How to Activate the pervious active Window in VB? - vb.net

Question

I am trying to create a windows form app using visual studio to capture the screen shot of an active window application. I created a capture button which captures the form itself and not the Previous active window. Thus i want to toggle to the previous active window and a screen shoot should be captured considering that as the current active window. I am relatively new to VB. kindly help me out with this issue.
thank you.

Answer 1

One approach is to prevent your Form from getting Focus, thus keeping the "previous" form as the active selected one.
See WS_EX_NOACTIVATE:
A top-level window created with this style does not become the
foreground window when the user clicks it.
Public Class Form1
Private Structure RECT
Public Left As Integer
Public Top As Integer
Public Right As Integer
Public Bottom As Integer
End Structure
Private Const WM_MOVING As Integer = &H216
Private Const WS_EX_NOACTIVATE As Integer = &H8000000
Protected Overrides ReadOnly Property CreateParams() As System.Windows.Forms.CreateParams
Get
Dim cp As CreateParams = MyBase.CreateParams
cp.ExStyle = cp.ExStyle Or WS_EX_NOACTIVATE
Return cp
End Get
End Property
Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
If m.Msg = WM_MOVING Then
Dim r As RECT = DirectCast(Runtime.InteropServices.Marshal.PtrToStructure(m.LParam, GetType(RECT)), RECT)
Me.Location = New Point(r.Left, r.Top)
End If
MyBase.WndProc(m)
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Console.WriteLine("...your active screen capture code here...")
End Sub
End Class