This article describes an approach to displaying transparent forms in a Windows
application. Such may be useful to
anyone wishing to display an odd shaped form for a splash screen or possibly a
tool dialog with a transparent background.
Figure 1: Transparent Forms
The solution contains three Windows Form classes; each shows something different
about a transparent form.
Figure 2: Solution
Explorer with the Project Visible
There is nothing much to creating the transparent form; setting the forms back
color and transparency key property value to the same color is all that is
required. In form 1 the form back color and transparency key are both set to
lime green; this color does not occur within the image and so the image will not
appear to have holes in it; do not use a transparency color that occurs in your
images. That much takes care of making
the form transparent. Setting
the forms FormBorderStyle property to none removes the forms border and all that
will remain when the form is displayed is an image.
Figure 3: Forms
Transparency Key Property
Of course having a transparent borderless form eliminates the ability to drag
the form around the desktop; at least without doing a bit more work. In order to
set up the form for dragging in this condition a couple of DLL call are needed.
The following contains the code behind the Form1 class.
following user32.DLL calls (SendMessage and ReleaseCapture) are required to
support the dragging and dropping of the form in the absense of a caption bar on
The SendMessage function sends a message to a window or windows.
Declare Auto Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr,
ByVal msg As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr
ReleaseCapture releases a mouse capture
Declare Function ReleaseCapture Lib "user32.dll" () As Boolean
picturebox fills the entire draggable area of the form (those
sections which are not visible cannot be used for a drag operation) and for that
that reason the picture box controls mouse down event is used to support the
borderless form dragging operations.
Handles form drags
Private Sub pictureBox1_MouseDown(ByVal sender As System.Object, ByVal e
As System.Windows.Forms.MouseEventArgs) Handles pictureBox1.MouseDown
= MouseButtons.Left Then
&HA1, &H2, 2)
of the class code is pretty straightforward and is not particularly relevant to
the topic. The code is annotation to explain the remaining event handlers.
Open new instance of form 2
Private Sub button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handlesbutton2.Click
Dim f As New Form2()
Open new instance of form 3
Private Sub button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handlesbutton3.Click
Dim f As New Form3()
Dispose main form and exit
Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handlesbutton1.Click
Form 2 (Form2.vb)
The code behind Form2 is the same as it used in Form1; the only differences
between the two forms are the complexity of the image used as the borderless
form and that the background color and transparency key property values are
different than that used on Form1.
Form 3 (Form3.cs)
Form3 is another spin on the same thing used in forms 1 and 2. The
difference here is that the picture box contains a white rectangle; the
transparency key value is set also to white which will defeat any attempts to
drag the form. This form does have a
border around it to enable dragging the form, if you set the border style to
Ã¢â‚¬Å“NoneÃ¢â‚¬Â then the form will no longer be draggable.
This article was intended to demonstrate an approach to creating transparent
backed, borderless, draggable forms. The
approach may be used to generate some sort of custom UI or may be used to build
a classier looking splash screen.