ShowInTaskbarをFalseに設定した時の挙動

BUG: The icon that represents your form appears as a blank form icon in Visual C# .NET if you set the ShowInTaskBar property to False

SYMPTOMS
You set the ShowInTaskBar property of a Microsoft Windows form to False. When you press the ALT+TAB key combination to move the control focus from the form to any other program, the icon that represents your form appears as a blank form icon.

WORKAROUND
To make sure that the correct icon appears when you press the ALT+TAB key combination to move the control focus from the form to any other program while the ShowInTaskbar property is set to False, use the following code.

コード:

using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; using System.Runtime.InteropServices; namespace WindowsApplication1 { /// <summary> /// Summary description for Form1. /// </summary> public class Form1 : System.Windows.Forms.Form { /// <summary> /// Required designer variable. /// </summary> private System.ComponentModel.Container components = null; public Form1() { // // Required for Windows Form Designer support // InitializeComponent(); // // TODO: Add any constructor code after InitializeComponent call // } /// <summary> /// Clean up any resources being used. /// </summary> protected override void Dispose( bool disposing ) { if( disposing ) { if (components != null) { components.Dispose(); } } base.Dispose( disposing ); } #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() { System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(Form1)); // // Form1 // this.AutoScaleBaseSize = new System.Drawing.Size(5, 13); this.ClientSize = new System.Drawing.Size(292, 266); this.Icon = ((System.Drawing.Icon)(resources.GetObject("$this.Icon"))); this.Name = "Form1"; this.ShowInTaskbar = false; this.Text = "Form1"; this.Load += new System.EventHandler(this.Form1_Load); } #endregion /// <summary> /// The main entry point for the application. /// </summary> [STAThread] static void Main() { Application.Run(new Form1()); } [DllImport("user32.dll")] private static extern int SendMessage(IntPtr hwnd, int message, int wParam, IntPtr lParam); [DllImport("user32.dll", ExactSpelling=true)] private static extern IntPtr GetWindow(IntPtr hwnd, int cmd); private IntPtr GetTopLevelOwner(Control c) { IntPtr hwndOwner = c.Handle; IntPtr hwndCurrent = c.Handle; while (hwndCurrent != (IntPtr)0) { hwndCurrent = GetWindow(hwndCurrent, GW_OWNER); if (hwndCurrent != (IntPtr)0) { hwndOwner = hwndCurrent; } } return hwndOwner; } private const int WM_SETICON = 0x80; private const int GW_OWNER = 4; private const int ICON_SMALL = 0; private const int ICON_BIG = 1; private void Form1_Load(object sender, System.EventArgs e) { SendMessage(GetTopLevelOwner(this), WM_SETICON, ICON_BIG, this.Icon.Handle); } private void Form1_Closed(object sender, System.EventArgs e) { SendMessage(GetTopLevelOwner(this), WM_SETICON, ICON_BIG, new IntPtr(0)); } } }

STATUS
Microsoft has confirmed that this is a bug in the Microsoft products that are listed in the "Applies to" section.

Joe Report As Irrelevant
Written: 6/10/2005 1:02 PM
This appears to work ok, except when I wish my app to start in minimized mode, and am using an NotifyIcon component, I don't want the application icon to show up in the Alt+Tab listing unless the actual form is visible... If I put the initial SendMessage in my Form_Loading event, then the icon shows up in the Alt+Tab list...

清華さんの書き込み (2006-01-12 15:48) より:

僕のところからは問題なく飛べますが…なぜでしょうか？

一応引用しておきますね

SetWindowLongを使い、タイトルバーのないウインドウで、Alt+Tab時のアイコン
を非表示にすることに成功しました。