when a different Web Page is selected, switching Tabs.
The code I have for starting the program does work as it should:
ProcessStartInfo ps1 = new ProcessStartInfo(#"C:/Users/Jacob/AppData/Roaming/Spotify/Spotify.exe");
ps1.WindowStyle = ProcessWindowStyle.Minimized;
Process p1 = Process.Start(ps1);
// Allow the process to open it's window
Thread.Sleep(1000);
appWin1 = p1.MainWindowHandle;
spotify = p1;
// Put it into this form
SetParent(appWin1, this.Handle);
// Move the window to overlay it on this window
MoveWindow(appWin1, 0, 70, this.Width / 2, this.Height/2, true);
Since you're willing to use UIAutomation to handle this parenting affair, I propose to handle this using Automation methods entirely. Almost, SetParent still required :).
The class shown here uses the WindowPatter.WindowOpenedEvent to detect and notify when a new Window is opened in the System.
It can be any Window, Console included (still a Window).
This method allows to identify a Window when it's handle is already created, so you don't need an arbitrary time-out or try to use Process.WaitForInputIdle(), which may not have the desired result.
You can pass a list of names of processes to the ProcessNames Property of the class: when any Window that belongs to one of these Processes is opened, UIAutomation detects it and a public event is raised. It notifies the subscribers that one of the Processes in the list has opened a Window, which is the ProcessId of the Owner and the handle of the Windows.
These values are passed in a custom EventArgs class, ProcessStartedArgs when the ProcessStarted event is raised.
Since the Automation Event is raised in a Thread other than the UI Thread, the class captures the SynchronizationContext where the class is created (the UI Thread, since you're probably creating this class in a Form) and marshals the event to that Thread, calling its Post() method passing a SendOrPostCallback delegate.
This way, you can safely pass the Handle of your Form and the Handle of the Window to SetParent().
To retrieve the current Title (Caption) of the parented Window, pass the Handle previously returned in the event argument to the GetCurrentWindowTitle() method. If the Window contains tabbed child Windows, as a Web Browser, this method will return the Title related to the Tab currently selected.
▶ The class is disposable and you need to call its public Dispose() method. This removes the Automation event handler and also all the events in the Invocation List of the public event you have subscribed to. This way, you can use a Lambda to subscribe to the event.
Use a Field to store an instance of this class. Create the instance when needed, passing a List of Process Names you're interested in.
Subscribe to the ProcessStarted event.
When on of these Processes opens a new Window, you'll get a notification and the parenting thing can be performed:
public partial class SomeForm : Form
{
private WindowWatcher watcher = null;
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
watcher = new WindowWatcher();
watcher.ProcessNames.AddRange(new[] { "msedge", "firefox", "chrome", "notepad" });
watcher.ProcessStarted += (o, ev) => {
SetParent(ev.WindowHandle, this.Handle);
MoveWindow(ev.WindowHandle, 0, 70, this.Width / 2, this.Height / 2, true);
string windowTitle = WindowWatcher.GetCurrentWindowTitle(ev.WindowHandle);
};
}
protected override void OnFormClosed(FormClosedEventArgs e)
{
watcher.Dispose();
base.OnFormClosed(e);
}
}
WindowWatcher class:
NOTE: UI Automation assemblies are part of Windows Presentation Framework.
When one of these assemblies is referenced in a WinForms application, the WinForms application will become DpiAware (SystemAware), if it's not already DpiAware.
This can have an impact on the Layout of one or more Forms that is not designed to handle Dpi Awareness changes and notifications.
Requires a Project Reference to:
UIAutomationClient
UIAutomationTypes
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Automation;
public class WindowWatcher : IDisposable
{
private SynchronizationContext context = null;
private readonly SendOrPostCallback eventCallback;
public event EventHandler<ProcessStartedArgs> ProcessStarted;
private AutomationElement uiaWindow;
private AutomationEventHandler WindowOpenedHandler;
public WindowWatcher() {
context = SynchronizationContext.Current;
eventCallback = new SendOrPostCallback(EventHandlersInvoker);
InitializeWatcher();
}
public List<string> ProcessNames { get; set; } = new List<string>();
private void InitializeWatcher()
{
Automation.AddAutomationEventHandler(
WindowPattern.WindowOpenedEvent, AutomationElement.RootElement,
TreeScope.Children, WindowOpenedHandler = new AutomationEventHandler(OnWindowOpenedEvent));
}
public static string GetCurrentWindowTitle(IntPtr handle)
{
if (handle == IntPtr.Zero) return string.Empty;
var element = AutomationElement.FromHandle(handle);
if (element != null) {
return element.Current.Name;
}
return string.Empty;
}
private void OnWindowOpenedEvent(object uiaElement, AutomationEventArgs e)
{
uiaWindow = uiaElement as AutomationElement;
if (uiaWindow == null || uiaWindow.Current.ProcessId == Process.GetCurrentProcess().Id) return;
var window = uiaWindow.Current;
var procName = string.Empty;
using (var proc = Process.GetProcessById(window.ProcessId)) {
if (proc == null) throw new InvalidOperationException("Invalid Process");
procName = proc.ProcessName;
}
if (ProcessNames.IndexOf(procName) >= 0) {
var args = new ProcessStartedArgs(procName, window.ProcessId, (IntPtr)window.NativeWindowHandle);
context.Post(eventCallback, args);
}
}
public class ProcessStartedArgs : EventArgs
{
public ProcessStartedArgs(string procName, int procId, IntPtr windowHandle)
{
ProcessName = procName;
ProcessId = procId;
WindowHandle = windowHandle;
}
public string ProcessName { get; }
public int ProcessId { get; }
public IntPtr WindowHandle { get; }
}
private void EventHandlersInvoker(object state)
{
if (!(state is ProcessStartedArgs args)) return;
ProcessStarted?.Invoke(this, args);
}
~WindowWatcher() { Dispose(false); }
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected void Dispose(bool disposing)
{
if (uiaWindow != null && WindowOpenedHandler != null) {
Automation.RemoveAutomationEventHandler(
WindowPattern.WindowOpenedEvent, uiaWindow, WindowOpenedHandler);
}
if (ProcessStarted != null) {
var invList = ProcessStarted.GetInvocationList();
if (invList != null && invList.Length > 0) {
for (int i = invList.Length - 1; i >= 0; i--) {
ProcessStarted -= (EventHandler<ProcessStartedArgs>)invList[i];
}
}
}
}
}
I'm creating a checkout system for a supermarket. It consists of a checkout, server and MIS program an operates WCF services between them. The problem I have is that the checkout program, which is a windows form, does a few neccessaries in it's application_load method and then just quits.
Here's the 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 CheckoutLibrary;
using Checkout.ServerLibraryService;
using Checkout.MarketService;
namespace Checkout
{
public partial class theForm : Form
{
private static int checkoutID = 3;
private Product[] allProducts;
public theForm()
{
InitializeComponent();
}
private void theForm_Load(object sender, EventArgs e)
{
// First cache all products
SupermarketServiceSoapClient marketService = new SupermarketServiceSoapClient();
allProducts = marketService.GetAllProducts();
// Load the service provided by the server
ServiceClient serverService = new ServiceClient();
// Load the event handlers for the bar code scanner
BarcodeScanner scanner = new BarcodeScanner();
scanner.ItemScanned += new BarcodeScanner.ItemScannedHandler(scanner_ItemScanned);
scanner.AllItemsScanned += new BarcodeScanner.AllItemsScannedHandler(scanner_AllItemsScanned);
scanner.Start(checkoutID);
}
void scanner_AllItemsScanned(EventArgs args)
{
throw new NotImplementedException();
}
void scanner_ItemScanned(ScanEventArgs args)
{
itemTextBox.Text = "Scanned " + GetItemName(args.Barcode);
}
private void scanItemButton_Click(object sender, EventArgs e)
{
scanner_ItemScanned(new ScanEventArgs(GetRandBarcode()));
}
// A barcode -> product name look up method
public string GetItemName(int barcode)
{
return allProducts[barcode].Description + " # " + allProducts[barcode].Price;
}
// Method to grab a random barcode for simulation
private int GetRandBarcode()
{
Random rand = new Random();
return rand.Next(0,500);
}
}
}
And program.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
namespace Checkout
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new theForm());
}
}
}
Thanks for any insight.
In WinForms, if your form_load throws an exception, it quits without displaying anything. Annoying, but I'm guessing that's the problem.
You can try a try/catch, or you can hit CTRL+ALT+E and check the Thrown Column for Common Language Runtime Exceptions to see the error.
UPDATE:
Based on comments, here's a sample way to execute something on another thread.
ThreadStart ts = new ThreadStart(() => {
try {
scanner.Start(checkoutID);
} catch {
// Log error
}
});
Thread t = new Thread(ts);
t.Start();
This is what I want to do:
Have a timer with some interval
In the timer callback code, if some condition is met, another thread should be run
I’ve put my code in a class which is instantiated by the main form and the code is executed upon method call (‘StartSync()’, se sample code).
The problem is that the code runs for a couple of seconds but then terminates. I suppose I’m doing something stupid but I really can’t see what it is. Thankful for any help with regards to this.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Diagnostics;
namespace WindowsFormsApplication1
{
class Syncer
{
static bool SYNC_IN_PROGRESS;
public void StartSync()
{
SYNC_IN_PROGRESS = false;
Timer timer = new Timer(timerCallback, null, 0, 1000);
}
public void timerCallback(Object stateInfo)
{
Debug.WriteLine("Sync?");
if (!SYNC_IN_PROGRESS)
{
SYNC_IN_PROGRESS = true;
Thread thSync = new Thread(new ThreadStart(sync));
thSync.Start();
}
}
void sync()
{
Debug.WriteLine("Syncing...");
SYNC_IN_PROGRESS = false;
}
}
}
At a guess, the Timer is only held in a method variable; it sounds to me like the Timer is getting garbage collected and finalized, hence terminated. I suspect you should hold onto that reference in a field to prevent collection.
As an aside - I doubt it is the cause here, but when dealing with threading you should be religiously aware of access to shared state from multiple threads; for example:
using Monitor (aka lock)
appropriate use of volatile
Interlocked when it fits
Your current access to the static bool will probably work OK, but...
Try this cleaner approach
static volatile bool SYNC_IN_PROGRESS;
static thread syncPoll;
public void StartSync()
{
SYNC_IN_PROGRESS = false;
syncPoll = new Thread(sync);
syncPoll.Start();
}
void sync()
{
while (true)
{
Debug.WriteLine("Sync?");
if (SYNC_IN_PROGRESS) Debug.WriteLine("Syncing...");
Thread.Sleep(1000);
}
}
It does the same you try to do with your current code :) but doesn't use a timer
So here is what I did and it seems to work just fine
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
StartSync();
}
static bool SYNC_IN_PROGRESS;
public void StartSync()
{
SYNC_IN_PROGRESS = false;
System.Threading.Timer timer = new System.Threading.Timer(timerCallback, SYNC_IN_PROGRESS, 0, 1000);
}
public void timerCallback(Object stateInfo)
{
Debug.WriteLine("Sync?");
if (!(bool)stateInfo)
{
SYNC_IN_PROGRESS = true;
Thread thSync = new Thread(new ThreadStart(sync));
thSync.Start();
}
}
void sync()
{
Debug.WriteLine("Syncing...");
SYNC_IN_PROGRESS = false;
}
}
I want my C# .NET application to have a form but not be a form.
When I normally startup a windows forms application, it's like the form is the master of everything else that follows:
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
Instead, I'd like to startup my program, which is then able to show a form, but is not a form itself. In other words, I don't want the master controller of the applicatin being the form, I'd like it instead to be a non-visual logical container, which has the capability to show forms, but isn't a form itself.
I'm not sure if I'm posing the question in a clear way, but I'd like to hear thoughts.
You can just use Application.Run() to get a message-loop running. But you'll need to do something to listen for input - perhaps a systray etc.
You could use an ApplicationContext instead. That gets you the necessary message loop that will keep a form alive, once you decide to create one. Make your Program class look similar to this:
static class Program {
[STAThread]
static void Main() {
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
AppContext = new ApplicationContext();
Application.Run(AppContext);
}
public static void Quit() {
AppContext.ExitThread();
}
public static ApplicationContext AppContext;
}
Beware that the app will not close automatically when you close the last window. Calling ExitThread explicitly is required.
It's fairly common to create a separate Bootstrapper component which you could move the display of the main form to:
using System;
using System.Windows.Forms;
namespace Example
{
internal static class Program
{
[STAThread]
private static void Main()
{
new Bootstrapper().Run();
}
}
public class Bootstrapper
{
public void Run()
{
// [Application initialization here]
ShowView();
}
private static void ShowView()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
}
As Mark_Gravell alluded to, Application.Run() blocks until the Form1 closes. You can open your forms on a separate thread, but that thread will be basically consumed by the form. And when you want the exe to exit, you'll have to manually kill each thread. See the following code. (It doesn't create a console window. I got this by creating a default WinForms app and changing the Program class)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using System.Threading;
namespace WindowsFormsApplication1
{
static class Program
{
static List<Thread> threads = new List<Thread>();
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
for (int i = 0; i < 10; i++)
{
StartThread();
System.Threading.Thread.Sleep(500);
}
//kill each thread so the app will exit, otherwise, the app won't close
//until all forms are manually closed...
threads.ForEach(t => t.Abort());
}
static void StartThread()
{
Thread t = new Thread(ShowForm);
threads.Add(t);
t.Start();
}
static void ShowForm()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
}
Create the app as a console app and then call Application.Run as Marc said when you need a form.
You can also create your own ApplicationContext
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(AppController.Instance);
}
And within AppController.cs
namespace MyApplication
{
public class AppController
{
static AppController _AppController;
public LoginWIndow LoginWIndow;
//Constructor
public void AppController()
{
//Do what you will here, Start login form, bind events, w.e :)
if(true) //Your check
{
ShowLoginWindow();
}
}
public void ShowLoginWindow()
{
LoginWIndow = new LoginWIndow();
LoginWIndow.ClosedForm += new FormClosedEventHander(ExitApplication);
LoginWIndow.Show();
}
public void ExitApplication(Object Sender, FormClosedEventArgs Args)
{
//Some shutdown login Logic, then
Application.Exit();
}
static AppController Instance
{
get
{
if(_AppController == null)
{
_AppController = new AppController();
}
return _AppController;
}
}
}
}