Show or hide a title bar on demand

I just found an easier solution that is working great for me during runtime. This question was posted a long time ago, but maybe somebody else will find this helpful.

The eureka for me was learning to set the form's ControlBox property to false. Note too that the text property must be empty.

    Dim f As New Form
    f.Text = String.Empty
    f.ControlBox = False
    f.Show(Me)

From this page, to do it at writing time:

form1.borderstyle = 0 (None), 1 (Fixed Single), 2 (Sizeable), 3 (Fixed Dialog), 4 (Fixed Toolwindow), 5 (Sizeable Toolwindow)

However, to turn on/off at runtime is much harder, see the reasoning and the example of how to do so Here

To ensure the routine works on both 32 and 64 bit systems, you need to do a little extra checking. In cases like these, I use reflector to have a look at how the framework implements the pinvokes. In particular, have a look at System.Windows.Forms.SafeNativeMethods and System.Windows.Forms.UnSafeNativeMethods.

Below is the code I use which takes advantage of extension methods.

'See: System.Windows.Forms.SafeNativeMethods.SetWindowPos
<DllImport("user32.dll", CharSet:=CharSet.Auto, ExactSpelling:=True)> _
Private Function SetWindowPos(ByVal hWnd As HandleRef, ByVal hWndInsertAfter As HandleRef, ByVal x As Integer, ByVal y As Integer, ByVal cx As Integer, ByVal cy As Integer, ByVal flags As Integer) As Boolean
End Function

'See: System.Windows.Forms.UnSafeNativeMethods.GetWindowLong*
<DllImport("user32.dll", EntryPoint:="GetWindowLong", CharSet:=CharSet.Auto)> _
Private Function GetWindowLong32(ByVal hWnd As HandleRef, ByVal nIndex As Integer) As IntPtr
End Function

<DllImport("user32.dll", EntryPoint:="GetWindowLongPtr", CharSet:=CharSet.Auto)> _
Private Function GetWindowLongPtr64(ByVal hWnd As HandleRef, ByVal nIndex As Integer) As IntPtr
End Function

Private Function GetWindowLong(ByVal hWnd As HandleRef, ByVal nIndex As Integer) As IntPtr
    If (IntPtr.Size = 4) Then
        Return GetWindowLong32(hWnd, nIndex)
    End If
    Return GetWindowLongPtr64(hWnd, nIndex)
End Function

'See: System.Windows.Forms.UnSafeNativeMethods.SetWindowLong*
<DllImport("user32.dll", EntryPoint:="SetWindowLong", CharSet:=CharSet.Auto)> _
Private Function SetWindowLongPtr32(ByVal hWnd As HandleRef, ByVal nIndex As Integer, ByVal dwNewLong As HandleRef) As IntPtr
End Function

<DllImport("user32.dll", EntryPoint:="SetWindowLongPtr", CharSet:=CharSet.Auto)> _
Private Function SetWindowLongPtr64(ByVal hWnd As HandleRef, ByVal nIndex As Integer, ByVal dwNewLong As HandleRef) As IntPtr
End Function

Private Function SetWindowLong(ByVal hWnd As HandleRef, ByVal nIndex As Integer, ByVal dwNewLong As HandleRef) As IntPtr
    If (IntPtr.Size = 4) Then
        Return SetWindowLongPtr32(hWnd, nIndex, dwNewLong)
    End If
    Return SetWindowLongPtr64(hWnd, nIndex, dwNewLong)
End Function

'See: System.Windows.Forms.Control.SetWindowStyle
Private Sub SetWindowStyle(ByVal form As Form, ByVal flag As Integer, ByVal value As Boolean)
    Dim windowLong As Integer = CInt(CLng(GetWindowLong(New HandleRef(form, form.Handle), -16)))
    Dim ip As IntPtr
    If value Then
        ip = New IntPtr(windowLong Or flag)
    Else
        ip = New IntPtr(windowLong And Not flag)
    End If
    SetWindowLong(New HandleRef(form, form.Handle), -16, New HandleRef(Nothing, ip))
End Sub

<Extension()> _
Public Sub ShowCaption(ByVal form As Form)
    SetWindowStyle(form, &H400000, True)
    ApplyStyleChanges(form)
End Sub

<Extension()> _
Public Sub HideCaption(ByVal form As Form)
    SetWindowStyle(form, &H400000, False)
    ApplyStyleChanges(form)
End Sub

<Extension()> _
Public Function ApplyStyleChanges(ByVal form As Form) As Boolean
    Return SetWindowPos(New HandleRef(form, form.Handle), NullHandleRef, 0, 0, 0, 0, &H37)
End Function