How do I make a WinForms app go Full Screen

I have a WinForms app that I am trying to make full screen (somewhat like what VS does in full screen mode).

Currently I am setting FormBorderStyle to None and WindowState to Maximized which gives me a little more space, but it doesn't cover over the taskbar if it is visible.

What do I need to do to use that space as well?

For bonus points, is there something I can do to make my MenuStrip autohide to give up that space as well?

To the base question, the following will do the trick (hiding the taskbar)

private void Form1_Load(object sender, EventArgs e)
{
    this.TopMost = true;
    this.FormBorderStyle = FormBorderStyle.None;
    this.WindowState = FormWindowState.Maximized;
}

But, interestingly, if you swap those last two lines the Taskbar remains visible. I think the sequence of these actions will be hard to control with the properties window.

#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: https://stackoverflow.com/questions/2272019/how-to-display-a-windows-form-in-full-screen-on-top-of-the-taskbar)

And for the menustrip-question, try set

MenuStrip1.Parent = Nothing

when in fullscreen mode, it should then disapear.

And when exiting fullscreenmode, reset the menustrip1.parent to the form again and the menustrip will be normal again.

You can use the following code to fit your system screen and task bar is visible.

    private void Form1_Load(object sender, EventArgs e)
    {   
        // hide max,min and close button at top right of Window
        this.FormBorderStyle = FormBorderStyle.None;
        // fill the screen
        this.Bounds = Screen.PrimaryScreen.Bounds;
    }
    

No need to use:

    this.TopMost = true;
    

That line interferes with alt+tab to switch to other application. ("TopMost" means the window stays on top of other windows, unless they are also marked "TopMost".)

I recently made a Mediaplayer application and I used API calls to make sure the taskbar was hidden when the program was running fullscreen and then restored the taskbar when the program was not in fullscreen or not had the focus or was exited.

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Integer
Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Integer, ByVal hWnd2 As Integer, ByVal lpsz1 As String, ByVal lpsz2 As String) As Integer
Private Declare Function ShowWindow Lib "user32" (ByVal hwnd As Integer, ByVal nCmdShow As Integer) As Integer

Sub HideTrayBar()
	Try


		Dim tWnd As Integer = 0
		Dim bWnd As Integer = 0
		tWnd = FindWindow("Shell_TrayWnd", vbNullString)
		bWnd = FindWindowEx(tWnd, bWnd, "BUTTON", vbNullString)
		ShowWindow(tWnd, 0)
		ShowWindow(bWnd, 0)
	Catch ex As Exception
		'Error hiding the taskbar, do what you want here..'
	End Try
End Sub
Sub ShowTraybar()
	Try
		Dim tWnd As Integer = 0
		Dim bWnd As Integer = 0
		tWnd = FindWindow("Shell_TrayWnd", vbNullString)
		bWnd = FindWindowEx(tWnd, bWnd, "BUTTON", vbNullString)
		ShowWindow(bWnd, 1)
		ShowWindow(tWnd, 1)
	Catch ex As Exception
	    'Error showing the taskbar, do what you want here..'
    End Try


End Sub

I worked on Zingd idea and made it simpler to use.

I also added the standard F11 key to toggle fullscreen mode.

Setup

Everything is now in the FullScreen class, so you don't have to declare a bunch of variables in your Form. You just instanciate a FullScreen object in your form's constructor :

FullScreen fullScreen;

public Form1()
{
    InitializeComponent();
    fullScreen = new FullScreen(this);
}

Please note this assumes the form is not maximized when you create the FullScreen object.

Usage

You just use one of the classe's functions to toggle the fullscreen mode :

fullScreen.Toggle();

or if you need to handle it explicitly :

fullScreen.Enter();
fullScreen.Leave();

Code

using System.Windows.Forms;


class FullScreen
{ 
    Form TargetForm;

    FormWindowState PreviousWindowState;

    public FullScreen(Form targetForm)
    {
        TargetForm = targetForm;
        TargetForm.KeyPreview = true;
        TargetForm.KeyDown += TargetForm_KeyDown;
    }

    private void TargetForm_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.KeyData == Keys.F11)
        {
            Toggle();
        }
    }

    public void Toggle()
    {
        if (TargetForm.WindowState == FormWindowState.Maximized)
        {
            Leave();
        }
        else
        {
            Enter();
        }
    }
        
    public void Enter()
    {
        if (TargetForm.WindowState != FormWindowState.Maximized)
        {
            PreviousWindowState = TargetForm.WindowState;
            TargetForm.WindowState = FormWindowState.Normal;
            TargetForm.FormBorderStyle = FormBorderStyle.None;
            TargetForm.WindowState = FormWindowState.Maximized;
        }
    }
      
    public void Leave()
    {
        TargetForm.FormBorderStyle = FormBorderStyle.Sizable;
        TargetForm.WindowState = PreviousWindowState;
    }
}

You need to set your window to be topmost.

I don't know if it will work on .NET 2.0, but it worked me on .NET 4.5.2. Here is the code:

using System;
using System.Drawing;
using System.Windows.Forms;

public partial class Your_Form_Name : Form
{
    public Your_Form_Name()
    {
        InitializeComponent();
    }

    // CODE STARTS HERE

    private System.Drawing.Size oldsize = new System.Drawing.Size(300, 300);
    private System.Drawing.Point oldlocation = new System.Drawing.Point(0, 0);
    private System.Windows.Forms.FormWindowState oldstate = System.Windows.Forms.FormWindowState.Normal;
    private System.Windows.Forms.FormBorderStyle oldstyle = System.Windows.Forms.FormBorderStyle.Sizable;
    private bool fullscreen = false;
    /// <summary>
    /// Goes to fullscreen or the old state.
    /// </summary>
    private void UpgradeFullscreen()
    {
        if (!fullscreen)
        {
            oldsize = this.Size;
            oldstate = this.WindowState;
            oldstyle = this.FormBorderStyle;
            oldlocation = this.Location;
            this.WindowState = System.Windows.Forms.FormWindowState.Normal;
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
            this.Bounds = System.Windows.Forms.Screen.PrimaryScreen.Bounds;
            fullscreen = true;
        }
        else
        {
            this.Location = oldlocation;
            this.WindowState = oldstate;
            this.FormBorderStyle = oldstyle;
            this.Size = oldsize;
            fullscreen = false;
        }
    }

    // CODE ENDS HERE
}

Usage:

UpgradeFullscreen(); // Goes to fullscreen
UpgradeFullscreen(); // Goes back to normal state
// You don't need arguments.

> Notice: You MUST place it inside your Form's class (Example: partial class Form1 : Form { /* Code goes here */ } ) or it will not work because if you don't place it on any form, code this will create an exception.

On the Form Move Event add this:

private void Frm_Move (object sender, EventArgs e)
{
    Top = 0; Left = 0;
    Size = new System.Drawing.Size(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);
}

If you want to keep the border of the form and have it cover the task bar, use the following:

Set FormBoarderStyle to either FixedSingle or Fixed3D

Set MaximizeBox to False

Set WindowState to Maximized