PRB: VB5.0 OLE Automation Error --2147418107 (80010005)
ID: Q176399
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The information in this article applies to:
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Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0
SYMPTOMS
When a compiled Visual Basic application makes calls to an ActiveX
server via a timer event, the following error may occur:
Run-time error '-2147418107 (80010005)': Automation error
CAUSE
After the first WM_TIMER event is fired, subsequent WM_TIMER events cannot
be processed until the first event is completed. The error message equates
to:
It is illegal to call out while inside message filter.
RESOLUTION
Three workarounds have been implemented with success:
Workaround 1
Set a boolean flag in the timer event (see code listed in the Steps to
Reproduce Behavior section below).
- Select Project .Add Module and add a standard module
- Type the following code into the module:
Public flag As Boolean
- Change the Timer1_Timer event code to read as follows:
Private Sub Timer1_Timer()
If Not flag Then
flag = True
RetStr = t.Test(100000)
flag = False
End If
Text1.Text = RetStr
End Sub
By doing this, the timer can't call the server until the previous call is
completed.
Workaround 2
Create the server as a DLL, not an EXE. ActiveX DLLs are in-process
servers. An in-process server would not use Remote Procedure Call engine
(RPC). (See the MORE INFORMATION below.)
Workaround 3
Place error handling in effect to ignore the error:
Private Sub Timer1_Timer()
On Error Resume Next
RetStr = t.Test(100000)
End Sub
STATUS
This behavior is by design.
MORE INFORMATION
Timers in Microsoft Windows are fired by Windows placing WM_TIMER messages
in a windows message queue. For example, an application receives the first
timer's WM_TIMER message in its window proc. This causes Visual Basic to
fire the first timer's Timer event, which calls the ActiveX server through
the Remote Procedure Call engine (RPC) because ActiveX EXE servers run in a
separate process.
While the Visual Basic application is waiting for the RPC call to complete,
the RPC engine allows the Visual Basic application to sit and poll its
message queue. This is allowed primarily for screen redraw (if WM_PAINT
messages come in because the user was switching around windows), so the
application can update its windows while it is waiting for the RPC call to
complete.
If, while Visual Basic waits for the first RPC call to complete, it
processes a second WM_TIMER message coming in through the RPC message
filter, this causes Visual Basic to fire the second timer's Timer event,
which attempts to call the ActiveX server again through the RPC engine.
However, the RPC engine explicitly does not allow an application to make an
RPC call when it is in the RPC message filter, so it returns an error that
Visual Basic returns to the user.
At the point at which Visual Basic gets the WM_TIMER message, there is no
way for Visual Basic to know whether firing the Timer event will cause an
RPC call to be made. In fact, because ActiveX servers can be transparently
remote, there is no way for Visual Basic to know, when it is calling an
object method, whether that method will be routed through the RPC engine.
Thus, there is no way for Visual Basic to know ahead of time that the RPC
engine is going to throw an error.
Steps to Reproduce Behavior
NOTE: The error will not reproduce unless you have compiled the projects.
Server
- Start a new ActiveX EXE project.
- Change the following properties:
Project Name:TestDelayServer
Class Name: cTestClass
- Place the following code into cTestClass:
Option Explicit
Public Function Test(Optional delay As Long = 1000) as String
Dim index As Long
Dim Y As String
Dim X As String
Y = "a;lskdjf;laksdjf;lkasjd;flkajsmd;lfkjma;sldkfj;laskdj"
For index = 1 To delay
X = Right(Y, CInt(Len(Y) / 2))
X = ""
Next
Test = "I'm here"
End Function
- Compile the EXE.
- Run the EXE to register it.
Client
- Start a new Standard EXE.
- Select TestDelayServer from the Project - References menu.
- Insert a Command Button, Timer Control and TextBox Control.
- Place the following code into Form1's code window:
Option Explicit
Dim t As New TestDelayServer.cTestClass
Dim f As Form
Public RetStr As String
Private Sub Command1_Click()
Set f = New Form1
f.Show
End Sub
Private Sub Form_Load()
Timer1.Interval = 1000
Timer1.Enabled = True
End Sub
Private Sub Timer1_Timer()
RetStr = t.Test(100000)
Text1.Text = RetStr
End Sub
- Save the project.
- Compile the EXE.
- Run the compiled EXE. Note that the Automation error occurs.
Keywords : kberrmsg kbole kbVBp500 kbVBp600 kbGrpVB
Version :
Platform :
Issue type : kbprb