FindWindowEx

FindWindowEx retrieves the handle to a window whose class name and/or window name match the specified strings. The function searches child windows, beginning with the one following the given child window.

Code:

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    Const HWND_DESKTOP As Int32 = 0
    Public Declare Function apiFindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Int32, ByVal hWnd2 As Int32, ByVal lpsz1 As String, ByVal lpsz2 As String) As Int32

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Me.Text = "Form1"

        'Get handle by window title.  You can specify the class name too.
        Dim hwnd As Int32 = apiFindWindowEx(HWND_DESKTOP, 0, Nothing, "Form1")
        Me.Text = "Handle by title: " & hwnd
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Me.Text = "Form1"

        'Get handle by window class name.
        Dim hwnd As Int32 = apiFindWindowEx(HWND_DESKTOP, 0, "WindowsForms10.Window.8.app.0.378734a", Nothing)
        Me.Text = "Handle by class name: " & hwnd
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Me.Text = "Form1"

        'Get handles of all sibling windows that have the same parent(Desktop window).
        Dim hwnd As Int32 = HWND_DESKTOP
        Dim cwnd As Int32 = 0
        Do
            cwnd = apiFindWindowEx(hwnd, cwnd, Nothing, Nothing)
            If cwnd = 0 Then Exit Do
            Me.Text = "Top level sibling handle: " & cwnd
            System.Threading.Thread.Sleep(1) 'Give a chance to see the new handle
        Loop
    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        Me.Text = "Form1"

        ' Get child window by window title.  You can specify the class name too.
        Dim hwnd As Int32 = apiFindWindowEx(HWND_DESKTOP, 0, Nothing, "Form1")
        Dim cwnd As Int32 = apiFindWindowEx(hwnd, 0, Nothing, "Button1")
        Me.Text = "Child handle by title: " & cwnd
    End Sub

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Me.Text = "Form1"

        'Get handle of all sibling child windows that have the same parent(Top-level window).
        Dim hwnd As Int32 = apiFindWindowEx(HWND_DESKTOP, 0, Nothing, "Form1")
        Dim cwnd As Int32 = 0
        Do
            cwnd = apiFindWindowEx(hwnd, cwnd, Nothing, Nothing)
            If cwnd = 0 Then Exit Do
            Me.Text = "Child sibling handle: " & cwnd
            System.Threading.Thread.Sleep(200) 'Give a chance to see the new handle.
        Loop
    End Sub

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