Topic: Select all instances of a dynamic block

[kaefer]

This topic was recently  at Kean's blog. I do not mean to criticize his approach, which works by generating a selection filter comprising all of the block's names, anonymous or otherwise.

My intent is to demonstrate the use of the SelectionAdded event handler for this problem. Then it's not names, but only an ObjectId which has to be checked for equality.

Code - C#: [Select]

1. // Variation on how to select all instances of a Dynameic block, originally by Kean Walmsley
2. // http://through-the-interface.typepad.com/through_the_interface/2012/09/creating-a-selection-filter-that-finds-dynamic-blocks-in-autocad-using-net.html
3.  
4. using Autodesk.AutoCAD.ApplicationServices;
5. using Autodesk.AutoCAD.Runtime;
6. using Autodesk.AutoCAD.DatabaseServices;
7. using Autodesk.AutoCAD.EditorInput;
8. using System.Collections.Generic;
9.  
10. namespace EntitySelection
11. {
12.     public class Commands
13.     {
14.         [CommandMethod("SDB")]
15.         static public void SelectDynamicBlocks()
16.         {
17.             var doc = Application.DocumentManager.MdiActiveDocument;
18.             var ed = doc.Editor;
19.  
20.             var pso =
21.               new PromptStringOptions(
22.                 "\nName of dynamic block to search for"
23.               );
24.             pso.AllowSpaces = true;
25.  
26.             var pr = ed.GetString(pso);
27.  
28.             if (pr.Status != PromptStatus.OK)
29.                 return;
30.  
31.             string blkName = pr.StringResult;
32.  
33.             List<string> blkNames = new List<string>();
34.             blkNames.Add(blkName);
35.  
36.             PromptSelectionResult psr;
37.             using (var tr = doc.TransactionManager.StartTransaction())
38.             {
39.                 var bt =
40.                   (BlockTable)tr.GetObject(
41.                     doc.Database.BlockTableId,
42.                     OpenMode.ForRead
43.                   );
44.  
45.                 // Start by getting access to our block, if it exists
46.  
47.                 if (!bt.Has(blkName))
48.                 {
49.                     ed.WriteMessage(
50.                       "\nCannot find block called \"{0}\".", blkName
51.                     );
52.                     return;
53.                 }
54.  
55.                 // Skip the test for IsDynamicBlock, since this will work
56.                 // for standard blocks regardless
57.  
58.                 // Define an event handler in the current scope
59.  
60.                 SelectionAddedEventHandler handler =
61.                     delegate(object sender, SelectionAddedEventArgs e)
62.                     {
63.                         foreach (int i in e.AddedObjects.GetIndicesToRemove(bt[blkName]))
64.                             e.Remove(i);
65.                     };
66.  
67.                 // Select anonymous "`**" and regular "*" block references
68.  
69.                 SelectionFilter sf =
70.                     new SelectionFilter(new TypedValue[] {
71.                         new TypedValue(
72.                             (int)DxfCode.BlockName, "`**,*")});
73.  
74.                 ed.SelectionAdded += handler;
75.                 try
76.                 {
77.                     psr = ed.SelectAll(sf);
78.                 }
79.                 finally
80.                 {
81.                     ed.SelectionAdded -= handler;
82.                 }
83.                 tr.Commit();
84.             }
85.  
86.             if (psr == null || psr.Value == null)
87.             {
88.                 ed.WriteMessage("\nNo entities found. ");
89.                 return;
90.             }
91.             ed.WriteMessage(
92.               "\nFound {0} entit{1}.",
93.               psr.Value.Count,
94.               (psr.Value.Count == 1 ? "y" : "ies")
95.             );
96.         }
97.     }
98.     static class IEnumerable
99.     {
100.         // Extension to SelectionSet which opens all block references that pass
101.         // the SelectionFilter. Returns a sequence of integer indices corresponding
102.         // to the block's position in the SelectionSet, which will remove them from it.
103.         // Don't return any index for a block refences whose DynamicBlockTableRecord
104.         // property isn't equal to the ObjectId of our wanted block's prototype definition
105.  
106.         public static IEnumerable<int> GetIndicesToRemove(this SelectionSet added, ObjectId btrOid)
107.         {
108.             int i = 0;
109.             foreach (SelectedObject so in added)
110.             {
111.                 var br =
112.                     (BlockReference)so.ObjectId.GetObject(OpenMode.ForRead);
113.                 if (br.DynamicBlockTableRecord != btrOid)
114.                     yield return i;
115.                 i++;
116.             }
117.         }
118.     }
119. }
120.