How to make SendKeys act Synchronously in IBM Host

I use the IBM Host Access Class Library for COM Automation as a way to communicate with an IBM AS400 (aka iSeries, IBM i, green screen, 5250) through a terminal emulator. I notice that when you issue a "SendKeys" instruction, control returns to your application before the IBM emulator finishes with the command. This can lead to timing problems because you might then send another "SendKeys" instruction before the system is ready to accept it.

For example:

Imports AutPSTypeLibrary
Imports AutConnListTypeLibrary
Imports AutSessTypeLibrary

Sub Example
    Dim connections As New AutConnList
    connections.Refresh()
    If connections.Count < 1 Then Throw New InvalidOperationException("No AS400 screen can currently be found.")
    Dim connection As IAutConnInfo = DirectCast(connections(1), IAutConnInfo)

    _Session = New AutSess2
    _Session.SetConnectionByHandle(connection.Handle)
    Dim _Presentation As AutPS = DirectCast(_Session.autECLPS, AutPS)
    _Presentation.SendKeys("PM70[enter]", 22, 8)
    _Presentation.SendKeys("ND71221AD[enter]", 22, 20)

End Sub

would work correctly when stepping through code in a debugger, but would fail when running normally because the second instruction was sent too soon.

One way to work with this is to put a timer or loop after each command to slow the calling program down. I consider this less than ideal because the length of time is not always predictable, you will often be waiting longer than necessary to accommodate an occasional hiccup. This slows down the run time of the entire process.

Another way to work around this is to wait until there is a testable condition on the screen as a result of your sent command. This will work sometimes, but some commands do not cause a screen change to test and if you are looking to abstract your command calling into a class or subroutine, you would have to pass in what screen condition to be watching for.

What I would like to find is one of the "Wait" methods that will work in the general case. Options like the autECLScreenDesc class seem like they have to be tailored to very specific conditions.

The autECLPS (aka AutPS) class has a number of Wait methods (Wait, WaitForCursor, WaitWhileCursor, WaitForString, WaitWhileString, WaitForStringInRect, WaitWhileStringInRect, WaitForAttrib, WaitWhileAttrib, WaitForScreen, WaitWhileScreen) but they also seem to be waiting for specific conditions and do not work for the general case. The general case it important to me because I am actually trying to write a general purpose field update subroutine that can be called from many places inside and outside of my .dll.

This example is written in VB.NET, but I would expect the same behavior from C#, C++, VB6, Java; really anything that uses IBM's Personal Communications for Windows, Version 6.0 Host Access Class Library.

The "Operator Information Area" class seems to provide a solution for this problem.

My general case seems to be working correctly with this implementation:

 Friend Sub PutTextWithEnter(ByVal field As FieldDefinition, ByVal value As String)
    If IsNothing(field) Then Throw New ArgumentNullException("field")
    If IsNothing(value) Then Throw New ArgumentNullException("value")
    _Presentation.SendKeys(Mid(value.Trim, 1, field.Length).PadRight(field.Length) & "[enter]", field.Row, field.Column)
    WaitForEmulator(_Session.Handle)
End Sub

Private Sub WaitForEmulator(ByVal EmulatorHandle As Integer)
    Dim Oia As New AutOIATypeLibrary.AutOIA
    Oia.SetConnectionByHandle(EmulatorHandle)
    Oia.WaitForInputReady()
    Oia.WaitForAppAvailable()
End Sub

I give thanks to a user named "khieyzer" on this message board for pointing our this clean and general-purpose solution.

Edit:

After a few weeks debugging and working through timing and resource release issues, this method now reads like:

Private Sub WaitForEmulator(ByRef NeededReset As Boolean)
    Dim Oia As New AutOIA
    Oia.SetConnectionByHandle(_Presentation.Handle)

    Dim inhibit As InhibitReason = Oia.InputInhibited
    If inhibit = InhibitReason.pcOtherInhibit Then
        _Presentation.SendKeys("[reset]")
        NeededReset = True
        WaitForEmulator(NeededReset)
        Marshal.ReleaseComObject(Oia)
        Exit Sub
    End If

    If Not Oia.WaitForInputReady(6000) Then
        If Oia.InputInhibited = InhibitReason.pcOtherInhibit Then
            _Presentation.SendKeys("[reset]")
            NeededReset = True
            WaitForEmulator(NeededReset)
            Marshal.ReleaseComObject(Oia)
            Exit Sub
        Else
            Marshal.ReleaseComObject(Oia)
            Throw New InvalidOperationException("The system has stopped responding.")
        End If
    End If

    Oia.WaitForInputReady()
    Oia.WaitForAppAvailable()
    Marshal.ReleaseComObject(Oia)
End Sub