How To Make a Windows Form App Truly Full Screen (and Hide Taskbar) in C#

• Download demo project - 13.65 KB

Introduction

One of the sounds-like-simple questions is “how to make your application truly Full Screen”, i.e. not showing Taskbar or anything like that.

The initial approach is obvious...

targetForm.WindowState = FormWindowState.Maximized;
targetForm.FormBorderStyle = FormBorderStyle.None;
targetForm.TopMost = true;

... assuming that the target form is referenced with targetForm.

Does it work? Well, sort of. If your Taskbar has default setting unchecked for “Keep the taskbar on top of other Windows”, this will present your application in all its glory all over the screen estate.

However, if the Taskbar is set to appear on top of all others, this won't help - your application won't cover it.

Update For This Approach

In the discussion of the article (below) Azlan David (thanks David!) suggested to try this approach:

targetForm.FormBorderStyle = FormBorderStyle.None;
targetForm.WindowState = FormWindowState.Maximized;

(Just changed the order of property assignments.) It does the work on all Win XP SP2 computers where I had the opportunity to test it; however, on one Win 2003 SP1 computer, this did not help; I'm still investigating why.

Let’s go further - the next step is to use P/Invoke and to engage the Win32 API services. There is an easy way to hide a particular window. So, find the Taskbar and hide it:

private const int SW_HIDE = 0;
private const int SW_SHOW = 1;

[DllImport("user32.dll")]
private static extern int FindWindow(string className, string windowText);
[DllImport("user32.dll")]
private static extern int ShowWindow(int hwnd, int command);

int hWnd = FindWindow("Shell_TrayWnd", "");
ShowWindow(hWnd, SW_HIDE);

targetForm.WindowState = FormWindowState.Maximized;
targetForm.FormBorderStyle = FormBorderStyle.None;
targetForm.TopMost = true;

(You need to add using System.Runtime.InteropServices;)

Is this better? In theory, yes - the Taskbar is hidden, but your application still does not occupy the whole screen - the place where the Taskbar was is not used.

The real and proven solution is to make a request to WinAPI that your form take the whole screen estate - Taskbar will hide itself in that case. Full information about that can be found in the KB article Q179363: How To Cover the Task Bar with a Window.

The steps are as follows:

• Find out the dimension of the screen estate by calling GetSystemMetrics
• Set the dimensions of your form to full screen

Here is the actual code:

/// <summary>
/// Selected Win API Function Calls
/// </summary>

public class WinApi
{
    [DllImport("user32.dll", EntryPoint = "GetSystemMetrics")]
    public static extern int GetSystemMetrics(int which);

    [DllImport("user32.dll")]
    public static extern void
        SetWindowPos(IntPtr hwnd, IntPtr hwndInsertAfter,
                     int X, int Y, int width, int height, uint flags);        

    private const int SM_CXSCREEN = 0;
    private const int SM_CYSCREEN = 1;
    private static IntPtr HWND_TOP = IntPtr.Zero;
    private const int SWP_SHOWWINDOW = 64; // 0×0040

    public static int ScreenX
    {
        get { return GetSystemMetrics(SM_CXSCREEN);}
    }

    public static int ScreenY
    {
        get { return GetSystemMetrics(SM_CYSCREEN);}
    }

    public static void SetWinFullScreen(IntPtr hwnd)
    {
        SetWindowPos(hwnd, HWND_TOP, 0, 0, ScreenX, ScreenY, SWP_SHOWWINDOW);
    }
}

/// <summary>
/// Class used to preserve / restore / maximize state of the form
/// </summary>
public class FormState
{
    private FormWindowState winState;
    private FormBorderStyle brdStyle;
    private bool topMost;
    private Rectangle bounds;

    private bool IsMaximized = false;

    public void Maximize(Form targetForm)
    {
        if (!IsMaximized)
        {
            IsMaximized = true;
            Save(targetForm);
            targetForm.WindowState = FormWindowState.Maximized;
            targetForm.FormBorderStyle = FormBorderStyle.None;
            targetForm.TopMost = true;
            WinApi.SetWinFullScreen(targetForm.Handle);
        }
    }

    public void Save(Form targetForm)
    {
        winState = targetForm.WindowState;
        brdStyle = targetForm.FormBorderStyle;
        topMost = targetForm.TopMost;
        bounds = targetForm.Bounds;
    }

    public void Restore(Form targetForm)
    {
        targetForm.WindowState = winState;
        targetForm.FormBorderStyle = brdStyle;
        targetForm.TopMost = topMost;
        targetForm.Bounds = bounds;
        IsMaximized = false;
    }
}

Now you can use the above class in your WinForms application like this:

public partial class MaxForm : Form
{
    FormState formState = new FormState();

    public MaxForm()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        formState.Maximize(this);
    }

    private void button2_Click(object sender, EventArgs e)
    {
        formState.Restore(this);
    }
}

The full code and example application can be downloaded from the link at the top of this article.

History

• 3^rd December, 2006: Initial post