Minimizing a window to the System Tray on a Close event

Buz & Skup — Sat, 26 Mar 2005 12:02:00 GMT

A question that .Net programmers does frequently ask is the following : how to minimize a window in the systray when the user clicks the "Close" button ? This post exposes solutions to the various problems this quite simple need implies.

The first step is to prevent the window to close. This can be done either by handling the Closing event or by overriding the OnClosing protected virtual method. For performance and memory consumption reasons, I'd prefer not to use event handlers whenever possible. The code is quite simple since whe only need to cancel the operation, and looks like the following...

Code Copy

///
     <summary>

     /// Occurs when the window is requested to be 
     closed.
/// </summary>

     /// <param name="e">The 
     event arguments</param>
protected override
     void OnClosing(CancelEventArgs e)

    {// The window must only be 
      minimized in tray

     e.Cancel = true;

     MinimizeInTray();

     

     base.OnClosing(e);

    }

... and the MinimizeInTray method must do the following:

Minimize the window,
Hide the window item in the taskbar.

Code Copy

private
     void MinimizeInTray()

    {this.ShowInTaskbar =
      false;

     this.WindowState = FormWindowState.Minimized;

    }

Now, supposing that you have a context menu attached to the NotifyIcon object that represents the systray icon for your application, you can add the following menu items:

An openMenu menu item that restores the window,

Code Copy

private
     void openMenu_Click(object sender, 
    System.EventArgs e)

    {ShowFromTray();

    }

private void ShowFromTray()

    {this.WindowState = 
     FormWindowState.Normal;

     this.ShowInTaskbar = true;

    }

And an exitMenu item that closes the application.

Code Copy

private
     void exitMenu_Click(object sender, 
    System.EventArgs e)

    {Application.Exit();

    }

Note that calling Close() fails because our OnClosing method prevents the window to close...

Now, we should think that our job is completed. But (yes, there's always a but in programming), what happens if the computer is being shutdown ? The answer is quite simple : our OnClosing implementation prevents the window to be closed, which prevents the computer to be shutdown...

To solve this issue, we need some lightweight Interop :

First, override the WndProc virtual method to handle the WM_QUERYENDSESSION message:

Code Copy

private
     const int WM_QUERYENDSESSION = 0x11;
private bool endSessionPending;

     

     protected override void
    WndProc(ref Message m)

    {if (m.Msg == 
     WM_QUERYENDSESSION)endSessionPending =
       true;

     base.WndProc(ref m);

    }

Then, modify the OnClosing method to handle the event in a different way :

Code Copy HideScrollFull

///
     <summary>

     /// Occurs when the window is requested to be 
     closed.
/// </summary>

     /// <param name="e">The 
     event arguments</param>
protected override
     void OnClosing(CancelEventArgs e)

    {if (endSessionPending)

     {// The session is ending.

      e.Cancel = false;

     }
else

     {// The window must only be 
       minimized in tray

      e.Cancel = true;

      MinimizeInTray();

     }

base.OnClosing(e);

    }

And that's all!

The full C# sample code is available below. There's only missing icon resources, but you will correct them by yourself!

Code Copy HideScrollFull

#region
    References

using System;
using System.ComponentModel;
using System.Windows.Forms;
using System.Security.Permissions;

#endregion

     

     namespace MinimizeOnClose

    {/// <summary>
/// Represents the main window 
      of the application.
/// </summary>
public class MinimizeOnClose 
     : System.Windows.Forms.Form

     {#region Interop 
      Constants

private const
       int WM_QUERYENDSESSION = 0x11;

#endregion

       

       #region Fields

private System.Windows.Forms.NotifyIcon 
      notifyIcon;
private System.Windows.Forms.ContextMenu 
      notifyIconMenu;
private System.Windows.Forms.MenuItem openMenu;
private System.Windows.Forms.MenuItem hideMenu;
private System.Windows.Forms.MenuItem exitMenu;
private System.ComponentModel.IContainer 
      components;
private System.Windows.Forms.MenuItem blankMenu;

private bool endSessionPending;

#endregion

       

       #region Instance Management

public MinimizeOnClose()

      {InitializeComponent();

      }

#endregion

       

       #region Protected Overrides

/// <summary>
/// Cleans all the resources.
/// </summary>
protected override
       void Dispose(bool disposing)

      {if (disposing)

       {if (components !=
         null)components.Dispose();

       }
base.Dispose(disposing);

      }

/// <summary>
/// Occurs when the window is 
       requested to be closed.
/// </summary>
/// <param 
       name="e">The event arguments</param>
protected override
       void OnClosing(CancelEventArgs e)

      {if (endSessionPending)

       {// The session is ending

        e.Cancel = false;

       }
else

       {// The window must only be 
         minimized in tray

        e.Cancel = true;

        MinimizeInTray();

       }

base.OnClosing(e);

      }
[SecurityPermission(SecurityAction.LinkDemand, 
       UnmanagedCode=true)]

      protected override void
      WndProc(ref Message m)

      {if (m.Msg == 
       WM_QUERYENDSESSION)endSessionPending =
         true;

       base.WndProc(ref m);

      }
#endregion

      

      #region Private Members

#region Event Handlers

private void openMenu_Click(object
      sender, System.EventArgs e)

      {ShowFromTray();

      }

private void hideMenu_Click(object
      sender, System.EventArgs e)

      {MinimizeInTray();

      }

private void exitMenu_Click(object
      sender, System.EventArgs e)

      {Application.Exit();

      }

#endregion

       

       #region Private Methods

private void MinimizeInTray()

      {this.ShowInTaskbar =
        false;

       this.WindowState = FormWindowState.Minimized;

       

       openMenu.Visible = true;

       hideMenu.Visible = false;

      }

private void ShowFromTray()

      {this.WindowState = 
       FormWindowState.Normal;

       this.ShowInTaskbar = true;

       

       openMenu.Visible = true;

       hideMenu.Visible = false;

      }

#endregion

       

       #region Windows Form Designer generated code

/// <summary>
/// Required method for Designer 
       support - do not modify
/// the contents of this method 
       with the code editor.
/// </summary>
private void InitializeComponent()

      {this.components =
        new System.ComponentModel.Container();

       System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(MinimizeOnClose));
this.notifyIcon = new 
       System.Windows.Forms.NotifyIcon(this.components);
this.notifyIconMenu = new
       System.Windows.Forms.ContextMenu();
this.openMenu = new System.Windows.Forms.MenuItem();
this.hideMenu = new System.Windows.Forms.MenuItem();
this.blankMenu = new System.Windows.Forms.MenuItem();
this.exitMenu = new System.Windows.Forms.MenuItem();
//
// notifyIcon
//
this.notifyIcon.ContextMenu = this.notifyIconMenu;
this.notifyIcon.Icon = 
       ((System.Drawing.Icon)(resources.GetObject("notifyIcon.Icon")));
this.notifyIcon.Text = 
       "MinimizeOnClose";
this.notifyIcon.Visible = true;
//
// notifyIconMenu
//
this.notifyIconMenu.MenuItems.AddRange(new
       System.Windows.Forms.MenuItem[] {this.openMenu,

        this.hideMenu,

        this.blankMenu,

        this.exitMenu});

       //
// openMenu
//
this.openMenu.Index = 0;
this.openMenu.Text = "&Open";
this.openMenu.Visible = false;
this.openMenu.Click += new
       System.EventHandler(this.openMenu_Click);
//
// hideMenu
//
this.hideMenu.Index = 1;
this.hideMenu.Text = "&Hide";
this.hideMenu.Click += new
       System.EventHandler(this.hideMenu_Click);
//
// blankMenu
//
this.blankMenu.Index = 2;
this.blankMenu.Text = "-";
//
// exitMenu
//
this.exitMenu.Index = 3;
this.exitMenu.Text = "E&xit";
this.exitMenu.Click += new
       System.EventHandler(this.exitMenu_Click);
//
// MinimizeOnClose
//
this.AutoScaleBaseSize = new
       System.Drawing.Size(5, 13);
this.ClientSize = new 
       System.Drawing.Size(240, 78);
this.Icon = 
       ((System.Drawing.Icon)(resources.GetObject("$this.Icon")));
this.Name = "MinimizeOnClose";
this.Text = "MinimizeOnClose";

      }
#endregion

      
/// <summary>
/// The application entry point.
/// </summary>

      [STAThread]
static void Main()

      {Application.Run(new MinimizeOnClose());

      }

#endregion

     }

    }

. . .

Have a nice week-end, and do not overindulge in Easter eggs too much!