How do combo boxes, when displaying list items, intercept mouse events to anywhere on the form to hide the list?

Question

I\'m trying to implement a .net form control with functionality similar to a combo box, but I don\'t know the proper method to intercept mouse events anywhere on the form to

Answer 1

Control.Capture

As explained in the documentation, you now "Own" the mouse (until someone else captures it - though that's bad form). You receive all mouse messages and can handle a "Down" not on your control to dismiss.

Answer 2

Just use a ToolStripControlHost along with the ToolStripDropDown, and it will work just like the ComboBox dropdown. You won't have to worry about handling the mouse events.

I've used this before:

Private Sub ShowControl(ByVal fromControl As Control, ByVal whichControl As Control)
  '\\ whichControl needs MinimumSize set:'
  whichControl.MinimumSize = whichControl.Size

  Dim toolDrop As New ToolStripDropDown()
  Dim toolHost As New ToolStripControlHost(whichControl)
  toolHost.Margin = New Padding(0)
  toolDrop.Padding = New Padding(0)
  toolDrop.Items.Add(toolHost)
  toolDrop.Show(Me, New Point(fromControl.Left, fromControl.Bottom))
End Sub

Quick Demo with a Button control on a form:

Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
  ShowControl(Button1, New MonthCalendar)
End Sub

To answer the question in your title, I think the pinvoke calls of SetCapture and Release Capture are used to handle that type of functionality.