Send message to a Windows process (not its main window)

Question

I have an application that on a subsequent start detects if there\'s a process with the same name already running and, if so, activates the running app\'s window and then ex

Answer 1

Named Pipes can be used for this. It might be the more acceptable method with .net.You can define a service in the main application that accepts a message from the calling application. Here's a sample of the service, in vb. It calls the main app and passes a string to it, in this case, a filename. It also returns a string, but any parameters can be used here.

Public Class PicLoadService : Implements IMainAppPicLoad

Public Function LoadPic(ByVal fName As String) As String Implements IMainAppPicLoad.LoadPic
' do some stuff here.
LoadPic = "return string"
End Function

End Class

The setup in the calling application is a little more involved. The calling and main application can be the same application.

Imports System.Diagnostics
Imports System.ServiceModel
Imports System.IO
Imports vb = Microsoft.VisualBasic

Module MainAppLoader

Sub Main()

Dim epAddress As EndpointAddress
Dim Client As picClient
Dim s As String
Dim loadFile As String
Dim procs() As Process
Dim processName As String = "MainApp"

loadFile = "" ' filename to load

procs = Process.GetProcessesByName(processName)

If UBound(procs) >= 0 Then
  epAddress = New EndpointAddress("net.pipe://localhost/MainAppPicLoad")
  Client = New picClient(New NetNamedPipeBinding, epAddress)
  s = Client.LoadPic(loadFile)
End If

End Sub

 _
Partial Public Class picClient
    Inherits System.ServiceModel.ClientBase(Of IMainAppPicLoad)
    Implements IMainAppPicLoad

    Public Sub New(ByVal binding As System.ServiceModel.Channels.Binding, ByVal remoteAddress As System.ServiceModel.EndpointAddress)
        MyBase.New(binding, remoteAddress)
    End Sub

    Public Function LoadPic(ByVal fName As String) As String Implements IMainAppPicLoad.LoadPic
        Return MyBase.Channel.LoadPic(fName)
    End Function

End Class

' from here down was auto generated by svcutil.
' svcutil.exe /language:vb /out:generatedProxy.vb /config:app.config http://localhost:8000/MainAppPicLoad
' Some has been simplified after auto code generation.
 _
Public Interface IMainAppPicLoad
   _
  Function LoadPic(ByVal fName As String) As String
End Interface

 _
Public Interface IMainAppPicLoadChannel
  Inherits IMainAppPicLoad, System.ServiceModel.IClientChannel
End Interface

 _
Partial Public Class IMainAppPicLoadClient
  Inherits System.ServiceModel.ClientBase(Of IMainAppPicLoad)
  Implements IMainAppPicLoad

  Public Sub New(ByVal binding As System.ServiceModel.Channels.Binding, ByVal remoteAddress As System.ServiceModel.EndpointAddress)
    MyBase.New(binding, remoteAddress)
  End Sub

  Public Function LoadPic(ByVal fName As String) As String Implements IMainAppPicLoad.LoadPic
    Return MyBase.Channel.LoadPic(fName)
  End Function
End Class

End Module

 Public Interface IMainAppPicLoad
 Function LoadPic(ByVal fName As String) As String
End Interface