Show or Hide Windows

by Feb 27, 2017

PowerShell can call internal Windows API functions, and in this example, we’d like to show how you can change the show state of an application window. You’ll be able to maximize, minimize, hide, or show, for example.

The example uses PowerShell 5’s new enum capability to give the showstate numbers meaningful names. In older versions of PowerShell, simply remove the enum, and use the appropriate showstate numbers directly in the code.

The key learning point here is how to use Add-Type to take a C#-style signature of an API method and return a type that exposes this method to your PowerShell code:

#requires -Version 5
# this enum works in PowerShell 5 only
# in earlier versions, simply remove the enum,
# and use the numbers for the desired window state
# directly

Enum ShowStates
  Hide = 0
  Normal = 1
  Minimized = 2
  Maximized = 3
  ShowNoActivateRecentPosition = 4
  Show = 5
  MinimizeActivateNext = 6
  MinimizeNoActivate = 7
  ShowNoActivate = 8
  Restore = 9
  ShowDefault = 10
  ForceMinimize = 11

# the C#-style signature of an API function (see also
$code = '[DllImport("user32.dll")] public static extern bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);'

# add signature as new type to PowerShell (for this session)
$type = Add-Type -MemberDefinition $code -Name myAPI -PassThru

# access a process
# (in this example, we are accessing the current PowerShell host
#  with its process ID being present in $pid, but you can use
#  any process ID instead)
$process = Get-Process -Id $PID

# get the process window handle
$hwnd = $process.MainWindowHandle

# apply a new window size to the handle, i.e. hide the window completely
$type::ShowWindowAsync($hwnd, [ShowStates]::Hide)

Start-Sleep -Seconds 2
# restore the window handle again
$type::ShowWindowAsync($hwnd, [ShowStates]::Show)

Note how this example temporarily hides the PowerShell window for 2 seconds. You can now do the same to any running application window. Just use Get-Process to find the target process, and use its property “MainWindowHandle” to send the showstate change request.

Some applications manage multiple windows. In this case, you can only target the primary window or else would have to resort to additional API functions to first get a hold of the window handle of the child window.

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