vb.net – WinForms应用程序之间的SendMessage – 表单需要关注

我正在使用 Windows Messages API在两个Windows窗体应用程序之间进行通信.我拿出了一个表单,该表单是应用程序的一部分,并将其放入自己的应用程序中,以便在加载时,用户仍然可以在一个单独的应用程序中处理其他表单.

我需要能够在两个应用程序之间进行通信,以便现在单独的应用程序表单可以告诉主应用程序打开什么.

我在主应用程序的主窗体上使用此代码,它工作得很好…除非主窗体没有焦点.

Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
    Try
        Select Case m.Msg
            Case &H400
                BS.BuildString(m.LParam)
            Case Else
                MyBase.WndProc(m)
        End Select
    Catch ex As Exception

    End Try
End Sub

我之前从未使用过Windows Message API,我只是通过查找表单之间的通信来抓住这个,所以我是新手.通过做更多研究我知道的是我需要一个仅消息窗口来处理消息.我不明白该怎么做.
我看了一些像this one这样的文章和解决方案,我认为我遇到的问题是我不知道如何实现它.

编辑1

以下是第二个应用程序查找和发送到主应用程序的方式.

'used to send a message using SendMessage API to the 
                'main app to open the ID
                Private WithEvents BS As New BuildString 
                'get this running process
                Dim proc As Process = Process.GetCurrentProcess()
                'get all other (possible) running instances
                Dim processes As Process() = Process.GetProcessesByName("ProcessName")

                If processes.Length > 0 Then
                    'iterate through all running target applications
                    For Each p As Process In processes
                        'now send the ID to the running instance of the main app
                        BS.PostString(p.MainWindowHandle, &H400, 0, "ID:" & ID)
                    Next
                Else
                    MessageBox.Show("Main application not running")
                End If

这是两个应用程序中BuildString的类.

Imports System.Text

Public Class BuildString

Private Declare Function PostMessage Lib "user32.dll" Alias "PostMessageA" (ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
Public Event StringOK(ByVal Result As String)
Private hwnd As Integer = 0
Private wMsg As Integer = 0
Private wParam As Integer = 0
Private lParam As String = ""
Private tempA(-1) As Byte
Private enc As Encoding = Encoding.UTF8

Public Property Encode() As Encoding
    Get
        Return enc
    End Get
    Set(ByVal value As Encoding)
        enc = value
    End Set
End Property

Public Sub BuildString(ByVal b As IntPtr)
    If b <> 0 Then
        'build temp array
        Dim tempB(tempA.Length) As Byte
        tempA.CopyTo(tempB, 0)
        tempB(tempA.Length) = b
        ReDim tempA(tempB.Length - 1)
        tempB.CopyTo(tempA, 0)
    Else
        'decode byte array to string
        Dim s As String
        If enc Is Encoding.UTF8 Then
            s = Encoding.UTF8.GetString(tempA)
        ElseIf enc Is Encoding.Unicode Then
            s = Encoding.Unicode.GetString(tempA)
        ElseIf enc Is Encoding.ASCII Then
            s = Encoding.ASCII.GetString(tempA)
        Else
            s = Encoding.Default.GetString(tempA)
        End If
        'send out result string via event
        RaiseEvent StringOK(s)
        ReDim tempA(-1)
    End If
End Sub

Public Sub PostString(ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, ByVal lParam As String)
    Me.hwnd = hwnd
    Me.wMsg = wMsg
    Me.wParam = wParam
    Me.lParam = lParam
    'create a new thread to post window message
    Dim t As Threading.Thread
    t = New Threading.Thread(AddressOf SendString)
    t.Start()
End Sub

Private Sub SendString()
    'create byte array
    Dim ba() As Byte
    'encode string to byte array
    If enc Is Encoding.UTF8 Then
        ba = Encoding.UTF8.GetBytes(lParam)
    ElseIf enc Is Encoding.Unicode Then
        ba = Encoding.Unicode.GetBytes(lParam)
    ElseIf enc Is Encoding.ASCII Then
        ba = Encoding.ASCII.GetBytes(lParam)
    Else
        ba = Encoding.Default.GetBytes(lParam)
    End If
    Dim i As Integer
    For i = 0 To ba.Length - 1
        'start post message
        PostMessage(hwnd, wMsg, wParam, ba(i))
    Next
    'post a terminator message to destination window
    PostMessage(hwnd, wMsg, wParam, 0)
End Sub

结束班

以下是在解码消息后运行的主应用程序上的代码.

Private Sub SB_StringOK(ByVal Result As String) Handles BS.StringOK
    Dim sArray() As String = Result.Split(";")
    'rest of the code to open the ID
End Sub

感谢@JustinRyan我用 FindWindow想出来了.

我将此添加到我发送消息的第二个应用程序中.

Private Declare Function FindWindow1 Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Integer

我没有找到应用程序进程,而是找到了我想要的窗口,并在发送消息中将其直接发送给它.

Dim parenthwnd As Integer = FindWindow1(Nothing, "Form Name")
BS.PostString(parenthwnd, &H400, 0, "ID:" & ID)

它就像我需要的那样工作.

由于答案在评论中,我不确定如何显示正确的答案.请让我知道在这种情况下的正确礼仪,以给予用户应有的信誉.