If the ControlBox property is set to true, the control box is displayed in the upper-left corner of the caption bar. The control box is where the user can click to access the system menu.

If you set ControlBox to false, and also set the Location property, the Size property of Form will not update to reflect that the non-client area of the form has been hidden. To fix this problem, put the code which alters the Location property to the HandleCreated event.

Note
When set to false, the ControlBox property has no effect on a Multiple-document interface (MDI) child form that is displayed maximized at time of creation.

The following code example uses the ControlBox, FormBorderStyle, MaximizeBox, MinimizeBox, and StartPosition properties to create a form that does not have any border or caption box. The form created in this example could be used to create a splash screen for an application. The example requires that the example's method is defined in a form class and called when the form is being initialized.

Public Sub CreateMyBorderlesWindow()
    FormBorderStyle = FormBorderStyle.None
    MaximizeBox = False
    MinimizeBox = False
    StartPosition = FormStartPosition.CenterScreen
    ' Remove the control box so the form will only display client area.
    ControlBox = False
End Sub 'CreateMyBorderlesWindow

public void CreateMyBorderlessWindow()
 {
    this.FormBorderStyle = FormBorderStyle.None;
    this.MaximizeBox = false;
    this.MinimizeBox = false;
    this.StartPosition = FormStartPosition.CenterScreen;
    // Remove the control box so the form will only display client area.
    this.ControlBox = false;
 }
 

public:
   void CreateMyBorderlessWindow()
   {
      this->FormBorderStyle = ::FormBorderStyle::None;
      this->MaximizeBox = false;
      this->MinimizeBox = false;
      this->StartPosition = FormStartPosition::CenterScreen;
      // Remove the control box so the form will only display client area.
      this->ControlBox = false;
   }

.NET Framework

.NET Framework Client Profile

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference