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Painless Persistence of Windows Forms Positions

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21 May 2008CPOL4 min read 42.1K   330   27   18
A no-pain way of retaining your Windows Form positions between application runs.


This is a simple drop-in component that will retain the bounds and state of a window between sessions of an application.


A common task in developing desktop applications is remembering where the user put their forms in the last application run. Some users spend a great deal of time setting up their workspace exactly right, and it is quite an unpleasant experience to realise the application doesn't remember their hard work.

Using the Code

To use the code, follow these steps:

  1. Simply add a reference to the RememberFormPosition assembly, or include the source in your own project
  2. Open the designer for your Windows Form of choice
  3. From the toolbox, add a RememberFormPosition component

And that is all there is to it.

Points of Interest

Where Data is Stored

The position and state information for each form is stored in the Registry in the Application.UserAppDataRegistry key. The following Registry entries will be created:

  • FormName_Left
  • FormName_Top
  • FormName_Right
  • FormName_Bottom
  • FormName_State

Where FormName is the name of the form or the custom name that is provided to the control.

When the Data is Read in

The RememberFormPosition component implements the ISupportInitialize interface, and we do the reading of the form state in the EndInit() implementation.

Doing this in EndEdit() ensures that

  • The form is not yet visible, so no update flickering can take place. For example, if we did this on the FormLoad event instead, we would see the window move around as it has already been made visible.
  • The Form property of the RememberFormPosition component is set up.
public void EndInit()
  _form.StartPosition = FormStartPosition.Manual;
                                                UseFormName ? _form.Name : StorageName);

When is the Information Written

During the initialization of the RememberFormPosition component, we attach an event handler to our form's FormClosing event. During this, we write out the form's position and state. This is done because it ensures the form has not been disposed yet and all the information we need is in a valid state.

How are Minimized and Maximized Windows Handled

The special cases of a form being maximized or minimized needs to be handled carefully, because using the ordinary Control.Bounds will not achieve the desired result. In the case of being maximized, it will be the extends of the current Screen.WorkingArea, and in the case of minimized, it may be very small and will not be useful.

So when our Form.WindowState is not FormWindowState.Normal, we do the following:

  • Look at the Form.RestoreBounds property
  • This Form.RestoreBounds property is relative to Screen.PrimaryScreen.WorkingArea, so we need to compute the desktop bounds for this
  • We then write out the current WindowState

The function that handles this is RemeberFormPositionUtils.SaveFormPlacement().

public static void SaveFormPlacement(RegistryKey key, Form form, string name)
  if (form.WindowState == FormWindowState.Normal)
    key.SetRectangleValue(name, form.DesktopBounds);
    Rectangle workingArea = Screen.PrimaryScreen.WorkingArea;
    Rectangle restoreBounds = form.RestoreBounds;
    restoreBounds.X -= workingArea.X;
    restoreBounds.Y -= workingArea.Y;
    key.SetRectangleValue(name, restoreBounds);
  key.SetWindowStateValue(name, form.WindowState);

When reading these back in, we:

  • Set Form.StartPosition to FormStartPosition.Manual
  • Set the WindowState to FormWindowState.Normal
  • We then set form bounds by using Form.SetDesktopBounds()
  • After this, we change Form.WindowState to the state stored in the Registry

The code that handles this is primarily in RemeberFormPositionUtils.RestoreFormPlacement().

public static void RestoreFormPlacement(RegistryKey key, Form form, string name)
  Rectangle? rect = key.GetRectangleValue(name);

  if (rect.HasValue)
    Rectangle formBounds = rect.Value;

    if (!form.IsMdiChild)
      formBounds = EnsureFitsInDesktop(formBounds);

    form.WindowState = FormWindowState.Normal;
    form.SetDesktopBounds(formBounds.X, formBounds.Y, 
                          formBounds.Width, formBounds.Height);

  FormWindowState? state = key.GetWindowStateValue(name);

  if (state.HasValue)
    form.WindowState = state.Value;

Extension Methods

A small portion of the code makes use of Extension Methods to read and write values from the Registry. It is hardly a necessary thing, but it was just something to experiment with.

If you wish to use the code in a C# 2.0 compiler, it should be a trivial task to remove the extra this keywords and just refer to the static classes explicitly.

Multiple Monitors

Multiple monitors has not been tested, but preliminary code has been put in place to handle it. If all four corners of the form are out of an available Screen, then we place the form in the middle of the screen. Also, if the form is too big to fit on the screen, we resize it so it is just under the size of the working area.

Things Learned About Components and WinForms in General

Designer Serialized Properties

When exposing properties that are [Browsable(true)], ensure that if you have a [DefaultValue] attribute, you also set up this default value in your constructor! If you do not, then if these conditions are true:

  • Your property value is the same as your DefaultValue.
  • Your DefaultValue is different from the default compiler value.

Then your property value will not get serialized and it will very confusingly lose your value. This happens because in designer serialized code, if a property value equals a DefaultValue, then the value is not written out as part of serialization. And hence next time the designer appears and your object is instantiated, it will revert to the compiler generated value.

Discovering the Owner of a Component

This was not as straightforward a task as I would have imagined. Components to not have direct knowledge of the Component or Control they are a part of.

In order to achieve this, a simple ComponentDesigner needed to be created in order to initialise our RememberFormPosition.Form property to the current Form. Inside ComponentDesigner.Initialize(), we have the ability to enquire what component we are designing via the ComponentDesigner.ParentComponent property.


  • 21/05/2008 - First article version.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By
Software Developer (Senior) BitPlex Pty Ltd
Australia Australia
A professional developer in the Mining sector since 2000, Phil has a passion for creating robust, quality scientific applications.

I have started a software company, BitPlex, and I am focused on created a new and unique small business project planning tool called GamePlan.

My major fields of interest in software are 3D applications, visualisation, scheduling and optimisation, and novel UI design. My goal as a professional developer is to help people solve real world problems through reliable and fun to use software.

Comments and Discussions

GeneralYet another congratulation message Pin
Tiago Freitas Leal13-May-09 5:07
professionalTiago Freitas Leal13-May-09 5:07 
Hi Phil,

There a lot of utilities to re-open a window with the same size and on the position. As you said, your's is the easiest one to use I've ever seen (just drag and drop). Congratulations.

Having said that, there are a few point you could improve.

1. Remove .NET 3 dependency
The is no need for it and limits the use of the component.

2. The component should refuse to drop on anything else than forms
If I drop it on a Control, it will stay there, but the Control will crash when it opens.

3. Persist to file and not to registry

4. Make the storage location configurable

Right now it is being stored in

4.1. Using Version should be an option
Note that Company, Product and Version are the taken from the assembly (although I can say if it's the file version or the assembly version). This means that if I change the Version, all the settings will be gone.

4.2. Allow storage per form instance
The UseFormName/StorageName properties are intended for using the same storage for all the instances of a form. On a MDI environement I can open several instances of the same form and want to tile them. When I go home and come back next morning, I will find out that my nice tiling is lost and I must do it again.
Optionally use the Text property of the form instance would solve this problem.
GeneralRe: Yet another congratulation message Pin
Phil Martin13-May-09 12:24
professionalPhil Martin13-May-09 12:24 
GeneralRe: Yet another congratulation message Pin
Tiago Freitas Leal13-May-09 13:33
professionalTiago Freitas Leal13-May-09 13:33 
GeneralRe: Yet another congratulation message Pin
Tiago Freitas Leal23-May-09 0:39
professionalTiago Freitas Leal23-May-09 0:39 
GeneralChange of storage Pin
dactivo11-Nov-08 0:40
dactivo11-Nov-08 0:40 
GeneralRe: Change of storage Pin
Phil Martin11-Nov-08 9:55
professionalPhil Martin11-Nov-08 9:55 
GeneralSuggestion Pin
Björn Friedrich18-Jul-08 13:06
Björn Friedrich18-Jul-08 13:06 
GeneralInteresting subject Pin
Grommel21-May-08 5:09
Grommel21-May-08 5:09 
GeneralRe: Interesting subject Pin
Phil Martin21-May-08 12:31
professionalPhil Martin21-May-08 12:31 
RantRegistry in Vista Pin
Itay Sagui21-May-08 5:00
Itay Sagui21-May-08 5:00 
GeneralRe: Registry in Vista Pin
Phil Martin21-May-08 12:30
professionalPhil Martin21-May-08 12:30 
GeneralI have seen this done before Pin
Sacha Barber21-May-08 4:15
Sacha Barber21-May-08 4:15 
GeneralRe: I have seen this done before Pin
Phil Martin21-May-08 12:29
professionalPhil Martin21-May-08 12:29 
GeneralRe: I have seen this done before Pin
Sacha Barber21-May-08 21:11
Sacha Barber21-May-08 21:11 
GeneralMissing download Pin
Marc Clifton21-May-08 2:47
mvaMarc Clifton21-May-08 2:47 
GeneralRe: Missing download Pin
Phil Martin21-May-08 3:55
professionalPhil Martin21-May-08 3:55 
GeneralNo source code Pin
leppie21-May-08 2:47
leppie21-May-08 2:47 
GeneralRe: No source code Pin
Phil Martin21-May-08 3:53
professionalPhil Martin21-May-08 3:53 

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