Option Strict Off
Option Explicit On
Friend Class Form1
	Inherits System.Windows.Forms.Form
    Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal _
      lpClassName As String, ByVal lpWindowName As String) As Integer
    Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
    ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, _
    ByRef lParam As Integer) As Integer
 
    Const WM_COPYDATA As Integer = &H4AS
 
    Private Sub Command3_Click(ByVal eventSender As System.Object, ByVal _
      eventArgs As System.EventArgs) Handles Command3.Click
        Call SendData()
    End Sub
 
    Private Function SendData() As Boolean
        Dim DesthWnd As Integer
 
        DesthWnd = FindWindow(vbNullString, "Destination")
        If DesthWnd = 0 Then
            MsgBox("Das Zielfenster wurde nicht gefunden" & vbCrLf & "Bitte" & _
              "Starten sie erst das andere Projekt!")
        Else
            Call SendMessage(DesthWnd, WM_COPYDATA, Me.Handle.ToInt32, 3)
        End If
    End Function
End Class

Option Strict Off
Option Explicit On 
Friend Class Form2
    Inherits System.Windows.Forms.Form
 
    Private Declare Function CallWindowProc Lib "user32" Alias _
      "CallWindowProcA" (ByVal lpPrevWndFunc As Integer, ByVal hWnd As Integer, _
      ByVal Msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) _
      As Integer
    Private Delegate Function SubClassProcDelegate(ByVal hwnd As Integer, ByVal _
    msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
    Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" ( _
    ByVal hWnd As Integer, ByVal nIndex As Integer, ByVal lVal As _
    SubClassProcDelegate) As Integer
    Const GWL_WNDPROC As Integer = -4
    Const WM_COPYDATA As Integer = &H4AS
 
    Dim PrevWndProc As Integer
    Dim s As Integer
 
    Private Sub Form2_Load(ByVal eventSender As System.Object, ByVal eventArgs _
      As System.EventArgs) Handles MyBase.Load
        Call Init(Me.Handle.ToInt32)
    End Sub
    Public Sub Color_Change()
        If Me.Text1.BackColor.ToString = "Color [Red]" Then Me.Text1.BackColor _
          = System.Drawing.Color.White Else Me.Text1.BackColor = _
          System.Drawing.Color.Red
    End Sub
    Private Function WindowProc(ByVal hWnd As Integer, ByVal Msg As Integer, _
      ByVal wParam As Integer, ByVal lParam As Integer) As Integer
        If Msg = WM_COPYDATA Then
            Call Color_Change()
        End If
        WindowProc = CallWindowProc(PrevWndProc, hWnd, Msg, wParam, lParam)
    End Function
    Public Sub Init(ByRef hWnd As Integer)
        'UPGRADE_WARNING: Einen Delegaten für AddressOf WindowProc hinzufügen 
        ' Klicken Sie hier für weitere Informationen: 
        ' 'ms-help://MS.VSCC/commoner/redir/redirect.htm?keyword="vbup1048"'
        If PrevWndProc = 0 Then
            PrevWndProc = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf WindowProc)
        End If
    End Sub
End Class