Through the Interface

Calling AutoCAD commands from .NET

In this earlier entry I showed some techniques for calling AutoCAD commands programmatically from ObjectARX and from VB(A). Thanks to Scott Underwood for proposing that I also mention calling commands from .NET, and also to Jorge Lopez for (in a strange coincidence) pinging me via IM this evening with the C# P/Invoke declarations for ads_queueexpr() and acedPostCommand(). It felt like the planets were aligned... :-) Here are some ways to send commands to AutoCAD from a .NET app: SendStringToExecute from the managed document object SendCommand from the COM document object acedPostCommand via P/Invoke ads_queueexpr() via P/Invoke Here's some VB.NET... Read more →

Calling DIMARC from Visual LISP

This is an interesting little problem that came in from Japan last week. Basically the issue is understanding how to call the DIMARC command programmatically from LISP using (command). The DIMARC command was introduced in AutoCAD 2006 to dimension the length of arcs or polyline arc segments. What's interesting about this problem is that it highlights different aspects of entity selection in LISP. Firstly, let's take a look at the DIMARC command (I've put the keyboard-entered text in red below): Command: DIMARC Select arc or polyline arc segment: Specify arc length dimension location, or [Mtext/Text/Angle/Partial/Leader]: Dimension text = 10.6887... Read more →

Selecting the edge of a nested solid in ObjectARX

This entry was contributed by Adam Nagy, a member of DevTech EMEA based in Prague. The question is really a combination of two problems: Selecting a subentity Selecting a nested entity Selecting a subentity First we should clarify what a subentity is: A subentity is a pseudo entity which is a logical part of a real entity. In our sample drawing the solid is the real entity [AcDb3dSolid] and the edge is the pseudo entity (there is no AcDbEdge class). In AutoCAD we rely on IDs called GS (short for graphics system) markers to get to these subentities. The... Read more →

More fun with Autoexp.dat - let's see those resbufs

I had a nice surprise this weekend. Jorge Lopez, an old friend and colleague, had been reading this blog entry and decided to create a Visual Studio AddIn that allows you to see resbufs content expanding automatically while debugging. Jorge and I go back a long way - he used to work in DevTech (before it was called that) in our Americas team, back when I was based in Europe the first time. He later went on to join AutoCAD Engineering, and was one of the key contributors to AutoCAD's COM Automation API (although back then it was called... Read more →

Supporting multiple AutoCAD versions - conditional compilation in C#

Someone asked by email how to get the block import code first shown last week and further discussed in yesterday's post working with AutoCAD 2006. I've been using AutoCAD 2007 for this, but to get it working there are only a few changes to be made. Firstly you'll need to make sure you have the correct versions of acmgd.dll and acdbmgd.dll referenced into the project (you should be able to tell from their path which version of AutoCAD they were installed with). Secondly you'll need to modify your code slightly, as WblockCloneObjects() has changed its signature from 2006 to... Read more →

Breaking it down - a closer look at the C# code for importing blocks

I didn't spend as much time as would have liked talking about the code in the previous topic (it was getting late on Friday night when I posted it). Here is a breakdown of the important function calls. The first major thing we do in the code is to declare and instantiate a new Database object. This is the object that will represent our in-memory drawing (our side database). The information in this drawing will be accessible to us, but not loaded in AutoCAD's editor. Database sourceDb = new Database(false, true); Very importantly, the first argument (buildDefaultDrawing) is false.... Read more →

Import blocks from an external DWG file using .NET

We're going to use a "side database" - a drawing that is loaded in memory, but not into the AutoCAD editor - to import the blocks from another drawing into the one active in the editor. Here's some C# code. The inline comments describe what is being done along the way. Incidentally, the code could very easily be converted into a RealDWG application that works outside of AutoCAD (we would simply need to change the destDb from the MdiActiveDocument's Database to the HostApplicationServices' WorkingDatabase, and use a different user interface for getting/presenting strings from/to the user). using System; using... Read more →

Handling Automation errors in Visual LISP

Since Visual LISP was introduced, developers have taken advantage of its ability to call COM Automation interfaces (whether AutoCAD's or other applications'). The addition of this functionality to the LISP platform created many new development possibilities - previously you were able to call through to ObjectARX applications defining LISP functions, but enabling Automation access from LISP suddenly allowed developers to access any other application adopting the COM standard its API, such as Microsoft Excel. A quick note on error handling in LISP... Traditionally LISP applications have defined their own (*error*) function to trap errors during execution. During this function... Read more →

Cancelling an active command in AutoCAD

Thanks to Alexander Rivilis for this topic (he submitted a comment to my previous post that got me thinking about this addendum). When you're asking AutoCAD to execute commands by submitting them to its command-line, it helps to make sure no command is currently active. The accepted approach is to send two escape characters to the command-line... this is adopted by our menu & toolbar macros that consistently start with ^C^C in MNU and now CUI files. Why two? The first is to cancel the "most active" command, and the second is to drop out of either the dimension... Read more →

Techniques for calling AutoCAD commands programmatically

It's quite common to want to call commands from one or other of AutoCAD's programming environments. While it's cleanest (from a purist's perspective) to use an API to perform the task you want, the quickest way - and the one which will appeal to the pragmatists (and the lazy) among us is often to call a sequence of commands. And there are, of course, a few places in AutoCAD where APIs have not been exposed, so scripting commands is the only way to achieve what you want. Let's take the simple example of adding a line. Here's what you'd... Read more →

Developing Autodesk Civil 3D applications with .NET

Thanks to Scott Wolter from Digital Vellum for suggesting this topic, and to Partha Sarkar (a member of the DevTech team in Bangalore, India) for contributing it... Welcome to the world of developing Autodesk Civil 3D 2007 applications with Visual Studio .NET. Autodesk Civil 3D provides interop assemblies that expose its COM interfaces for use from .NET technologies, such as VB.NET, C#. Before you start developing .NET applications for Autodesk Civil 3D 2007, I strongly recommend you apply the Autodesk Civil 3D 2007 Service Pack 1A, otherwise you may find some issues in referencing the Civil 3D TLB files... Read more →

Some cool copy/paste tools for Visual Studio

I won't tell you just how bored I've been getting while "post-processing" the HTML created when I copy/paste code from Visual Studio into this blog's editing interface. My aim is simply to maintain a certain amount of the formatting provided in Visual Studio (font, syntax colouring and indentation would be great, but I end up settling for the last two, and only then after a lot of HTML editing). So I decided to take a look at what tools might be out there on the web to help with this. The first tool I found wasn't what I wanted,... Read more →

Apples and Fireworks

[ Warning: this post is largely frivolous and non-technical, so please don't read on if that is likely to bother you. :-) ] Yesterday was August 1st, the Swiss National Day. During the afternoon, we (my wife, our 2 year-old son and I) visited my wife's parents at their place in the hills just outside Neuchâtel. My father-in-law gave me a fantastic present that I'm yet (but impatient) to play with: an Apple Newton in mint-condition. In the evening we went down to St Blaise, on the edge of Lake Neuchâtel, to watch the town's annual firework display. The... Read more →