Through the Interface

Handling COM calls rejected by AutoCAD from an external .NET application

We’ve had a few reports from people implementing external .NET applications to drive AutoCAD – as shown in this previous post – experiencing intermittent failures once AutoCAD 2010 Update 1 has been applied. Here’s a typical error message: It contains the text “Problem executing component: Call was rejected by callee. (Exception from HRESULT: 0x80010001 (RPC_E_CALL_REJECTED))” (to help people Googling this error message :-). This “problem” was introduced as we addressed an issue with the way our WPF components in AutoCAD handle inbound messages, largely due to Microsoft’s decision not to support nested message loops in WPF. If WPF is... Read more →

Updated DevTV: AutoCAD VBA to VB.NET Migration Basics

After one update to the content he originally posted, Stephen Preston has handed the reigns for this DevTV across to Augusto Gonçalves, a São Paulo-based member of our DevTech Americas team. Augusto presented his work to rave reviews at AU 2009, and has now updated the online DevTV content. I’ve gone ahead and updated the original post to point to this new content, but here are the links, for your convenience: AutoCAD VBA to VB.NET Migration Basics view download (44.7 Mb) Aside from upgrading the presenter (sorry, Stephen – I couldn’t resist ;-) we’ve made some additional enhancements in... Read more →

Creating demand-loading entries for .NET modules from outside of AutoCAD

I received a really intriguing question by email from Dave Wolfe on Friday afternoon: Due to your post on the topic, I wanted to improve my installation method for .Net modules. While examining the topic, I ran into a few concerns that shaped my development process. The game changer is that I couldn’t find a way to use reflection to check a .net module for the CommandMethodAttributes without being in an AutoCAD session. The CommandMethodAttribute crashes on initialization outside of AutoCAD. Dave went on to describe a couple of ways he’d found to work around this problem by driving... Read more →

The Stephen and Fenton Show: ADN DevCast Episode 1

You may or may not be aware that my team, DevTech, writes and publishes DevNotes on the ADN website, answers support questions submitted by ADN members using a tool we call DevHelp Online, records DevTV sessions, participates in events known as DevLabs, talks about our upcoming products at DevDays and delivers API training. (Seems like we need to get the branding police to work on that last one. :-) So, in keeping with our theme we have started a new activity… I’m proud (and not unamused, which is putting it mildly) to announce our first DevCast. Recorded recently by... Read more →

Fun with multi-touch and Alias Sketch for AutoCAD

Over the holiday season I bought myself an external 21.5” LCD multi-touch screen from Albatron. I’d been meaning to play around with multi-touch technology (on a full PC rather than a smartphone) and the arrival of Alias Sketch for AutoCAD 2010 on Autodesk Labs seemed like the perfect opportunity. AutoCAD doesn’t currently have in-built multi-touch support – and therefore neither does the version of Alias Sketch that works inside it – but at least the single-touch capabilities of the screen would give me the chance to flex a few of my (admittedly somewhat atrophied) artistic muscles. To get started... Read more →

Getting the list of .NET assemblies loaded into AutoCAD from LISP

A big thank you to Jim Cameron from Dematic for providing the code for this post, and to Wayne Brill from DevTech Americas who helped him on his way via ADN support. I’ve made a few changes of my own to the code, but the concept is very much Jim’s. Jim recently had a frustrating problem with a VLX application he wrote that depends – via (vl-arx-import) – on a .NET module. It turns out the module was not being demand-loaded properly, but this took some time to diagnose. In the past Jim used (arx) from LISP to detect... Read more →

Watching for deletion of a specific AutoCAD block using .NET

I received this question by email from Vito Lee: I am trying to write an event handler function in C# and can use your expertise. I am trying to display an alert box whenever a user erases a specific block in a drawing. Which event handler would be best for this situation? This one is interesting, because it’s quite a general problem and there are a few ways to solve it. To start with, let’s generalise the problem description to cover watching for editing operations on drawing objects. We’re indeed going to solve the specific problem stated above –... Read more →

An entomologist’s view of Project Butterfly

Thanks to Jim Quanci for helping with the title of this post. My working title was “Pulling the wings off Project Butterfly” (ouch) but that clearly wasn’t going to fly (groan :-). A few weeks ago I had a long discussion with Tal Weiss, one of the co-founders of the company Autodesk recently acquired along with the technology that has become Project Butterfly. Tal provided me with some very interesting background information as to Butterfly’s architecture, which I thought I’d share with you. Tal tells me that Jonathan Seroussi, who also joined Autodesk with the acquisition, has been the... Read more →

Testing truth

This is a minor pet peeve of mine that I felt like sharing. Feel free to post a comment if you agree, disagree or have your own pet coding peeve to share with other readers of this blog. I quite often see .NET code that tests for the value of a Boolean to see whether it’s true or false: if (booleanVariable == true) { … } or If isBooleanFunction() = False Then … End If Now while not strictly incorrect, this style is, at least, redundant: a Boolean is by nature true or false, and testing for equality with... Read more →

Debugging into AutoCAD’s .NET API layer using Reflector – Part 2

In the first post in this series we looked at the basic (and free) capabilities of the upcoming version 6 of .NET Reflector. Today we’ll look at the “Pro” capabilities, which integrate decompilation with debugging of 3rd party assemblies. To get started, we should see a new “.NET Reflector” toolbar inside our Visual Studio installation. On it, we should see a “Choose Assemblies to Debug…” option: This option launches an analysis of our currently open solution, to understand the assemblies that have been referenced inside it: One very important thing to note: for Reflector to work, you must have... Read more →

Debugging into AutoCAD’s .NET API layer using Reflector – Part 1

As many of you will know, by now, I’m a big fan of Reflector. I’ve used it for quite some time, since its early days as a piece of freeware developed by Lutz Roeder, and overall it’s proven to be an extremely valuable tool. When a UK-based company, Red Gate Software, acquired the Reflector technology back in 2008, I was curious as to their strategy for monetizing it (and it seems I wasn’t alone in speculating on the direction the tool would take as a commercial offering). Well, that’s now starting to become clear with the Beta release of... Read more →

Extending a set of AutoCAD lines using .NET

Thanks to Stephen Preston from DevTech Americas for the code that originally inspired this post. A nice little one to start the week. We’re going to ask the user to select a bunch of lines and we’ll then go through and edit each one, extending it in both directions by a quarter of its original length. The code shows a couple of interesting techniques: aside from extending the lines themselves we also use a SelectionFilter in combination with a PromptSelectionOptions object to restrict the selection process from selecting anything but lines (and to give a customized experience by changing... Read more →