VB.NET Express2005 ACADv05

I wrote a test .exe which fires ADT05 then draws a line and
a circle..zooms..ect.

Code fires from a button and works fine; only I was having a problem with
ADT firing multiple times(two or three) after clicking the button, but
before my code even got to execute the buttons click event.[which is the
only section of code which fires ACAD].

Object were not created in those versions. Finally click event would execute
creating another version with all objects drawn as expected.

I found the problem to be in this line:
acadApp = GetObject(, "AutoCAD.Application")'correct

Which I had accidently typed as: ("" added)
acadApp = GetObject("", "AutoCAD.Application")'wrong

Once "" were removed problem was solved. Could someone please explain what
was happening? Attached segment below; which works fine..

TFYT..
Paul
Private Sub Command1_Click(ByVal eventSender As System.Object, _

ByVal eventArgs As System.EventArgs) Handles Command1.Click

On Error Resume Next

' Connect to the AutoCAD application

Dim acadApp As Autodesk.AutoCAD.Interop.AcadApplication

acadApp = GetObject(, "AutoCAD.Application")

If Err.Number Then

Err.Clear()

acadApp = CreateObject("AutoCAD.Application")

If Err.Number Then

MsgBox(Err.Description)

Exit Sub

End If

End If

 

Paul,

When using the GetObject and CreateObject methods your telling your app that your going to use a reference to an ActiveX object. Your either going to supply the pathname or class for the object.

"" was saying, obtain a reference to this object from this ("") pathname. Since "" wasn't something like C:\Program Files\CAD\ACAD.exe nothing happened for you. Once you added the second optional parameter (AutoCAD.Application) your app knew what to do.

It went to \HKEY_LOCAL_MACHINE\Software\CLASSES\AutoCAD.Application hive and looked at the CLSID to see what object was going to be started. CLSID revealed that the object being referenced could be 8E75D11-3D21-11d2-85C4-080009A0C626, thus start me now.

Hope this helps,

Bob Coward
CADS, Inc

800-366-0946

 

Nice explanation Bob, Thank You...

that your going to use a reference to an ActiveX object. Your either going
to supply the pathname or class for the object.

Since "" wasn't something like C:\Program Files\CAD\ACAD.exe nothing
happened for you. Once you added the second optional parameter
(AutoCAD.Application) your app knew what to do.

and looked at the CLSID to see what object was going to be started. CLSID
revealed that the object being referenced could be
8E75D11-3D21-11d2-85C4-080009A0C626, thus start me now.

 

The hardest part about .NET is breaking old habits. In it, you have no need
to use CreateObject or GetObject and shouldn't use them:

Public Function Connect2ACAD() As Integer
Try
'get existing
cadApp = GetActiveObject("AutoCAD.Application")
Return 1
Catch
'no existing so try to create
Try
cadApp = New AcadApplication
Return 2
Catch
'no AutoCAD found
Return 0
End Try
End Try
End Function

This function creates or retrieves a session of AutoCAD and reports back
whether it started it or not:

0 = no AutoCAD found
1 = current instance
2 = started instance

-- Mike
___________________________
Mike Tuersley
CADalyst's CAD Clinic
Rand IMAGINiT Technologies
___________________________
the trick is to realize that there is no spoon...

 

Thanks Mike, I was hoping someone would comment on the code...

 

Mike,

I'd like to talk about an issue of style. Do your often use return codes
like this?

I avoid them. At the very least, where a value represents some form of
enumeration, I create an enum for that purpose.

However, in a situation like this I always opt to throw an exception
with a descriptive message.

 

Hi Frank,

Well, often is a relative term =) In the half dozen or so projects I've
done in .NET, yes, I've used them exclusively.

I typically start Enums after 3 values. To me, anything less than 4 isn't
worth the effort or should I say I don't see the value. I could be
completely off base here, I'll admit that.

Throw an exception to whom? A user or your calling app? I should mention
that usually my apps don't involve users - especially the .NET ones. They
are all automated "configurators" where the user enters data somewhere else
and I receive notification from a web method, dbase entry, a dropped file
in a watched directory, or passed as a parameter. My program then runs and
passes back a return value that indicates success or failure as well as
kicking information into a log file of some type. If I was creating a
userinterface program, then I concur and would do as you suggest.

In this particular case, the only reason I distinguish between Create and
Get is so I know whether to shutdown AutoCAD or not. I actually raise an
event error with the calling app that this snippet came from - which I
stripped before posting because it would've confused things I thought.

On the whole, I have read quite a few articles on using the Return as part
of C# and VB.NET [all non-AutoCAD specific articles] and decided to make
the habit of doing it that way. I'm far from a .NET expert so there may be
underlying issues that I haven't stumbled across yet but this method seemed
to make sense to me. So far I haven't had any problems with it either --->
unless its the root of that weird dbase issue I had?! I'm open for any
critiques or opinions on how best to incorporate .NET and Adesk stuff.

-- Mike
___________________________
Mike Tuersley
CADalyst's CAD Clinic
Rand IMAGINiT Technologies
___________________________
the trick is to realize that there is no spoon...

 

I use enums simply for their declarative value. It avoids having to look
through source or documentation to discover the meaning of a numeric value.

For example: AutoCADSession.SessionCreated is a whole lot more readable
than 2.

When you're talking about numeric input from calling apps, there's just
no other way to go as enums restrict the callers to valid input.

The caller, of course. The caller can then choose how to deal with the
problem. Not finding AutoCAD on the system is definitely an exceptional
situation for an AutoCAD add-in so the behavior is quite appropriate in
the instance you illustrated.

I wrote a handly little class once that automatically connects to
AutoCAD and uses an internal member to track whether it connected to or
created an AutoCAD instance.

That allowed the class to respond appropriately when its Dispose method
was called. I'll see if I can dig it up.

That's just too Win32 API for my taste. But as I mentioned earlier, it's
just a matter of taste so it's not like there's any compelling reason
to do things differently if your current practices serve you well.

 

Here it is:

http://server73.totalchoicehosting.com/~acadxfo/dotnet/001.htm

The information dates back to AutoCAD 2000 but it ports just fine.

 

Thanks Frank! I'm looking forward to reading it =)
-- Mike
___________________________
Mike Tuersley
CADalyst's CAD Clinic
Rand IMAGINiT Technologies
___________________________
the trick is to realize that there is no spoon...

 

When you're talking about numeric input from calling apps, there's just

Hmmmmmm..........I hadn't "looked" at it that way before only from the "got
to code it" viewpoint. I'll have to reconsider my approach.

How do you normally choose to handle it? Send back a value the conventional
way and continue with the func terminating, etc. as you go? I was under the
impression that the Return better handled clearing out vars and was some
how associated with garbage collection. I'm very interested - you already
turned me on the Enums =)

-- Mike
___________________________
Mike Tuersley
CADalyst's CAD Clinic
Rand IMAGINiT Technologies
___________________________
the trick is to realize that there is no spoon...

 

Enums are great for this as well as bit-coded values.

I've been doing so many classes that I normally implement some kind of
LastError property for non-exceptional errors. The few times that I do
return a value as a status indicator, I'll go with an enum (like the
DialogResult return value from ShowDialog).

 

Very nice article but I can't get it to print correctly from either Firefox
or IE. It keeps cutting off the right side. Any ideas?

~Tim Riley

 

I guess I could do that but it seems strange that it won't print correctly
from a web browser. Thanks.

~Tim Riley