Hide an external application from taskbar

Question

I've looked through many different forums and I cannot find a way. I am looking to hide external application icons from the taskbar, but not have the application minimized. I have no clue where to start, or how to do it. Any help would be greatly appreciated.

NOTE Hide external application icon, not my form's icon.

Answer 1

You can do this with the ShowWindow function. Here is a small sample, that will hide a running "calc.exe" from your taskbar.

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

internal class Program
{
    /// <summary>Shows a Window</summary>
    /// <remarks>
    /// <para>To perform certain special effects when showing or hiding a 
    /// window, use AnimateWindow.</para>
    ///<para>The first time an application calls ShowWindow, it should use 
    ///the WinMain function's nCmdShow parameter as its nCmdShow parameter. 
    ///Subsequent calls to ShowWindow must use one of the values in the 
    ///given list, instead of the one specified by the WinMain function's 
    ///nCmdShow parameter.</para>
    ///<para>As noted in the discussion of the nCmdShow parameter, the 
    ///nCmdShow value is ignored in the first call to ShowWindow if the 
    ///program that launched the application specifies startup information 
    ///in the structure. In this case, ShowWindow uses the information 
    ///specified in the STARTUPINFO structure to show the window. On 
    ///subsequent calls, the application must call ShowWindow with nCmdShow 
    ///set to SW_SHOWDEFAULT to use the startup information provided by the 
    ///program that launched the application. This behavior is designed for 
    ///the following situations: </para>
    ///<list type="">
    ///    <item>Applications create their main window by calling CreateWindow 
    ///    with the WS_VISIBLE flag set. </item>
    ///    <item>Applications create their main window by calling CreateWindow 
    ///    with the WS_VISIBLE flag cleared, and later call ShowWindow with the 
    ///    SW_SHOW flag set to make it visible.</item>
    ///</list></remarks>
    /// <param name="hWnd">Handle to the window.</param>
    /// <param name="nCmdShow">Specifies how the window is to be shown. 
    /// This parameter is ignored the first time an application calls 
    /// ShowWindow, if the program that launched the application provides a 
    /// STARTUPINFO structure. Otherwise, the first time ShowWindow is called, 
    /// the value should be the value obtained by the WinMain function in its 
    /// nCmdShow parameter. In subsequent calls, this parameter can be one of 
    /// the WindowShowStyle members.</param>
    /// <returns>
    /// If the window was previously visible, the return value is nonzero. 
    /// If the window was previously hidden, the return value is zero.
    /// </returns>
    [DllImport("user32.dll")]
    private static extern bool ShowWindow(IntPtr hWnd, WindowShowStyle nCmdShow);

    /// <summary>Enumeration of the different ways of showing a window using 
    /// ShowWindow</summary>
    private enum WindowShowStyle : uint
    {
        /// <summary>Hides the window and activates another window.</summary>
        /// <remarks>See SW_HIDE</remarks>
        Hide = 0,
        /// <summary>Activates and displays a window. If the window is minimized 
        /// or maximized, the system restores it to its original size and 
        /// position. An application should specify this flag when displaying 
        /// the window for the first time.</summary>
        /// <remarks>See SW_SHOWNORMAL</remarks>
        ShowNormal = 1,
        /// <summary>Activates the window and displays it as a minimized window.</summary>
        /// <remarks>See SW_SHOWMINIMIZED</remarks>
        ShowMinimized = 2,
        /// <summary>Activates the window and displays it as a maximized window.</summary>
        /// <remarks>See SW_SHOWMAXIMIZED</remarks>
        ShowMaximized = 3,
        /// <summary>Maximizes the specified window.</summary>
        /// <remarks>See SW_MAXIMIZE</remarks>
        Maximize = 3,
        /// <summary>Displays a window in its most recent size and position. 
        /// This value is similar to "ShowNormal", except the window is not 
        /// actived.</summary>
        /// <remarks>See SW_SHOWNOACTIVATE</remarks>
        ShowNormalNoActivate = 4,
        /// <summary>Activates the window and displays it in its current size 
        /// and position.</summary>
        /// <remarks>See SW_SHOW</remarks>
        Show = 5,
        /// <summary>Minimizes the specified window and activates the next 
        /// top-level window in the Z order.</summary>
        /// <remarks>See SW_MINIMIZE</remarks>
        Minimize = 6,
        /// <summary>Displays the window as a minimized window. This value is 
        /// similar to "ShowMinimized", except the window is not activated.</summary>
        /// <remarks>See SW_SHOWMINNOACTIVE</remarks>
        ShowMinNoActivate = 7,
        /// <summary>Displays the window in its current size and position. This 
        /// value is similar to "Show", except the window is not activated.</summary>
        /// <remarks>See SW_SHOWNA</remarks>
        ShowNoActivate = 8,
        /// <summary>Activates and displays the window. If the window is 
        /// minimized or maximized, the system restores it to its original size 
        /// and position. An application should specify this flag when restoring 
        /// a minimized window.</summary>
        /// <remarks>See SW_RESTORE</remarks>
        Restore = 9,
        /// <summary>Sets the show state based on the SW_ value specified in the 
        /// STARTUPINFO structure passed to the CreateProcess function by the 
        /// program that started the application.</summary>
        /// <remarks>See SW_SHOWDEFAULT</remarks>
        ShowDefault = 10,
        /// <summary>Windows 2000/XP: Minimizes a window, even if the thread 
        /// that owns the window is hung. This flag should only be used when 
        /// minimizing windows from a different thread.</summary>
        /// <remarks>See SW_FORCEMINIMIZE</remarks>
        ForceMinimized = 11
    }


    private static void Main(string[] args)
    {
        Process[] p = Process.GetProcessesByName("calc"); 

        if(p.Length > 0)
        {
            IntPtr hWnd = p[0].MainWindowHandle;

            ShowWindow(hWnd, WindowShowStyle.Hide);
        }

        Console.ReadLine();
    }
}

Answer 2

There is no really easy way to do this. The ways to have a top-level window not appear in the taskbar are:

1. Make it owned by another window. You cannot do this because the owner is determined at window creation time.
2. Give it the WS_EX_TOOLWINDOW extended window style. You can do this, but it will alter the appearance of the window.
3. Call ITaskbarList::DeleteTab passing the window handle. Whilst this will work, I believe that in some scenarios, the taskbar button will return.

Essentially, what you are attempting to do is against the rules. Don't be surprised if the system doesn't make it easy for you to tamper with other applications.