C#-Keinen Close-Button in Winforms anzeigen

private const int CP_NOCLOSE_BUTTON = 0x200;
protected override CreateParams CreateParams
{
    get
    {
       CreateParams myCp = base.CreateParams;
       myCp.ClassStyle = myCp.ClassStyle | CP_NOCLOSE_BUTTON ;
       return myCp;
    }
}
https://stackoverflow.com/questions/7301825/windows-forms-how-to-hide-close-x-button