Through the Interface

Generating larger preview images for all blocks in an AutoCAD drawing using .NET

There was an interesting coincidence, earlier in the week. A blog comment came in on an old post on the exact day there was an internal email discussion on the same topic. The post was about using the BLOCKICON command on a document that gets loaded into the editor just for that purpose, generating a thumbnail image on disk for each of the contained block definitions. The problem with this approach – as was suggested by a couple of people in blog comments – is that the generated thumbnail is really small at just 32 x 32 pixels. The... Read more →

Querying for XCLIP information inside AutoCAD using .NET

This question came in recently by email: I have reached a snag when trying to find the boundaries of external references that have been "xclipped" by the user. Or, to be more precise, I can't even really find the data telling me whether or not the external reference has been "xclipped" at all. I'm wondering if you have any idea how or where I could find this data. While I found this previous post showing how to perform an XCLIP, I couldn’t find anything showing how to query for XCLIP information. Here’s some C# code that does just that... Read more →

Creating a selection filter that finds dynamic blocks in AutoCAD using .NET

An interesting question came in via email from Rob Outman. He’s interested in applying a selection filter when the user selects dynamic blocks. This is straightforward for unmodified dynamic blocks – just as with standard blocks, you can filter on the block name very easily – but it works less well on dynamic blocks whose properties have been modified at an instance level. Essentially what happens is this: if you select a block reference to a dynamic block in the AutoCAD editor and then use (for example) the Properties window to edit some of the custom properties associated with... Read more →

Generating preview images for all blocks in an AutoCAD drawing using .NET

This was a nice little solution I saw provided recently by Viru Aithal from DevTech India. It’s a simple command to open a drawing and generate preview icons for each of the blocks it contains. It forces an icon to be generated – when it doesn’t already exist – via Viru’s old trick of using InvokeMember() to call IAcadDocument::SendCommand() via COM (which is synchronous, where Document.SendStringToExecute() is asynchronous and only executes once the command has completed). Viru’s trick allows him to call SendCommand() without creating a dependency on the AutoCAD Type Library (something developers often prefer to avoid, as... Read more →

Creating a legend of AutoCAD drawings using .NET

This interesting question came up in our discussion forums: Does anyone have a routine that will insert all the drawings from a single folder into one drawing to create a legend sheet? I'm trying to document the company's various blocks and details for dissemination amongst several offices. The simplest – and most elegant, in my opinion – approach for addressing this requirement is via the Table object, which allows you to include block thumbnails in each of its cells. So we would need to import the various drawings into the current drawing as blocks, and then point the various... Read more →

Exploding AutoCAD objects using .NET

Time to go back to basics. I realised recently – on receiving this comment – that I hadn’t specifically covered the nature of Entity.Explode() in a post (even if it’s been used in a few of them, over the years). Entity.Explode() is one of those tricky methods: it’s actually a faux-ami with the AutoCAD command of the same name, in a very similar way to Database.Purge(). The way in which Explode() and Purge() differ from their “equivalent” commands is that they’re non-destructive: they don’t actually result in a change to the AutoCAD drawing database. Explode() populates a DBObjectCollection with... Read more →

Gathering points defining 2D AutoCAD geometry using .NET

The reason for this post may be obvious to some – probably those who are doing this kind of analysis already – and less obvious to others – who will have to wait for the next post to see why it’s helpful. :-) I won’t ruin the surprise, but suffice it to say that for various types of spatial analysis it’s helpful to acquire first points from geometry. This post attempts to do that for 2D geometry, and hopefully deals with a few of the trickier cases related to rotated text and such-like. For this particular task I chose... Read more →

Combining AutoCAD blocks in separate files into a single DWG using .NET – Take 2

Thanks for Chris, Dan and Dale for pointing out the obvious issue(s) with my last post. Let’s just blame it on a few holiday cobwebs needing brushing away during the first week back in the saddle. :-) The main issue with my previous implementation was that I’d somehow forgotten that Database.Insert() allows you to insert into a named block definition. This simple function does all my previous, manual approach did and more. The secondary issue – but still very important to those using annotation scaling – is that the previous code does not work for annotative blocks, as Dan... Read more →

Combining AutoCAD blocks in separate files into a single DWG using .NET

Important note: the code in this post – while potentially interesting, at a certain level – has been superceded by the code in the following post. Please go ahead and use that simpler, more complete implementation instead. This question came in, over the holidays, that seemed like it was worth addressing: How do I get an external DWG into the blocks table as a block definition? I started by quoting this ancient (at least in terms of this blog) post, but it turned out only to be of partial help: the problem is that the external DWG does not... Read more →

Adding a 2D spatial filter to perform a simple xclip on an external reference in AutoCAD using .NET

I’ve now checked in for my flight to Las Vegas – and, thanks to Jeremy Tammik’s recent troubles, I luckily renewed my ESTA – so I’m pretty much all set for my trip to AU 2010, at least from a travel perspective. I’m just keeping my fingers crossed that the gastric 'flu my kids seem to have come down with doesn’t hit me before I leave (or once I’m at AU… what a grim thought). I was going to keep today’s post light, just like the last one, but then decided to dip into my email folder of externally... Read more →

Previewing the contents of the clipboard in an AutoCAD palette using .NET

I’ve been meaning to attack this one since we first published the Clipboard Manager as a Plugin of the Month: working out how to display a preview image of the clipboard contents inside the Clipboard Manager palette. And then I happened to receive a request by email, yesterday, suggesting a couple of enhancements to the tool. A nice reminder. :-) 1. Have the clipboard include image previews, similar to that of the wblock command (instead of needing to immediately rename the item when fast copying multiple items). 2. Have the clipboard store items in memory for use in between... Read more →

September’s Plugin of the Month: DigSigStamp

Yesterday Scott Sheppard announced the availability of this plugin over on It’s Alive in the Lab. We originally received a request for this Plugin of the Month some time ago. Fenton Webb, from our DevTech Americas team, developed the initial version using an ObjectARX custom entity – as the requester required support for versions of AutoCAD prior to 2010 – but for this public release, Stephen Preston went ahead and re-implemented the mechanism in a .NET application using the Overrules API introduced in AutoCAD 2010. This plugin basically allows you to see graphically when an AutoCAD drawing is digitally... Read more →

Changing the layer or color of a nested entity using .NET (take 2)

A big thanks to Thorsten Meinecke for pointing out the obvious issue with my prior post (the nested entity selection loop which has frustrated me unnecessarily when developing the code for that post and another). Here are the details of the fix: using Editor.GetNestedEntity() along with a PromptNestedEntityOptions object, instead of a direct message string, allows us to specify AllowNone to be true. Which, in turn, causes PromptStatus.None to be returned when the enter or space keys are used to terminate the selection loop. An obvious omission, in hindsight, but anyway – I’m much obliged to you, Thorsten! :-)... Read more →

Detaching an AutoCAD external reference using .NET

Here’s some simple C# code that asks the user to select an external reference and then detaches it from the current drawing: using Autodesk.AutoCAD.Runtime; using Autodesk.AutoCAD.ApplicationServices; using Autodesk.AutoCAD.DatabaseServices; using Autodesk.AutoCAD.EditorInput; namespace XrefApplication { public class Commands { [CommandMethod("DX")] static public void DetachXref() { Document doc = Application.DocumentManager.MdiActiveDocument; Database db = doc.Database; Editor ed = doc.Editor; // Select an external reference Transaction tr = db.TransactionManager.StartTransaction(); using (tr) { BlockTableRecord btr = null; ObjectId xrefId = ObjectId.Null; // We'll loop, as we need to open the block and // underlying definition to check the block is // an external reference during... Read more →

Swapping AutoCAD block attribute order using .NET

A big thanks to Philippe Leefsma, from the DevTech team in Europe, for providing this handy piece of code in a response to an ADN member. In the last post we saw some code that made use of DBObject.HandOverTo() to maintain identity between an old line and a new one with which we wanted to replace it. This code makes use of this method’s counterpart, DBObject.SwapIdWith(), which works on two database-resident objects (rather than the replacement being in-memory, as is the case with HandOverTo()). Here’s C# code implementing two commands, to swap the identity (and therefore the order) of... Read more →

Changing the layer of an entity in an AutoCAD block using .NET

After seeing Shaan list the results of the latest AUGI wishlist, I started thinking about which of the items would be worth covering either on this blog or via a Plugin of the Month. The second item on the list, “Automatically Differentiate Manually Edited Dimensions”, has (hopefully) been addressed by Dimension Patrol, this month’s Plugin of the Month, so that’s a good start, anyway. The first item, “Change Objects in a Block to a new Layer”, seemed as good a good place to start as anywhere. Here’s some C# code that builds upon a technique for selecting/highlighting nested entities... 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 →

Creating an AutoCAD group using .NET

In the last post we looked at some code to define a block and insert it into the model-space of an AutoCAD drawing. Today we’re going to look at creating a group. Before we dive into the code, it’s worth taking a quick look at the difference between a block and a group, to understand the differences between these two container/aggregator objects. I know that much of this information is available elsewhere, but hey – I’m on a roll, so I request your forbearance. Let’s start with looking at the top-level structure of an AutoCAD Database (which is equivalent... Read more →

Creating an AutoCAD block using .NET

This post – and its sister post, which will cover creating a group – are further topics I would expect to have already covered in this blog at some point, or perhaps to see covered by the AutoCAD .NET Developer’s Guide (and I’m sure they will be in a future incarnation of it). So thanks to Adam Nagy, from DevTech EMEA, for suggesting these topics. It’s nice to go back to basics once in a while (although this means I do have to beg the patience of the readers out there who know this stuff inside out). So, here’s... Read more →

Adding block and xline offset support to the OffsetInXref Plugin of the Month

In response to September’s Plugin of the Month - which Shaan has very kindly posted about over on Between the Lines – a few people have requested enhancements to the OffsetInXref tool. Two came up, in particular: The ability to offset the contents of blocks, not just xrefs The ability to enable the XLINE command’s offset functionality to work with xrefs (and blocks) The changes to enable these enhancements are very minor, which is always a pleasant surprise. Well, in the first case it isn’t much of a surprise: xrefs are actually just a special kind of block, so... Read more →