How to make Windows Form app truly Full Screen (and to hide Taskbar) in C#?

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

Initial approach is obvious:


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

Does it work? Well, sort of. If your Taskbar have default setting unchecked for “Keep the taskbar on top of other windows”, this will present your application in all it’s glory all over 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.

Let’s go further – next step is to use P/Invoke and to engage Win32 API services. There is easy way to hide 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 – Taskbar is hidden, but your application still does not occupy whole screen – place where Taskbar was is not used.

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


/// <summary>
/// Selected Win AI 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; // 0x0040
    
    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 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;
    }
}

Code for example application is here: MaxWinForm.zip

51 thoughts on “How to make Windows Form app truly Full Screen (and to hide Taskbar) in C#?”

  1. Thanks a lot, very useful!

    I tried to store last window state as boolean var in user settings (normal / fullscreen) and to restore the state after new program launch. Surprisingly the window in normal mode had no title bar…
    Add initial values made the solution:
    private FormWindowState winState = FormWindowState.Normal;
    private FormBorderStyle brdStyle = FormBorderStyle.Sizable;

    If using dialogs or messageboxes they are shown in the background and make the GUI unusable.
    Therefore I removed all “topMost” items:
    //private bool topMost = false;
    See also comment 35.
    Now it works really fine for me with Win7!

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