Exploding nested AutoCAD blocks using .NET

csharp

Exploding nested AutoCAD blocks using .NET   Some time ago I posted about how to use Entity.Explode() to do something similar to AutoCAD’s EXPLODE command. At the time it was mentioned in the comments that BlockReference.ExplodeToOwnerSpace() had some relative benefits, but it’s taken me some time to code up a simple sample to show how you might use it (Patrick’s recent comment reminded me I ought to, though).
Anyway, to end the week I thought I’d throw together a quick sample. BlockReference.ExplodeToOwnerSpace() doesn’t return a list of created objects, so I opted to capture this using a Database.ObjectAppended event handler and then recursively call our custom ExplodeBlock() function for any nested blocks that get created. We also then erase the originating entity (or entities, if called recursively), just as the EXPLODE command might.
Here’s the C# code:

2. 
   
3. using Autodesk.AutoCAD.ApplicationServices;
   
4. using Autodesk.AutoCAD.DatabaseServices;
   
5. using Autodesk.AutoCAD.EditorInput;
   
6. using Autodesk.AutoCAD.Runtime;
   
7. namespace Explosions
   
8. {
   
9.   public class Commands
   
10.   {
    
11.     [CommandMethod("EB")]
    
12.     public void ExplodeBock()
    
13.     {
    
14.       var doc = Application.DocumentManager.MdiActiveDocument;
    
15.       if (doc == null)
    
16.         return;
    
17.       var ed = doc.Editor;
    
18.       var db = doc.Database;
    
19.       // Ask the user to select the block
    
20.       var peo = new PromptEntityOptions("\nSelect block to explode");
    
21.       peo.SetRejectMessage("Must be a block.");
    
22.       peo.AddAllowedClass(typeof(BlockReference), false);
    
23.       var per = ed.GetEntity(peo);
    
24.       if (per.Status != PromptStatus.OK)
    
25.         return;
    
26.       using (var tr = db.TransactionManager.StartTransaction())
    
27.       {
    
28.         // Call our explode function recursively, starting
    
29.         // with the top-level block reference
    
30.         // (you can pass false as a 4th parameter if you
    
31.         // don't want originating entities erased)
    
32.         ExplodeBlock(tr, db, per.ObjectId);
    
33.         tr.Commit();
    
34.       }
    
35.     }
    
36.     private void ExplodeBlock(
    
37.       Transaction tr, Database db, ObjectId id, bool erase = true
    
38.     )
    
39.     {
    
40.       // Open out block reference - only needs to be readable
    
41.       // for the explode operation, as it's non-destructive
    
42.       var br = (BlockReference)tr.GetObject(id, OpenMode.ForRead);
    
43.       // We'll collect the BlockReferences created in a collection
    
44.       var toExplode = new ObjectIdCollection();
    
45.       // Define our handler to capture the nested block references
    
46.       ObjectEventHandler handler =
    
47.         (s, e) =>
    
48.         {
    
49.           if (e.DBObject is BlockReference)
    
50.           {
    
51.             toExplode.Add(e.DBObject.ObjectId);
    
52.           }
    
53.         };
    
54.       // Add our handler around the explode call, removing it
    
55.       // directly afterwards
    
56.       db.ObjectAppended += handler;
    
57.       br.ExplodeToOwnerSpace();
    
58.       db.ObjectAppended -= handler;
    
59.       // Go through the results and recurse, exploding the
    
60.       // contents
    
61.       foreach (ObjectId bid in toExplode)
    
62.       {
    
63.         ExplodeBlock(tr, db, bid, erase);
    
64.       }
    
65.       // We might also just let it drop out of scope
    
66.       toExplode.Clear();
    
67.       // To replicate the explode command, we're delete the
    
68.       // original entity
    
69.       if (erase)
    
70.       {
    
71.         br.UpgradeOpen();
    
72.         br.Erase();
    
73.         br.DowngradeOpen();
    
74.       }
    
75.     }
    
76.   }
    
77. }
    

<br /> using Autodesk.AutoCAD.ApplicationServices;<br /> using Autodesk.AutoCAD.DatabaseServices;<br /> using Autodesk.AutoCAD.EditorInput;<br /> using Autodesk.AutoCAD.Runtime; <br /> namespace Explosions<br /> {<br />   public class Commands<br />   {<br />     [CommandMethod("EB")]<br />     public void ExplodeBock()<br />     {<br />       var doc = Application.DocumentManager.MdiActiveDocument;<br />       if (doc == null)<br />         return;<br />       var ed = doc.Editor;<br />       var db = doc.Database; <br />       // Ask the user to select the block <br />       var peo = new PromptEntityOptions("\nSelect block to explode");<br />       peo.SetRejectMessage("Must be a block.");<br />       peo.AddAllowedClass(typeof(BlockReference), false); <br />       var per = ed.GetEntity(peo); <br />       if (per.Status != PromptStatus.OK)<br />         return; <br />       using (var tr = db.TransactionManager.StartTransaction())<br />       {<br />         // Call our explode function recursively, starting<br />         // with the top-level block reference<br />         // (you can pass false as a 4th parameter if you<br />         // don't want originating entities erased) <br />         ExplodeBlock(tr, db, per.ObjectId);<br />         tr.Commit();<br />       }<br />     } <br />     private void ExplodeBlock(<br />       Transaction tr, Database db, ObjectId id, bool erase = true<br />     )<br />     {<br />       // Open out block reference - only needs to be readable<br />       // for the explode operation, as it's non-destructive<br />       var br = (BlockReference)tr.GetObject(id, OpenMode.ForRead); <br />       // We'll collect the BlockReferences created in a collection <br />       var toExplode = new ObjectIdCollection(); <br />       // Define our handler to capture the nested block references <br />       ObjectEventHandler handler =<br />         (s, e) =><br />         {<br />           if (e.DBObject is BlockReference)<br />           {<br />             toExplode.Add(e.DBObject.ObjectId);<br />           }<br />         }; <br />       // Add our handler around the explode call, removing it<br />       // directly afterwards <br />       db.ObjectAppended += handler;<br />       br.ExplodeToOwnerSpace();<br />       db.ObjectAppended -= handler; <br />       // Go through the results and recurse, exploding the<br />       // contents <br />       foreach (ObjectId bid in toExplode)<br />       {<br />         ExplodeBlock(tr, db, bid, erase);<br />       }<br />       // We might also just let it drop out of scope <br />       toExplode.Clear(); <br />       // To replicate the explode command, we're delete the<br />       // original entity <br />       if (erase)<br />       {<br />         br.UpgradeOpen();<br />         br.Erase();<br />         br.DowngradeOpen();<br />       }<br />     }<br />   }<br /> }<br />