Public Class Form1
 
    Private Declare Function SendMessageByString Lib "user32.dll" Alias _
      "SendMessageA" _
      (ByVal hwnd As IntPtr, _
       ByVal uMsg As Int32, _
       ByVal wParam As IntPtr, _
       ByVal lParam As String) As Integer
 
    Private Const WM_SETTEXT As Int32 = &HC
    Private Const WM_GETTEXT As Int32 = &HD
 
    Private Declare Function SendMessageByInt Lib "user32.dll" Alias _
      "SendMessageA" _
      (ByVal hwnd As IntPtr, _
       ByVal uMsg As Int32, _
       ByVal wParam As Int32, _
       ByVal lParam As Int32) As Integer
 
    Private Const WM_GETTEXTLENGTH As Int32 = &HE
 
    Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
      (ByVal lpClassName As String, _
        ByVal lpWindowName As String) As IntPtr
 
    Private Declare Function FindWindowEx Lib "user32.dll" Alias _
      "FindWindowExA" _
      (ByVal hWnd1 As IntPtr, _
      ByVal hWnd2 As IntPtr, _
      ByVal lpsz1 As String, _
      ByVal lpsz2 As String) As IntPtr
 
    <Runtime.InteropServices.DllImport("user32.dll")> _
        Private Shared Function SendMessage( _
                       ByVal hWnd As IntPtr, _
                       ByVal Msg As Integer, _
                       ByVal wParam As Integer, _
                       ByVal lParam As System.Text.StringBuilder) _
                       As Integer
    End Function
 
    Public Function GetHandle(ByVal ClassName As String) As IntPtr
        Dim hwnd As IntPtr = FindWindow(ClassName, Nothing)
        hwnd = FindWindowEx(hwnd, IntPtr.Zero, "Edit", Nothing)
 
        If (Not hwnd.Equals(IntPtr.Zero)) Then
            Return hwnd
        Else
            Return IntPtr.Zero
        End If
    End Function
 
    Public Sub SetNewText(ByVal hwnd As IntPtr, ByVal txt As String)
        If (Not hwnd.Equals(IntPtr.Zero)) Then
            Call SendMessageByString(hwnd, WM_SETTEXT, IntPtr.Zero, txt)
        End If
    End Sub
 
    Public Function GetNewText(ByVal hwnd As IntPtr) As String
        If (Not hwnd.Equals(IntPtr.Zero)) Then
            Dim SB As New System.Text.StringBuilder
            Dim BufferSize As Integer = 32768
            SB.EnsureCapacity(BufferSize)
 
            SendMessage(hwnd, WM_GETTEXT, BufferSize, SB)
            Return SB.ToString
        Else
            Return ""
        End If
    End Function
 
    Public Function GetTextLength(ByVal hwnd As IntPtr) As Integer
        If (Not hwnd.Equals(IntPtr.Zero)) Then
            Dim Length As Integer = SendMessageByInt(hwnd, WM_GETTEXTLENGTH, 0, _
              0)
            If Length > 0 Then
                Return Length
            Else
                Return 0
            End If
        End If
    End Function
 
    Private Sub Button1Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dim hwnd As IntPtr = GetHandle("Notepad")
        If (Not hwnd.Equals(IntPtr.Zero)) Then
            'Call SetNewText(hwnd, "http://www.visual-basic5.de")
            MsgBox(GetNewText(hwnd))
        Else
            MessageBox.Show("Notepad not found...", "Info")
        End If
 
    End Sub
 
End Class