[c#] How to display a Windows Form in full screen on top of the taskbar?

I have a .net windows application that needs to run in full screen. When the application starts however the taskbar is shown on top of the main form and it only disappears when activating the form by clicking on it or using ALT-TAB. The form's current properties are as follow:

• WindowState=FormWindowState.Normal
• TopMost=Normal
• Size=1024,768 (this is the screen resolution of the machines it's going to be running on)
• FormBorderStyle = None

I've tried adding the followings on form load but none worked for me:

• this.Focus(); (after giving the focus this.Focus property is always false)
• this.BringToFront();
• this.TopMost = true; (this however would not be ideal in my scenario)
• this.Bounds = Screen.PrimaryScreen.Bounds;
• this.Bounds = Screen.PrimaryScreen.Bounds;

Is there a way to do it within .NET or would I have to invoke native windows methods and if so a code snippet would very much be appreciated.

many thanks

I've tried so many solutions, some of them works on Windows XP and all of them did NOT work on Windows 7. After all I write a simple method to do so.

private void GoFullscreen(bool fullscreen)
    {
        if (fullscreen)
        {
            this.WindowState = FormWindowState.Normal;
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
            this.Bounds = Screen.PrimaryScreen.Bounds;
        }
        else
        {
            this.WindowState = FormWindowState.Maximized;
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Sizable;
        }
    }

the order of code is important and will not work if you change the place of WindwosState and FormBorderStyle.

One of the advantages of this method is leaving the TOPMOST on false that allow other forms to come over the main form.

It absolutely solved my problem.

This is how I make forms full screen.

private void button1_Click(object sender, EventArgs e)
{
    int minx, miny, maxx, maxy;
    inx = miny = int.MaxValue;
    maxx = maxy = int.MinValue;

    foreach (Screen screen in Screen.AllScreens)
    {
        var bounds = screen.Bounds;
        minx = Math.Min(minx, bounds.X);
        miny = Math.Min(miny, bounds.Y);
        maxx = Math.Max(maxx, bounds.Right);
        maxy = Math.Max(maxy, bounds.Bottom);
    }

    Form3 fs = new Form3();
    fs.Activate();
    Rectangle tempRect = new Rectangle(1, 0, maxx, maxy);
    this.DesktopBounds = tempRect;
}

A tested and simple solution

I've been looking for an answer for this question in SO and some other sites, but one gave an answer was very complex to me and some others answers simply doesn't work correctly, so after a lot code testing I solved this puzzle.

Note: I'm using Windows 8 and my taskbar isn't on auto-hide mode.

I discovered that setting the WindowState to Normal before performing any modifications will stop the error with the not covered taskbar.

The code

I created this class that have two methods, the first enters in the "full screen mode" and the second leaves the "full screen mode". So you just need to create an object of this class and pass the Form you want to set full screen as an argument to the EnterFullScreenMode method or to the LeaveFullScreenMode method:

class FullScreen
{
    public void EnterFullScreenMode(Form targetForm)
    {
        targetForm.WindowState = FormWindowState.Normal;
        targetForm.FormBorderStyle = FormBorderStyle.None;
        targetForm.WindowState = FormWindowState.Maximized;
    }

    public void LeaveFullScreenMode(Form targetForm)
    {
        targetForm.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Sizable;
        targetForm.WindowState = FormWindowState.Normal;
    }
}

Usage example

    private void fullScreenToolStripMenuItem_Click(object sender, EventArgs e)
    {
        FullScreen fullScreen = new FullScreen();

        if (fullScreenMode == FullScreenMode.No)  // FullScreenMode is an enum
        {
            fullScreen.EnterFullScreenMode(this);
            fullScreenMode = FullScreenMode.Yes;
        }
        else
        {
            fullScreen.LeaveFullScreenMode(this);
            fullScreenMode = FullScreenMode.No;
        }
    }

I have placed this same answer on another question that I'm not sure if is a duplicate or not of this one. (Link to the other question: How do I make a WinForms app go Full Screen)

FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
WindowState = FormWindowState.Maximized;

FormBorderStyle = FormBorderStyle.Sizable;
TopMost = false;
WindowState = FormWindowState.Normal;

THIS CODE MAKE YOUR WINDOWS FULL SCREEN THIS WILL ALSO COVER WHOLE SCREEN

I believe that it can be done by simply setting your FormBorderStyle Property to None and the WindowState to Maximized. If you are using Visual Studio both of those can be found in the IDE so there is no need to do so programmatically. Make sure to include some way of closing/exiting the program before doing this cause this will remove that oh so helpful X in the upper right corner.

EDIT:

Try this instead. It is a snippet that I have kept for a long time. I can't even remember who to credit for it, but it works.

/*
 * A function to put a System.Windows.Forms.Form in fullscreen mode
 * Author: Danny Battison
 * Contact: [email protected]
 */

        // a struct containing important information about the state to restore to
        struct clientRect
        {
            public Point location;
            public int width;
            public int height;
        };
        // this should be in the scope your class
        clientRect restore;
                bool fullscreen = false;

        /// <summary>
        /// Makes the form either fullscreen, or restores it to it's original size/location
        /// </summary>
        void Fullscreen()
        {
            if (fullscreen == false)
            {
                this.restore.location = this.Location;
                this.restore.width = this.Width;
                this.restore.height = this.Height;
                this.TopMost = true;
                this.Location = new Point(0,0);
                this.FormBorderStyle = FormBorderStyle.None;
                this.Width = Screen.PrimaryScreen.Bounds.Width;
                this.Height = Screen.PrimaryScreen.Bounds.Height;
            }
            else
            {
                this.TopMost = false;
                this.Location = this.restore.location;
                this.Width = this.restore.width;
                this.Height = this.restore.height;
                                // these are the two variables you may wish to change, depending
                                // on the design of your form (WindowState and FormBorderStyle)
                this.WindowState = FormWindowState.Normal;
                this.FormBorderStyle = FormBorderStyle.Sizable;
            }
        }

I'm not have an explain on how it works, but works, and being cowboy coder is that all I need.

        System.Drawing.Rectangle rect = Screen.GetWorkingArea(this);
        this.MaximizedBounds = Screen.GetWorkingArea(this);
        this.WindowState = FormWindowState.Maximized;

Use:

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

And then your form is placed over the taskbar.