Do Not give this function the handle of the desktop!

C# Signature:

[DllImport("user32.dll")]
static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

VB Signature:

<DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
Private Shared Function ShowWindow(ByVal hwnd As IntPtr, ByVal nCmdShow As Int32) As Boolean
End Function

Constants:

SW

User-Defined Types:

None.

Notes:

None.

Tips & Tricks:

Please add some!

Sample Code:

/// <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
}
//...In your code some where: show a form, without making it active
ShowWindow(this.Handle, WindowShowStyle.ShowNoActivate);

Alternative Managed API:

- It's possible to use, in some cases, the ShowInTaskbar form's property.

- Override the ShowWithoutActivation property and make it always return true.

  protected override bool ShowWithoutActivation
  {
     get { return true; }
  }
  // Do not set the TopMost property to true, as this will give the form focus when calling Show.
  // It is still not possible to make the form top most and showing it without activating it.
  // I do not know how, anyway.

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