Opening form's context menu - vb.net

Question

I wanted to add a dropdown with a few options(shortcuts) next to the minimize button on my forms. To that end I followed the following example on Code Project https://www.codeproject.com/Articles/55180/Extending-the-Non-Client-Area-in-Aero.
This worked perfectly for what I wanted (I considered hiding the Border style but then I wouldnt be able to Dock the form on the edges of the screen) but for some reason disabled the ability to call the context menu on the title bar.
I noticed in the example that the WM_NCHITTEST event's override was not using the HTSYSMENU result and only returned HTCAPTION for the entire area of the title bar. I then changed the code to return the correct value if the mouse was on the left side of the title bar and with this I managed to call the context menu by left clicking on that corner.
Dim p As New Point(LoWord(CInt(lparam)), HiWord(CInt(lparam)))
Dim cap As Rectangle = RectangleToScreen(New Rectangle(0, dwmMargins.cxLeftWidth, Width, dwmMargins.cyTopHeight - dwmMargins.cxLeftWidth))
If cap.Contains(p) Then
Dim mp As Point = MousePosition
mp = PointToClient(mp)
If mp.X < 30 Then
Return New IntPtr(HTSYSMENU)
Else
Return New IntPtr(HTCAPTION)
End If
End If
I can't however find how to activate the call to the context menu when right clicking anywhere on the title bar.
I tried overriding the message WM_NCRBUTTONUP on WndProc and send a message to show the Context Menu but nothing seems to happen.
Dim WM_CONTEXTMENU As Integer = &H7B
If m.Msg = WM_NCRBUTTONUP Then
Dim mp As Point = MousePosition
mp = PointToClient(mp)
Dwm.SendMessage(Me.Handle, WM_CONTEXTMENU, Me.Handle, Dwm.MAKEWPARAM(mp.Y, mp.X))
<DllImport("user32.dll")>
Public Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As UInteger, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer
End Function
I believe that I'm trying to reinvent the wheel and that I shouldn't need to be handling the WM_NCRBUTTONUP message to call the context menu since it should be handled automatically but I haven't found any information about it online.

Answer 1

As an option, you can handle WM_NCRBUTTONUP and send a WM_POPUPSYSTEMMENU:
case WM_NCRBUTTONUP:
{
SendMessage(this.Handle, 0x313/*WM_POPUPSYSTEMMENU*/, (IntPtr)0, m.LParam);
break;
}
And this signature of SendMessage which I used:
[DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);