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Simple Popup Control

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26 Mar 2013LGPL35 min read 1M   24.4K   521   243
How to create a custom pop-up control in C#.
Sample application using a custom popup control:

Custom popup control

Another application using a custom tooltip...

Custom tooltip

... and a more complex popup that can be resized:

Resizable popup

Tracking popup opening below the specified part of a control:

Tracking popup

Cascade of popup controls:

Cascade of popup controls


Popup windows are everywhere. Each tooltip is a popup window; each combobox has its popup list; many advertisements are also shown in popup windows.

How to Create a Popup Control in .NET?

At first, we might choose the Form class as a base class for our popup control. Unfortunately, it is a bad choice because when we show our popup form, the parent form loses its focus. A popup window should not cause that. Luckily, there is a class that does not cause loss of focus. We can use it as a base class for our popup control. It is the ToolStripDropDown class.

How to Use the ToolStripDropDown Class?

This would be the simplest way, without deriving from that class:

ToolStripDropDown popup = new ToolStripDropDown();
popup.Margin = Padding.Empty;
popup.Padding = Padding.Empty;
ToolStripControlHost host = new ToolStripControlHost(content);
host.Margin = Padding.Empty;
host.Padding = Padding.Empty;
popup.Show(parentForm, location);

In this case, content is a control we want to show in a popup window. Of course, we have to remember to later dispose the popup window and its contents.

Popup Class

I wrote a Popup class that derives from ToolStripDropDown and simplifies the creating and managing of popup windows. The class calculates by itself where it should "pop" on the screen. It also disposes itself immediately after disposing the content control. To show a popup with a button, for example, we could write:

new Popup(new Button()).Show(someControl);

Here, someControl would be a control below which we want to show our popup.

Popup Resizing

To enable resizing for your popup, you must set the Resizable property to true and add the following code into your content control class:

protected override void WndProc(ref Message m)
    if ((Parent as Popup).ProcessResizing(ref m)) return;
    base.WndProc(ref m);

You also have to set the ResizeRedraw property of the content control to true.


To specify the minimum and maximum size of the content control, please use the following properties:

  • content.MinimumSize and content.MaximumSize only inside the constructor of the content control
  • popup.MinimumSize and popup.MaximumSize elsewhere

ComboBox Class

The System.Windows.Forms.ComboBox class behaves in a strange way when it is on a popup control. It closes the popup control when the user clicks on a part of the combobox's dropdown that sticks out of a popup. So, I have created a PopupControl.ComboBox class that behaves properly.

PopupComboBox Class

This is a base class for comboboxes that can have a custom dropdown attached.

Animation Support

Animation is enabled by default. To change it, set the AnimationDuration, HidingAnimation, and ShowingAnimation properties.

Popup Members


  • AcceptAlt — Gets or sets a value indicating whether pressing the Alt key should close the popup.
  • AnimationDuration — Determines the duration of the animation.
  • Content — Gets the content of the popup.
  • FocusOnOpen — Gets or sets a value indicating whether the content should receive the focus after the popup has been opened.
  • HidingAnimation — Determines which animation to use while hiding the popup window.
  • MaximumSize — Gets or sets a maximum size of the popup.
  • MinimumSize — Gets or sets a minimum size of the popup.
  • NonInteractive — Gets or sets a value indicating whether the popup acts like a transparent windows; e.g., it cannot be clicked (note — it does not affect child controls).
  • Resizable — Gets or sets a value indicating whether the popup is resizable.
  • ShowingAnimation — Determines which animation to use while showing the popup window.


  • Popup(Control content) — Initializes a new instance of the Popup class.


  • void PaintSizeGrip(PaintEventArgs e) — Paints the sizing grip.
  • bool ProcessResizing(ref Message m) — Processes the resizing messages.
  • void Show(Control control) — Shows the popup window below the specified control.
  • void Show(Control control, Rectangle area) — Shows the popup window below the specified area of the specified control.


  • Base class for custom tooltips.
  • Office 2007-like tooltip class.


  • 1.5 (20.10.2010) — Important! This is the last “standalone” version of the control. The next version is included in a new project hosted at CodePlex.
    • Added the NonInteractive property to the Popup class.
    • Fixed resizing on DualView/multi monitor systems.
    • Popup is now always shown on top of other windows (previously the popup could be shown below its parent during the animation process).
    • PopupComboBox didn’t properly set focus to its dropdown on Windows 7.
    • Improved compatibility with Mono.
    • Uses C# 3.0 syntax (auto-properties, lambdas).
    • Signed binaries for both .NET 2.0 and .NET 4.0 are available.
    • Solution upgraded to the Visual C# 2010 format.
    • License changed to LGPL 3.0.
  • 1.4 (16.01.2009)
    • Added the DroppedDown property, and the DropDown, DropDownClosed events to the PopupComboBox class.
    • Fixed resizing of a popup when the MaximumSize property of the content control is not set.
  • 1.3.1 (20.09.2008)
    • Tab-key properly transfers the focus between controls contained in a popup window.
    • Minor bugs fixed.
  • 1.3 (04.05.2008)
    • Added the AnimationDuration, HidingAnimation, and ShowingAnimation properties.
    • Removed the UseFadeEffect property.
    • Popup control can animate now even when the FocusOnOpen property is set to false.
  • 1.2.5 (24.01.2008)
    • Fixed “Alt+F4” bug.
    • Fixed drawing the sizing grip.
    • Minor bugs fixed.
  • 1.2 (24.07.2007)
    • Added animation support.
    • Added AcceptAlt property.
    • Clicking on the non-client area bug fixed.
    • Minor bugs fixed.
  • 1.1 (05.07.2007)
    • Added XML documentation.
    • "Fixed" the ComboBox class, so it can be used inside a popup.
    • Added base class for a combobox that can have a custom dropdown, PopupComboBox.
    • The sizing grip is automatically drawn if a popup is resizable.
    • Added support for a minimum and maximum size of a resizable popup.
    • Minor bugs fixed.
  • 1.0
    • 08.06.2007 – Added resizing support and capability for using cascading pop-ups.
    • 06.02.2007 – Added keyboard and custom region support, and the ShowForControl method name changed to Show.
    • 03.02.2007 – First version.


This article, along with any associated source code and files, is licensed under The GNU Lesser General Public License (LGPLv3)

Written By
Software Developer
Poland Poland
I am a graduate of Wroclaw University of Science and Technology, Poland.

My interests: gardening, reading, programming, drawing, Japan, Spain.

Comments and Discussions

GeneralContextMenuStrip Pin
sg200529-Jul-08 22:07
sg200529-Jul-08 22:07 
GeneralRe: ContextMenuStrip Pin
seeblunt11-Nov-08 1:23
seeblunt11-Nov-08 1:23 
QuestionProblem resizing... Pin
Christopher Stratmann16-Jul-08 2:48
Christopher Stratmann16-Jul-08 2:48 
QuestionRe: Problem resizing... Pin
Polish Sausage16-Apr-19 8:14
Polish Sausage16-Apr-19 8:14 
GeneralThanks Pin
Ali Rafiee30-Jun-08 7:34
Ali Rafiee30-Jun-08 7:34 
Generalcapture Escape keydown Pin
hamid_m29-Jun-08 21:31
hamid_m29-Jun-08 21:31 
GeneralRe: capture Escape keydown Pin
Lukasz Sw.20-Jul-08 8:32
Lukasz Sw.20-Jul-08 8:32 
GeneralLove the control but the code is kinda hard to follow.... Pin
Christopher Stratmann15-Jun-08 17:52
Christopher Stratmann15-Jun-08 17:52 
		private bool <big>_resizable</big>;
		private bool <big>resizable</big>;
		/// <summary>
		/// Gets or sets a value indicating whether the <see cref="PopupControl.Popup" /> is able to resize.
		/// </summary>
		/// <value><c>true</c> if able to resize; otherwise, <c>false</c>.</value>
		public bool Resizable {
			get { return resizable && _resizable; }
			set { resizable = value; }

You have two private variables for resizable? I think _resizable could be changed to _ownerPopupResizable.
GeneralRe: Love the control but the code is kinda hard to follow.... Pin
Lukasz Sw.20-Jul-08 7:50
Lukasz Sw.20-Jul-08 7:50 
GeneralRe: Love the control but the code is kinda hard to follow.... Pin
PerfectlyNormalBeast22-Aug-08 7:52
PerfectlyNormalBeast22-Aug-08 7:52 
GeneralRe: Love the control but the code is kinda hard to follow.... Pin
Lukasz Sw.22-Aug-08 8:50
Lukasz Sw.22-Aug-08 8:50 
GeneralDateTime.Now edge case Pin
toidy28-May-08 22:45
toidy28-May-08 22:45 
GeneralRe: DateTime.Now edge case Pin
Lukasz Sw.20-Jul-08 7:45
Lukasz Sw.20-Jul-08 7:45 
GeneralSuppressUnmanagedCodeSecurity Pin
toidy28-May-08 20:12
toidy28-May-08 20:12 
GeneralRe: SuppressUnmanagedCodeSecurity Pin
Lukasz Sw.20-Jul-08 7:41
Lukasz Sw.20-Jul-08 7:41 
GeneralTab Key Pin
SamNaseri27-May-08 0:53
SamNaseri27-May-08 0:53 
GeneralRe: Tab Key Pin
Jimcheng30-May-08 4:34
Jimcheng30-May-08 4:34 
GeneralRe: Tab Key Pin
I'm Chris8-Jun-08 1:43
professionalI'm Chris8-Jun-08 1:43 
GeneralRe: Tab Key Pin
Lukasz Sw.20-Jul-08 5:29
Lukasz Sw.20-Jul-08 5:29 
GeneralRe: Tab Key Pin
Lukasz Sw.20-Jul-08 5:27
Lukasz Sw.20-Jul-08 5:27 
GeneralRe: Tab Key Pin
Lukasz Sw.20-Jul-08 5:33
Lukasz Sw.20-Jul-08 5:33 
GeneralActivateOnShow Pin
Jonathan C Dickinson18-May-08 6:12
Jonathan C Dickinson18-May-08 6:12 
GeneralSlide effect Pin
User 36104232-May-08 11:33
User 36104232-May-08 11:33 
GeneralRe: Slide effect Pin
Lukasz Sw.3-May-08 6:28
Lukasz Sw.3-May-08 6:28 
QuestionFocus Pin
iPodSync23-Apr-08 9:55
iPodSync23-Apr-08 9:55 

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