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[M1z23R]

How could you auto choose webcam device, or auto respond to this dialog ?

[mandai]

I have found there are a few ways to discover/communicate with this window.

If you just want to detect the window and automatically click the OK button you could use this:

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    <DllImport("user32.dll")> Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As UInteger, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr
    End Function

    <DllImport("user32.dll")> Shared Function FindWindow(ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr
    End Function

    <DllImport("user32.dll")> Shared Function FindWindowEx(ByVal hwndParent As IntPtr, ByVal hwndChildAfter As IntPtr, ByVal lpszClass As String, ByVal lpszWindow As String) As IntPtr
    End Function

    Const BM_CLICK As UInteger = &HF5

    Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles Timer1.Tick

        Dim dialog As IntPtr = FindWindow(Nothing, "Video Source")

        If dialog <> IntPtr.Zero Then

            Timer1.Stop()

            Dim btnOk As IntPtr = FindWindowEx(dialog, IntPtr.Zero, Nothing, "OK")
            SendMessage(btnOk, BM_CLICK, IntPtr.Zero, IntPtr.Zero)

        End If
    End Sub

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

        Timer1.Interval = 100
        Timer1.Enabled = True
    End Sub

If you want to get the item count and set the ComboBox index you could use something like this:

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    Const CB_GETCOUNT As UInteger = &H146
    Const CB_SETCURSEL As UInteger = &H14E

...

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            Dim tabPage As IntPtr = FindWindowEx(dialog, IntPtr.Zero, Nothing, "Capture Source")

            Dim comboBox As IntPtr = FindWindowEx(tabPage, IntPtr.Zero, "ComboBox", Nothing)

            'get the number of devices
            Dim deviceCount As IntPtr = SendMessage(comboBox, CB_GETCOUNT, IntPtr.Zero, IntPtr.Zero)
            MsgBox(deviceCount)

            'set the device index
            Dim newindex As Integer = -1 'this would invalidate the current index
            Dim ptrNewindex As IntPtr = New IntPtr(newindex)
            SendMessage(comboBox, CB_SETCURSEL, ptrNewindex, IntPtr.Zero)