AutoCAD Plus: What You Get When You Add.NET!

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1 11/30/2005-1:00 pm - 2:30 pm Room:N. Hemispheres (Salon E1) (Dolphin) Walt Disney World Swan and Dolphin Resort Orlando, Florida AutoCAD Plus: What You Get When You Add.NET! Clayton Hotson - Autodesk CP33-3 This class will introduce you to the hottest thing in the high-tech world:.net. We'll look at how the AutoCAD team -- and every Autodesk engineering team that bases technology on the AutoCAD platform -- is using.net technology to make your life easier. This class is for anyone who customizes AutoCAD using LISP, VB / VBA, or ObjectARX. About the Speaker: With more than 15 years in the software industry, Clayton has a unique background in Remote- Sensing/GIS, oceanographic survey data, and drafting applications. He originally specialized in developing navigation and instrumentation software for the PC platform. Over the years, he has gained fluency in several programming languages. Clayton's current focus is on APIs relating to AutoCAD-based products, as well as COM and.net technology. An accomplished trainer and consultant, he has taught API classes, ObjectARX programming, and.net seminars -- via the Web and in person -- to AUGI members and Autodesk Developer Network partners throughout the Americas.

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3 AutoCAD Plus: What you get when you add.net Agenda: AutoCAD 2006 VB.NET Project Setup Basics Where do I start? Prerequisites, starting a project and basic setup. Writing to the AutoCAD Commandline Creating an AutoCAD command Where to get help - Documentation and samples! Getting input from the AutoCAD Commandline Hello [Name] Modal/Modeless Forms in AutoCAD Hello Form! Alert Dialogs Sidebar Useful settings Launching AutoCAD from the editor Running your code at module-load Auto-Load or Demand Load your app at AutoCAD startup! Modeless Dockable Form Hello Docking Form Peeking into the AutoCAD Database Understanding the Database Structure Iterate Blocks and Print them out Creating AutoCAD Entities Hello Text Create a text style! 2

4 AutoCAD 2006 VB.NET Project Setup Basics AutoCAD Plus: What you get when you add.net Prerequisites: AutoCAD 2006 and Visual Studio 2002, 2003 or Figure 1 In your VB editor, use the New Project Wizard to create your project in Visual Studio. Select the VB.NET Class Library project type (shown in fig. 1). If you have installed the ObjectARX Wizard (free at ) you can select the AutoCAD Managed VB Project Application to create the project, and make the basic settings. The only absolute dependencies our project has for AutoCAD development is to reference the managed AutoCAD assemblies acdbmgd.dll and acmgd.dll located in the AutoCAD install folder. Use the solution explorer to add these references manually (note the ARX/.NET Wizard does this for us). However, we can significantly shorten the amount of typing we require by Importing the namespaces defined within these assemblies. The most typical imported namespaces for AutoCAD are shown and described in the figure below. Once you have these two basic tasks done, we are free to begin coding for AutoCAD! 3

5 Writing to the AutoCAD Commandline AutoCAD Plus: What you get when you add.net Take a look at the code below which defines a simple function for writing to the AutoCAD commandline: ' Defines a command which posts a message on the AutoCAD command line <CommandMethod("HELLO")> _ Public Sub HelloCommand() Dim ed as Editor = Application.DocumentManager.MdiActiveDocument.Editor ed.writemessage(vbnewline + "Hello World!") ;Editor s WriteMessage member How do I load and run the project in AutoCAD?? In AutoCAD, loading.net managed assemblies is done via the NETLOAD command. Once loaded, any commands or forms defined in the project can be run. (See the sidebar for notes about auto-loading). Where to get Help!! VB.NET s editor includes Intellisense, which greatly reduces the need to look for function definitions and argument types, however it is inevitable that you will require help for AutoCAD programming. The Help for the AutoCAD.NET API is distributed as part of the ObjectARX SDK (free at ). There is a section within the documentation entitled ObjectARX Managed Wrapper Classes which gives a great introduction to the API. Also included in the ObjectARX SDK are numerous.net samples which demonstrate the API s capabilities. See the samples under the ObjectARX\Samples\dotNet folder. Getting input from the AutoCAD Commandline Here is some code which demonstrates a couple representative methods for obtaining user input on the commandline. There are many more prompt types available (real, angle, distance ), but the code below demonstrates the basic usage for nearly all of them. See the Prompts SDK sample for detailed usage of each of these. <CommandMethod("HELLO")> _ Public Sub HelloCommand() Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor 'Prompts for your name and prints it back to the commandline Dim NameResult As PromptResult = ed.getstring("what is your name? ") ed.writemessage(vbnewline + "Hello " + NameResult.StringResult) 'Prompts for your age and prints it back to the commandline - using options to constrain Dim AgeOptions As New PromptIntegerOptions(vbNewLine + "What is your age?") AgeOptions.AllowZero = False 'No babies allowed :-) Dim AgeResult As PromptIntegerResult = ed.getinteger(ageoptions) 'Get the value ed.writemessage(vbnewline + "You entered " + AgeResult.Value.ToString) 'Print it back 4

6 AutoCAD Plus: What you get when you add.net Modal/Modeless Forms Using the VB editor, it is extremely easy to create user forms and dialogs with the visual tools. To add a form, simply right click on the project name within the solution and select Add new Item Add new Form. You can then use the Toollbox to add controls directly to the form. Displaying these forms in AutoCAD is even easier. Here is the relevant code associated with displaying a modal form in AutoCAD using the.net API: <CommandMethod("HELLOFORM")> _ Public Sub HelloForm() Dim form As New Form1() Application.ShowModalDialog(form) Application.ShowModelessDialog(form) Modeless version is the same Why not use the Form.Show() method? In AutoCAD, this is not supported, and can lead to unexpected behavior. The added benefit of using the AutoCAD API to display the form is that AutoCAD remembers the size and location of the form between usages. Sidebar Useful settings Launch AutoCAD to Debug Rather than having to launch AutoCAD from the start menu each time, it is much easier to point the Visual Studio editor to AutoCAD to run when we want to execute. We can do this with a single setting in the project Property Pages. Under Configuration Properties Debugging, set the Start External Program option to point to AutoCAD. 5

7 Running initialization code at module-load time AutoCAD Plus: What you get when you add.net In order to have our form load currently we need to run the HELLOFORM command. Many times it is desirable to run some initialization code (of any kind) when the module is first loaded. Here is the relevant code for this: <Assembly: ExtensionApplication(GetType(vbMgdAuDemo.Class1))> Attribute to speed up load-time Public Class Class1 Implements Autodesk.AutoCAD.Runtime.IExtensionApplication Public Sub Initialize() Implements IExtensionApplication.Initialize HelloForm() Or any other relevant startup code Public Sub terminate() Implements IExtensionApplication.Terminate Code to run during AutoCAD shutdown At module-load time, AutoCAD searches for the IExtensionApplication interface in all exported types from the module. If it is found, it calls the members during startup and shutdown. The IExtensionApplication attribute present simply speeds up the load-time search making for faster loads. The CommandClass attribute is identical, and is used to define modules which define commands, speeding up the load process. Setting up your module for Demand (Automatic) load in AutoCAD To set your module to be loaded automatically by AutoCAD at startup, there are a few registry keys we can set that AutoCAD will search at startup. Generally, it is best to have an installer set these during product installation. Here are the relevant keys demonstrating some settings in AutoCAD [HKEY_LOCAL_MACHINE\SOFTWARE\Autodesk\AutoCAD\R16.2\ACAD-4001:409\Applications\vbMgdAuDemo] "DESCRIPTION"="Autodesk University Test Application" "LOADER"="C:\\My Documents\\_Temp Visual Studio Projects\\vbMgdAuDemo\\bin\\vbMgdAuDemo.dll" "LOADCTRLS"=dword: e "MANAGED"=dword: [HKEY_LOCAL_MACHINE\SOFTWARE\Autodesk\AutoCAD\R16.2\ACAD-4001:409\Applications\vbMgdAuDemo\Commands] "HELLOFORM"="HELLOFORM" [HKEY_LOCAL_MACHINE\SOFTWARE\Autodesk\AutoCAD\R16.2\ACAD-4001:409\Applications\vbMgdAuDemo\Groups] "VBMGDAUDEMO_CMDS"="VBMGDAUDEMO_CMDS 6

8 AutoCAD Plus: What you get when you add.net Modeless Dockable Form With only a little more work than it took to make a modeless dialog, we can make our modeless dialog a dockable palette window, which looks and behaves the same as the standard AutoCAD palette windows. We can add controls and handle messages just as we would a standard form, but AutoCAD controls the way it interacts with the frame. Below is the relevant code which demonstrates how: Shared ps As PaletteSet = Nothing 'Since we're modeless, we should have a shared variable for this <CommandMethod("HELLOFORM")> _ Public Sub HelloForm() If ps Is Nothing Then 'If the command has never been run... ps = New PaletteSet("Test Palette Set") ps.style = PaletteSetStyles.ShowAutoHideButton Or PaletteSetStyles.ShowCloseButton ' There are many other styles available as well! See the docs ps.minimumsize = New System.Drawing.Size(300, 300) Set the form to 300x300 pixels ps.add("test Palette 1", New TestControl()) TestControl is a User Control created in the resource editor End If ps.visible = True 'Whether the command was run or not, show the form - it is never destroyed. For more details about this functionality, see the DockingPalette SDK sample. 7

9 Peeking into the AutoCAD Database AutoCAD Plus: What you get when you add.net The AutoCAD database is comprised of a set of symbol tables, each of which contain relevant records representing entities, objects and the containers which hold them. For instance, each AutoCAD Layer exists as a Layer Table Record contained within the one and only Layer Table database table. Similarly AutoCAD Blocks exist as Block Table Records within the single Block Table (for detailed information about the structure of the database and these tables, see the ObjectARX Developer s guide free at As developers, we access the tables basically the same way. The only difference is knowing how the various tables relate to each other. In this example, we take our first look into the AutoCAD database by simply listing out all the blocks in the current drawing. The example demonstrates how to access the current database, and individual database-resident objects within it using a.net transaction. Transactions are necessary mechanisms to work with, and are actually really easy and useful once you get the hang of them. Here is the relevant code which prints out the blocks to the commandline: <CommandMethod("LISTBLOCKS")> _ Public Sub ListBlocks() Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor Dim db = HostApplicationServices.WorkingDatabase 'Get the current AutoCAD Database Dim trans As Transaction = db.transactionmanager.starttransaction() 'Start the db transaction. Try Dim bt As BlockTable = trans.getobject(db.blocktableid, OpenMode.ForRead) 'Get the Block Table Dim id As ObjectId 'Declare an ID to represent each block. For Each id In bt 'for each block in the block table Dim btr As BlockTableRecord = trans.getobject(id, OpenMode.ForRead) 'Get the Block Table Record ed.writemessage(vbnewline + "Block Found: " + btr.name()) 'Write out its name Next trans.commit() 'we're done - no errors Catch MsgBox( Error! ) 'something went wrong! trans.abort() Finally trans.dispose() 'cleanup - if an exception was thrown, this will clean up everything too. End Try (Note to use these.net types, you will need to import another namespace The Autodesk.AutoCAD.DatabaseServices namespace defines all of the new types we use in the above function. Take a look at what is happening here. We declare a Transaction object using the current database. From then on, whenever we need to access any database resident object, we use the transaction object ( trans ) using the GetObject method. Notice also that no cleanup is ever performed; this is because the transaction object will do that for us and what is especially convenient is the it will handle cleanup even if catastrophic errors occur, so long as we use the transactions properly. The above example will cleanly handle any errors that occur within the function. Notice also that we use two different types of objects to represent a database resident object. Once for when it is transactionresident and one when it is not. When we use a transaction to obtain a reference to a specific entity type (such as a BlockTableRecord shown above) we can dimension a reference type to do it, and use the references members and properties as we normally do in.net. However, we need a way to identify objects uniquely before we assign a reference to them. For this we use the ObjectId reference or moniker type. Get used to this type it is ubiquitous in AutoCAD programming. In the above example, we simply use the id as a convenience for the iterator to use all we do is pass it to the transaction to obtain our reference. 8

10 AutoCAD Plus: What you get when you add.net The design pattern for the transaction usage, the exception handling and the iterator pattern (for-each-next) is very common in the.net for AutoCAD API, so is a good guide for coding in AutoCAD. See the various.net SDK samples for more examples. Adding to the AutoCAD DWG Database The next step into understanding and using the database is to demonstrate how to add a single entity to the database. The MODEL_SPACE block table record is a block just like any other block (as you can see from the LISTBLOCK example). The only difference is that this block cannot be purged, and always represents the Model view in AutoCAD. Any entity in Model space is visible in the Model View. Accessing the MODEL_SPACE block table record is just 1 additional step beyond what we have already done to traverse the blocks in the last step. Once we obtain MODEL_SPACE, it is very easy to add entities to it. The following example code demonstrates how you can use the same transaction/exception design pattern to drill down into the database and add a single piece of text to MODEL_SPACE. <Autodesk.AutoCAD.Runtime.CommandMethod("HELLOTEXT")> _ Public Sub HelloText() Dim db As Database = HostApplicationServices.WorkingDatabase 'Get the AutoCAD Database Dim trans As Transaction = db.transactionmanager.starttransaction() 'Start the db transaction. Try Dim bt As BlockTable = trans.getobject(db.blocktableid, OpenMode.ForRead) 'Get the Block Table Dim btr As BlockTableRecord = trans.getobject(bt(btr.modelspace), OpenMode.ForWrite) 'Get Model Space! 'Create the new text and set its dimensions Dim text As New MText() text.location = New Point3d(15, 15, 0) text.textheight = 2.0 text.contents = "Hello World!!" ' Append entity to model space, and let the transaction know about it btr.appendentity(text) trans.addnewlycreateddbobject(text, True) trans.commit() 'All done - no errors Catch trans.abort() 'Uh oh - error happened - abort the transaction - automatic cleanup Finally ' Finally code is invoked whether there's an error or not trans.dispose() 'cleanup - if an exception was thrown, this will clean up everything too. End Try Note: Use of the Point3d type above requires that we import yet another namespace into AutoCAD. The Point3d, as well as all other geometric types in the.net API are defined within the Autodesk.AutoCAD.Geometry namespace. 9

11 AutoCAD Plus: What you get when you add.net Extra stuff Creating a Font and applying it to our text! Here is an further example of drilling into the database. This next example shows how to create a TextStyleTableRecord and add it to the TextStyleTable, using the same logic and design as above. We ll set the font for this style to be Times New Roman, then assign the text style to the text we created above. Here is the function which creates a new TextStyle, and returns it as an ObjectId. We can use this ObjectID directly to assign to our MText entity. Public Function CreateTextStyle() As ObjectId Dim returnid As ObjectId Dim db As Database = HostApplicationServices.WorkingDatabase 'Get the AutoCAD Database Dim trans As Transaction = db.transactionmanager.starttransaction() 'Start the db transaction. Try Dim st As TextStyleTable = trans.getobject(db.textstyletableid, OpenMode.ForWrite, False) 'Get the Style Table If st.has("mystyle") = True Then returnid = st.item("mystyle") 'If the style already exists, let's use that instead of creating a new one. Else Dim style As TextStyleTableRecord = New TextStyleTableRecord() 'create a new one. style.name = "MyStyle" 'Set the name style.font = New Autodesk.AutoCAD.GraphicsInterface.FontDescriptor("Times New Roman", True, True, Nothing, Nothing) 'Set the font returnid = st.add(style) 'Add the new style to the Style Table trans.addnewlycreateddbobject(style, True) 'Add it to the transaction End If trans.commit() 'All done - no errors Catch trans.abort() 'Uh oh - error happened - abort the transaction - automatic cleanup Finally trans.dispose() 'End the transaction End Try Return returnid End Function We can utilize this function by adding to the HELLOTEXT command the following single line just after we set the contents to Hello World : text.textstyle = CreateTextStyle() Set the text style Questions 10

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