[c#] Maximize a window programmatically and prevent the user from changing the windows state

How do I maximize a window programmatically so that it cannot be resized once it reaches the maximized state (for example, maximize Internet Explorer and see it)?

I set FormWindowState property as

this.WindowState = FormWindowState.Maximized;
this.MaximizedBounds = (x,y);

but it doesn't work. How do I do this?

The window I want to maximize is a window in my application.

Change the property WindowState to System.Windows.Forms.FormWindowState.Maximized, in some cases if the older answers doesn't works.

So the window will be maximized, and the other parts are in the other answers.

When I do this, I get a very small square screen instead of a maxed screen. Yet, when I only use the FormWindowState.Maximized, it does give me a full screen. Why is that?

        public partial class Testscherm : Form
    {
            public Testscherm()

            {

                    this.WindowState = FormWindowState.Maximized;
                    this.MaximizeBox = false;
                    this.MinimizeBox = false;
                    this.MinimumSize = this.Size;
                    this.MaximumSize = this.Size;
                    this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle;
                    InitializeComponent();


            }

To programmatically maximize the windowstate you can use:

 this.WindowState = FormWindowState.Maximized;
 this.MaximizeBox = false;

To stop the window being resizeable once you've maximised it you need to change the FormBorderStyle from Sizable to one of the fixed constants:

FixedSingle
Fixed3D
FixedDialog

From the MSDN Page Remarks section:

The border style of the form determines how the outer edge of the form appears. In addition to changing the border display for a form, certain border styles prevent the form from being sized. For example, the FormBorderStyle.FixedDialog border style changes the border of the form to that of a dialog box and prevents the form from being resized. The border style can also affect the size or availability of the caption bar section of a form.

It will change the appearance of the form if you pick Fixed3D for example, and you'll probably have to do some work if you want the form to restore to non-maximised and be resizeable again.

When your form is maximized, set its minimum size = max size, so user cannot resize it.

    this.WindowState = FormWindowState.Maximized;
    this.MinimumSize = this.Size;
    this.MaximumSize = this.Size;

You were close... after your code of

WindowState = FormWindowState.Maximized;

THEN, set the form's min/max size capacity to the value once its sized out.

MinimumSize = this.Size;
MaximumSize = this.Size;