Prevent form from going into windowed mode

Question

I want to create a new form, which is set to maximized. It should show the title bar and the taskbar. This wasn't a big problem so far. When i set this.MaximizeBox = false; the button on the title bar gets disabled but if I drag or double click the title bar the form goes into window mode (tested on Windows 7).

Setting MinimumSize and MaximumSize to the same value wasn't successful.

Answer 1

public class Form1 {
  public Form1(){
      InitializeComponent();
      WindowState = FormWindowState.Maximized;
      Load += (s,e) => {
         MaximizeBox = false;        
      };
  }
  bool hitControlButtons;
  protected override void WndProc(ref Message m)
  {
     if ((!hitControlButtons) && (m.Msg == 0xa3 || m.Msg == 0xa1))//WM_NCLBUTTONDBLCLK and WM_NCLBUTTONDOWN
     {                
        return;
     }
     if (m.Msg == 0xA0)//WM_NCMOUSEMOVE
     {
        int wp = m.WParam.ToInt32();                
        hitControlButtons = wp == 8 || wp == 20 || wp == 9;//Mouse over MinButton, CloseButton, MaxButton                               
     }
     base.WndProc(ref m);            
  }
}