So far, we have covered ten of AutoCAD standard object selection options. Remember, I am numbering them to prove that there really are eighteen different options you can use at AutoCAD’s “Select objects: “ prompt. This month we’ll cover the last eight, which includes one option that I hardly knew anything about. Sadly, I still don’t!

As you go about selecting objects, you will inevitably pick the wrong object. The Remove (11) option allows you to “unselect” or remove objects from the current selection set. Notice that the prompt changes to say “Remove objects: “.

If you do use the Remove option, and you want to go back to adding objects to your selection, then you would use the “Add” (12) option. This is AutoCAD’s default selection mode unless the PICKADD sysvar is set to 0.

There are a couple other ways to remove objects. If you hold down the Shift key, AutoCAD will unselect any object that you select. And, believe it or not, you can actually “undo” an object selection! Undo (13) is a valid selection option; it removes the last selected object. If you are in the “Remove objects” mode mentioned earlier, undo will “add” the last removed object! Control-Z will work as well.

Most of the object selection options that we’ve discussed in this and the previous article require that you be able to see the actual objects in order to select them. There are times, though, when you may have an object in a drawing that you can’t see, and therefore cannot select. The most common type of object would be a piece of text. I don’t know how it happens, but I have seen numerous occasions where there were pieces of text that either have nothing in them or have simply a space or two. I’ve also found blocks that have no entities in them. Out of sight, out of mind, right? Not so fast. You now have a text style, block or layer that can’t be purged. Still no big deal? Try this. Insert this drawing (containing “invisible” objects) into another drawing as a block. Zoom extents, make sure all the layers are on, explode the block and, using a “Window” selection, erase everything you can see. Guess what just got left behind; all the “invisible” objects! I have seen these number in the thousands in some client drawings. Do this a few times and these entities will build up

The ALL (14) option allows you to select objects that you can’t see. In the example drawing above, start the Erase command again. Now at the “Select objects: “ prompt, type ALL. AutoCAD will now select all the objects that you cannot see. The ALL option can actually be used to help clean up a drawing. For example, in a drawing that you might suspect as having some hidden objects, start the erase command. Use the ALL selection option (it will return “# found”). Now, type “R” (for remove) and select everything you can see in the drawing. So, the selection set now consists of all the entities that you cannot see. Hit Enter to finish the Erase command. Word of caution: It would be a good idea to thaw and turn on everything before you do this!

Selecting objects in complex areas can be time consuming. It can be frustrating too, when you get done with a tedious selection, only to notice that you missed a few objects (or have too many). The Previous (15) option will allow you to re-select the objects that you just selected, then add or remove objects from the set. Here’s an unusual use for this option. After exploding a block, the Previous option will select all the individual objects that were in the block!

The Fence (16) selection is quite unique. You select objects simply by “drawing” a selection line across them. One thing to watch out for; if you are attempting to select objects that have hidden lines, if your fence line crosses at one of the gaps, the object won’t be selected.

Groups are one of those rarely used concepts in AutoCAD (might be a good future TIPniques topic). It offers a way to “group” objects together without some of the limitations (and benefits) of using a block. The group (17) option permits you to select a group by its name. You can use wildcards to select groups that are named similarly.

The last selection option is one that I have never used. Nor have very many others, it seems. I did some searching across the web and on newsgroups, and couldn’t find anything (and that doesn’t happen very often!). In fact, AutoCAD’s online help is on it is pretty sparse. I’m talking about the Class (18) option. Heard of it? At the risk of revealing my ignorance on the topic, I’ll attempt to explain it. AutoCAD has the ability to connect objects to an external database, enabling it to do some pretty impressive things. The Class selection allows you to select specific objects that are connected to a database. When I attempted to use this option, I got slapped with a message that said “no current classification schema”. All I can figure is that I got this message because my drawing was not connected to a database. I didn’t take the time to connect to a database and see what would happen then, so I don’t know. I’m sure I’ll find out after some of you read this article. I’d be glad to hear from you.

So, there are your standard options for selecting objects in AutoCAD. Told you there were eighteen! I say “standard” because there are ways using AutoLisp functionality to select objects. But these will have to wait for another time. Happy selecting…

Submitted by Chris Lindner, a veteran AutoCAD user, consultant, trainer, and AUGI Director in 2003.