Force to close MessageBox programmatically

问题:

Let me give you the background.

We have an Application(medium sized) that is using MessageBox.Show (....) at various places (in hundreds).

These message boxes are part of workflow and being used for informing,warning or taking input from an user. Application is supposed to automatically log off after certain time if there is no activity. We have a requirement that while logging out the application, just to clean the session data , to clear views and to hide itself so that in next launch, it won't have to execute the startup process which is costly in terms of time.

Everything is working fine but in a scenario when there is some message box on the screen and user left the machine without responding to message box and then due to no activity to make the application to log out. Problem is Message box won't disappear.

How I can close the opened messagebox, if any, while hiding the application?

回答1:

Here is a piece of code based on UIAutomation (a cool but still not very used API) that attempts to close all modal windows (including the one opened with MessageBox) of the current process:

    /// <summary>
    /// Attempt to close modal windows if there are any.
    /// </summary>
    public static void CloseModalWindows()
    {
        // get the main window
        AutomationElement root = AutomationElement.FromHandle(Process.GetCurrentProcess().MainWindowHandle);
        if (root == null)
            return;

        // it should implement the Window pattern
        object pattern;
        if (!root.TryGetCurrentPattern(WindowPattern.Pattern, out pattern))
            return;

        WindowPattern window = (WindowPattern)pattern;
        if (window.Current.WindowInteractionState != WindowInteractionState.ReadyForUserInteraction)
        {
            // get sub windows
            foreach (AutomationElement element in root.FindAll(TreeScope.Children, new PropertyCondition(AutomationElement.ControlTypeProperty, ControlType.Window)))
            {
                // hmmm... is it really a window?
                if (element.TryGetCurrentPattern(WindowPattern.Pattern, out pattern))
                {
                    // if it's ready, try to close it
                    WindowPattern childWindow = (WindowPattern)pattern;
                    if (childWindow.Current.WindowInteractionState == WindowInteractionState.ReadyForUserInteraction)
                    {
                        childWindow.Close();
                    }
                }
            }
        }
    }

For example, if you have a WinForms application that pops up a MessageBox when you press some button1, you will still be able to close the app using Windows "Close Window" menu (right click in the task bar):

    private void button1_Click(object sender, EventArgs e)
    {
        MessageBox.Show("Don't click me. I want to be closed automatically!");
    }

    protected override void WndProc(ref System.Windows.Forms.Message m)
    {
        const int WM_SYSCOMMAND = 0x0112;
        const int SC_CLOSE = 0xF060;

        if (m.Msg == WM_SYSCOMMAND) // this is sent even if a modal MessageBox is shown
        {
            if ((int)m.WParam == SC_CLOSE)
            {
                CloseModalWindows();
                Close();
            }
        }
        base.WndProc(ref m);
    }

You could use CloseModalWindows somewhere else in your code of course, this is just a sample.

回答2:

This link on MSDN forums shows how to close a message box by using FindWindow and sending a WM_CLOSE message. Although the question was asked for .NET/WindowsCE, it might solve your problem, its worth a look

回答3:

First a Question: If messages boxes are used as part of workflow, won't programatically closing message box cause the flow to change/continue?

I think you have three options

1. Create your own version of the messagebox class that opens a dialog window that looks like a messagebox with added functionality so it closed automatically after a period of time.

2. Implement something like this in c# to close message boxes programtically. http://www.codeproject.com/KB/dialog/AutoCloseMessageBox.aspx

3. Get rid of the message boxes from interupting the workflow. This is probably the best solution as from the sound of it closing a message box programatically will cause workflow to continue/change, and perhaps even cause another messagebox to show which may not be desirable. But obviously fixing the root problem might be best, but isn't always the easiest.

1 and 2 would need to be done from a separate thread, so you will need to think about the implications of that as showing the messagebox will be blocking.

回答4:

Heres my example with SendKeys - tested and working:

lets say we have backgroundworker and button in form. After button was click - start worker and show message box. In workers DoWork event sleep for 5s and then send enter key - messsage box closed.

private void button1_Click(object sender, EventArgs e)
{
    backgroundWorker1.RunWorkerAsync();
    MessageBox.Show("Close this message!");
}

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    Thread.Sleep(5000);
    SendKeys.SendWait("{Enter}");//or Esc
}

回答5:

Taking as an assumption that you can edit the code that's calling the MessageBox.Show() method, I would recommend not use MessageBox. Instead, just use your own custom form, calling ShowDialog() on it to do basically the same thing as the MessageBox class. Then, you have the instance of the form itself, and you can call Close() on that instance to close it.

A good example is here.

回答6:

I think the cleanest way would be to implement you own message box form like

class MyMessageBox : Form {
  private MyMessageBox currentForm; // The currently active message box

  public static Show(....) { // same as MessageBox.Show
    // ...
  }

  public static Show(...) { // define additional overloads
  }

  public static CloseCurrent() {
    if (currentForm != null)
      currentForm.Close();
  }

  // ...
}

In some of my larger projects, I found this approach useful also for other purposes (such as automatic logging of error messages etc.)

The second idea I have would be to use GetTopWindow() (or maybe some other WIN32 function) to get the current top-level window of your application and send a WM_CLOSE message to it.

回答7:

I used .net 2 and two approaches with the same trick.

Open the MessageBox from stub-Form with MessageBox.Show(this,"message")

When the form is not visible or doesn't has really UI.

1. Keep the form handler and close it with:

   static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
   

   or

2. holding the form as class parameter and using FormX.Close().

Since the Form is the owner of the MessageBox, Closing it will close the MessageBox.

回答8:

Refer to DmitryG post in "Close a MessageBox after several seconds"

Auto-Close MessageBox after timeout reach

using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;

    public class AutoClosingMessageBox
    {
        System.Threading.Timer _timeoutTimer;
        string _caption;
        AutoClosingMessageBox(string text, string caption, int timeout)
        {
            _caption = caption;
            _timeoutTimer = new System.Threading.Timer(OnTimerElapsed,
                null, timeout, System.Threading.Timeout.Infinite);
            MessageBox.Show(text, caption);
        }
        public static void Show(string text, string caption, int timeout)
        {
            new AutoClosingMessageBox(text, caption, timeout);
        }
        void OnTimerElapsed(object state)
        {
            IntPtr mbWnd = FindWindow(null, _caption);
            if (mbWnd != IntPtr.Zero)
                SendMessage(mbWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
            _timeoutTimer.Dispose();
        }
        const int WM_CLOSE = 0x0010;
        [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
        [System.Runtime.InteropServices.DllImport("user32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
        static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
    }

and Call it via

AutoClosingMessageBox.Show("Content", "Title", TimeOut);

回答9:

Create your own control for this and implement behavior you like to have there. As an option there may be a timer to close this MessageBox.