Disable close button on Title Bar in vb.net

place this code in the form code

'declare constant
Private Const DIS_CLOSE_BUTTON As Integer = &H200

'code
    Protected Overloads Overrides ReadOnly Property CreateParams() As CreateParams
        Get
            Dim p As CreateParams = MyBase.CreateParams
            p.ClassStyle = p.ClassStyle Or DIS_CLOSE_BUTTON
            '   p.ClassStyle = p.ClassStyle Or &H200
            Return p  
        End Get
    End Property