Private Sub AttachToWorkerProcess(ByVal appName As String)
    Dim targetPid = FindPoolPIDByName(appName)
    If targetPid = -1 Then
        MessageBox.Show("Unable to find a worker process hosting " + appName)
    End If

    Dim processes As EnvDTE.Processes = DTE.Debugger.LocalProcesses

    For Each proc As EnvDTE.Process In processes
        If proc.ProcessID = targetPid Then
            proc.Attach()
        End If
    Next

End Sub

Private Function FindPoolPIDByName(ByVal appName As String) As Integer
    Dim sm As New Microsoft.Web.Administration.ServerManager()

    Dim appPoolName As String = Nothing
    For Each site In sm.Sites
        For Each app In site.Applications
            If String.Equals(app.Path, "/" & appName, StringComparison.OrdinalIgnoreCase) Then
                appPoolName = app.ApplicationPoolName
            End If
        Next
    Next

    If appPoolName Is Nothing Then
        MessageBox.Show("Unable to find application " & appName)
    End If

    For Each wp In sm.WorkerProcesses
        If wp.AppPoolName = appPoolName Then
            Return wp.ProcessId
        End If
    Next
    Return -1
End Function

Sub AttachToMyApp()
     AttachToWorkerProcess("MyApp")
End Sub