VB.NET Windows API Example

Imports System.Runtime.InteropServices

Public Class Form1
    'SendMessage API Declaration:

    Private Declare Auto Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal msg As Integer, ByVal wParam As IntPtr, ByVal lParam As String) As IntPtr
    Private Declare Function ShowWindow Lib "user32.dll" (ByVal hwnd As IntPtr, ByVal nCmdShow As IntPtr) As IntPtr
    'FindWindowEx API Declaration:

    Private Const WM_GETTEXT As Integer = &HD


    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function FindWindowEx(ByVal parentHandle As IntPtr, _
                      ByVal childAfter As IntPtr, _
                      ByVal lclassName As String, _
                      ByVal windowTitle As String) As IntPtr
    End Function

    'FindWindow API Declaration:

    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function FindWindow( _
     ByVal lpClassName As String, _
     ByVal lpWindowName As String) As IntPtr
    End Function

    Const WM_SETTEXT As Long = &HC 'WM_SETTEXT Constant. For setting text to objects in Windows applications.
    Const WS_MINIMIZE As Integer = &H20000000
    Const WM_CLOSE = &H10 'WM_CLOSE Constant. For closing any open Windows applications.
    Private Declare Function GetWindowPlacement Lib "user32" (ByVal hwnd As IntPtr, ByRef lpwndpl As WINDOWPLACEMENT) As Integer

    Private Structure POINTAPI
        Public x As Integer
        Public y As Integer
    End Structure

    Private Structure RECT
        Public Left As Integer
        Public Top As Integer
        Public Right As Integer
        Public Bottom As Integer
    End Structure

    Private Structure WINDOWPLACEMENT
        Public Length As Integer
        Public flags As Integer
        Public showCmd As Integer
        Public ptMinPosition As POINTAPI
        Public ptMaxPosition As POINTAPI
        Public rcNormalPosition As RECT
    End Structure

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim intRet As Integer
        Dim wpTemp As WINDOWPLACEMENT

        Dim lpszParentClass As String = "MozillaWindowClass" 'The name of the Calc.exe parent class.
        'IEFrame 'MozillaWindowClass
        Dim lpszParentWindow As String = "Google - Mozilla Firefox" 'The title of the Calc.exe window.
        'MSN.com - Windows Internet Explorer 'Google - Mozilla Firefox
        Dim ParenthWnd As New IntPtr(0) 'New IntPtr variable.

        Dim hWnd As New IntPtr(0) 'New IntPtr variable.

        ParenthWnd = FindWindow(lpszParentClass, lpszParentWindow)

        wpTemp.Length = System.Runtime.InteropServices.Marshal.SizeOf(wpTemp)
        intRet = GetWindowPlacement(Me.Handle.ToInt32, wpTemp)
        'Me.Handle.ToInt32
        If wpTemp.showCmd = 1 Then
            ' ActiveForm.WindowState = FormWindowState.Minimized
        ElseIf wpTemp.showCmd = 2 Then
            ' ActiveForm.WindowState = FormWindowState.Maximized
        ElseIf wpTemp.showCmd = 3 Then
            '  ActiveForm.WindowState = FormWindowState.Normal
        End If

        If Not ParenthWnd = (IntPtr.Zero) Then 'Make sure we can find Calc.exe.
            'Dim NumText As New IntPtr
            'NumText = SendMessage(ParenthWnd, WM_GETTEXT, 24, 0)
            'Dim Text As String = (NumText)

            'Display the string using a label
            'MessageBox.Show(Text)
            'SendMessage(ParenthWnd, WM_SETTEXT, 5, "yo sup")
            ShowWindow(ParenthWnd, 3)
            'System.Threading.Thread.Sleep(50000)
            'SendMessage(ParenthWnd, &H10, 0, 0) '&H10=WM_CLOSE
            'SendMessage(ParenthWnd, WM_CLOSE, 0, 0)

        Else

            MessageBox.Show("Application Not Running!!", "Firefox Win API Source Code", MessageBoxButtons.OK, MessageBoxIcon.Error)

            Exit Sub

        End If

    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim intRet As Integer
        Dim wpTemp As WINDOWPLACEMENT

        Dim lpszParentClass As String = "MozillaWindowClass" 'The name of the Calc.exe parent class.
        'IEFrame 'MozillaWindowClass
        Dim lpszParentWindow As String = "Google - Mozilla Firefox" 'The title of the Calc.exe window.
        'MSN.com - Windows Internet Explorer 'Google - Mozilla Firefox
        Dim ParenthWnd As New IntPtr(0) 'New IntPtr variable.

        Dim hWnd As New IntPtr(0) 'New IntPtr variable.

        ParenthWnd = FindWindow(lpszParentClass, lpszParentWindow)

        wpTemp.Length = System.Runtime.InteropServices.Marshal.SizeOf(wpTemp)
        intRet = GetWindowPlacement(Me.Handle.ToInt32, wpTemp)
        'Me.Handle.ToInt32
        If wpTemp.showCmd = 1 Then
            ' ActiveForm.WindowState = FormWindowState.Minimized
        ElseIf wpTemp.showCmd = 2 Then
            ' ActiveForm.WindowState = FormWindowState.Maximized
        ElseIf wpTemp.showCmd = 3 Then
            '  ActiveForm.WindowState = FormWindowState.Normal
        End If

        If Not ParenthWnd = (IntPtr.Zero) Then 'Make sure we can find Calc.exe.

            'SendMessage(ParenthWnd, WM_SETTEXT, 5, "yo sup")

            'System.Threading.Thread.Sleep(50000)

            'SendMessage(ParenthWnd, WM_CLOSE, 0, 0)

            ShowWindow(ParenthWnd, 2)

        Else

            MessageBox.Show("Application Not Running!!", "Firefox Win API Source Code", MessageBoxButtons.OK, MessageBoxIcon.Error)

            Exit Sub

        End If
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim intRet As Integer
        Dim wpTemp As WINDOWPLACEMENT

        Dim lpszParentClass As String = "MozillaWindowClass" 'The name of the Calc.exe parent class.
        'IEFrame 'MozillaWindowClass
        Dim lpszParentWindow As String = "Google - Mozilla Firefox" 'The title of the Calc.exe window.
        'MSN.com - Windows Internet Explorer 'Google - Mozilla Firefox
        Dim ParenthWnd As New IntPtr(0) 'New IntPtr variable.

        Dim hWnd As New IntPtr(0) 'New IntPtr variable.

        ParenthWnd = FindWindow(lpszParentClass, lpszParentWindow)

        wpTemp.Length = System.Runtime.InteropServices.Marshal.SizeOf(wpTemp)
        intRet = GetWindowPlacement(Me.Handle.ToInt32, wpTemp)
        'Me.Handle.ToInt32
        If wpTemp.showCmd = 1 Then
            ' ActiveForm.WindowState = FormWindowState.Minimized
        ElseIf wpTemp.showCmd = 2 Then
            ' ActiveForm.WindowState = FormWindowState.Maximized
        ElseIf wpTemp.showCmd = 3 Then
            '  ActiveForm.WindowState = FormWindowState.Normal
        End If

        If Not ParenthWnd = (IntPtr.Zero) Then 'Make sure we can find Calc.exe.

            'SendMessage(ParenthWnd, WM_SETTEXT, 5, "yo sup")

            'System.Threading.Thread.Sleep(50000)

            SendMessage(ParenthWnd, WM_CLOSE, 0, 0)

            'ShowWindow(ParenthWnd, 2)

        Else

            MessageBox.Show("Application Not Running!!", "Firefox Win API Source Code", MessageBoxButtons.OK, MessageBoxIcon.Error)

            Exit Sub

        End If
    End Sub
End Class