Topic: Using Hard pointers to manage layers

[sovby]

I have a user at my office who purges Autocad drawings with layers that i want to keep in the drawings. Someone in the Augi forum suggested using hard pointers to keep the layers from being removed. Has anyone done anything similar to this? I do not have much experience using xrecords. Here is a sample from the forum post. "A hard pointer should prevent the pointed-to object (layer, in this case) from being purged. The pointer would reside under an XRecord in an Extension Dictionary, possibly attached to the Layers collection or the drawings named object dictionary." Would this work & if so how would i go about doing this?

[gile]

Hi,

You can try these extension methods I wrote some time ago.

Code - C#: [Select]

1.     public static class Extensions
2.     {
3.         // Opens the object for read.
4.         public static T GetObject<T>(this ObjectId id) where T : DBObject
5.         {
6.             return (T)id.GetObject(OpenMode.ForRead, false, false);
7.         }
8.  
9.         // Opens the object in the specified mode
10.         public static T GetObject<T>(this ObjectId id, OpenMode mode) where T : DBObject
11.         {
12.             return (T)id.GetObject(mode, false, false);
13.         }
14.  
15.         // Gets the object extension dictionary (returns null if not found)
16.         public static DBDictionary GetExtensionDictionary(this DBObject obj)
17.         {
18.             ObjectId dictId = obj.ExtensionDictionary;
19.             if (dictId == ObjectId.Null)
20.             {
21.                 return null;
22.             }
23.             return dictId.GetObject<DBDictionary>();
24.         }
25.  
26.         // Gets the object extension dictionary (creates it if not already exists)
27.         public static DBDictionary GetOrCreateExtensionDictionary(this DBObject obj)
28.         {
29.             if (obj.ExtensionDictionary == ObjectId.Null)
30.             {
31.                 obj.UpgradeOpen();
32.                 obj.CreateExtensionDictionary();
33.             }
34.             return obj.ExtensionDictionary.GetObject<DBDictionary>();
35.         }
36.  
37.         // Gets the xrecord data
38.         public static ResultBuffer GetXrecordData(this DBDictionary dict, string key)
39.         {
40.             if (!dict.Contains(key)) return null;
41.             ObjectId id = (ObjectId)dict[key];
42.             if (id.ObjectClass != RXObject.GetClass(typeof(Xrecord))) return null;
43.             return id.GetObject<Xrecord>().Data;
44.         }
45.  
46.         // Sets the xrecord data
47.         public static void SetXrecordData(this DBDictionary dict, string key, ResultBuffer data)
48.         {
49.             Xrecord xrec;
50.             if (dict.Contains(key))
51.             {
52.                 xrec = ((ObjectId)dict[key]).GetObject<Xrecord>(OpenMode.ForWrite);
53.             }
54.             else
55.             {
56.                 dict.UpgradeOpen();
57.                 xrec = new Xrecord();
58.                 dict.SetAt(key, xrec);
59.                 dict.Database.TransactionManager.TopTransaction.AddNewlyCreatedDBObject(xrec, true);
60.             }
61.             xrec.Data = data;
62.         }
63.  
64.         // Sets the symbol table record unpurgeable by referencing it in its symbol table extension dictionary
65.         public static void SetUnpurgeable(this SymbolTableRecord str)
66.         {
67.             SymbolTable st = str.OwnerId.GetObject<SymbolTable>();
68.             DBDictionary xdict = st.GetOrCreateExtensionDictionary();
69.             ResultBuffer data = xdict.GetXrecordData("GILE_UNPURGE") ?? new ResultBuffer();
70.             data.Add(new TypedValue(340, str.ObjectId));
71.             xdict.SetXrecordData("GILE_UNPURGE", data);
72.         }
73.  
74.         // Resets the symbol table record purgeable by unreferencing it in its symbol table extension dictionary
75.         public static void ResetPurgeable(this SymbolTableRecord str)
76.         {
77.             SymbolTable st = str.OwnerId.GetObject<SymbolTable>();
78.             DBDictionary xdict = st.GetExtensionDictionary();
79.             if (xdict == null) return;
80.             ResultBuffer data = xdict.GetXrecordData("GILE_UNPURGE");
81.             if (data == null) return;
82.             var values = data.AsArray()
83.                 .Where(tv => tv.TypeCode != 340 || (ObjectId)tv.Value != st.ObjectId)
84.                 .ToArray();
85.             xdict.SetXrecordData("GILE_UNPURGE", new ResultBuffer(values));
86.         }
87.     }

Using example, adds a new layer named "unpurgeable" to the layer table and set it 'unpurgeable':

Code - C#: [Select]

1.             using (Transaction tr = db.TransactionManager.StartTransaction())
2.             {
3.                 LayerTable lt = db.LayerTableId.GetObject<LayerTable>(OpenMode.ForWrite);
4.                 LayerTableRecord ltr = new LayerTableRecord();
5.                 ltr.Name = "unpurgeable";
6.                 lt.Add(ltr);
7.                 tr.AddNewlyCreatedDBObject(ltr, true);
8.                 ltr.SetUnpurgeable();
9.                 tr.Commit();
10.             }

[sovby]

Sorry for my lack of knowledge on this but do i combine these two together & add my specific layers in. There's roughly 300 of them. Also how would i implement this? Do i need to compile this & turn it into a dll file or something?

[gile]

Extension methods are used to add methods to a predefined type (see this page).

If you add the upper "Extensions" class to your project, those method will be available for the extended type (for your purpose, the SetUnpurgeable() method extents the SymbolTableRecord abstract type which LayerTableRecord derived from).
So, in you code, open each LayerTableRecord instance you want to set unpurgeable and call the SetUnpurgeable method on it.

[MexicanCustard]

Gile, why wrap ObjectId.GetObject() with a GetObject method?  I think it was Tony T that pointed out the inefficiencies of ObjectId.GetObject().  Just asking, since I know you'll have a good reason.

[gile]

Hi,

This is an old (short) version.

Here's the one I use now:

Code - C#: [Select]

1.         public static T GetObject<T>(
2.             this ObjectId id,
3.             OpenMode mode = OpenMode.ForRead,
4.             bool openErased = false,
5.             bool forceOpenOnLockedLayer = false)
6.             where T : DBObject
7.         {
8.             if (id == ObjectId.Null)
9.                 throw new ArgumentException("The value cannot be ObjectId.Null.", "id");
10.  
11.             Transaction tr = id.Database.TransactionManager.TopTransaction;
12.             if (tr == null)
13.                 throw new AcRx.Exception(ErrorStatus.NoActiveTransactions);
14.  
15.             return (T)tr.GetObject(id, mode, openErased, forceOpenOnLockedLayer);
16.         }

Anyway, even if ObjectId.GetObject() is (a little) less efficient than Transaction.GetOject() (which is less efficient than OpenCloseTransaction.GetObject() or ObjectId.Open()), the goal here was more to get a succint and readable code.

[MexicanCustard]

Anyway, even if ObjectId.GetObject() is (a little) less efficient than Transaction.GetOject() (which is less efficient than OpenCloseTransaction.GetObject() or ObjectId.Open()), the goal here was more to get a succint and readable code.

Just to be clear, I wasn't picking holes in your code.  I understand you were just showing the OP an example.  I thought maybe you knew something I didn't, since your knowledge of the API is better than mine.  Thank you for clarifying though.

[gile]

since your knowledge of the API is better than mine.

I'm thinking the same about you.

[sovby]

Extension methods are used to add methods to a predefined type (see this page).

If you add the upper "Extensions" class to your project, those method will be available for the extended type (for your purpose, the SetUnpurgeable() method extents the SymbolTableRecord abstract type which LayerTableRecord derived from).
So, in you code, open each LayerTableRecord instance you want to set unpurgeable and call the SetUnpurgeable method on it.

Sorry i'm such a dummy on this but if i understand you correctly i need to add all my layers into this code like layer1,layer2,layer3,etc. Also i am not sure how to implement this. Do i compile this into a dll file? This is my template file. i want all of these layers to be unpurgeable. Do i need to run this code in side of this file?

[mjfarrell]

might it not be easier to tell people to STOP purging layers?

and or

frustrate the bugger....place a single autocad point on those layers...then he can't purge them...pdmode=1

they wont even be able to see them....

[gile]

sovby,

Yes, you can compile the extension class in a dll, this is a good way to build a re-usable library, but in this case it will be a very small library...

You can also, as I said, just add this class to the project which use it, even in a separate file or in the same file as the command method which use it as shown in the following example.

Code - C#: [Select]

1. using Autodesk.AutoCAD.ApplicationServices;
2. using Autodesk.AutoCAD.DatabaseServices;
3. using Autodesk.AutoCAD.EditorInput;
4. using Autodesk.AutoCAD.Runtime;
5. using System.Linq;
6. using AcAp = Autodesk.AutoCAD.ApplicationServices.Application;
7.  
8. [assembly: CommandClass(typeof(SetAllLayersUnpurgeable.Commands))]
9.  
10. namespace SetAllLayersUnpurgeable
11. {
12.     public class Commands
13.     {
14.         [CommandMethod("Cmd")]
15.         public void SetAllLayersUnpurgeableCmd()
16.         {
17.             var db = HostApplicationServices.WorkingDatabase;
18.             using (var tr = db.TransactionManager.StartTransaction())
19.             {
20.                 var layerTable = db.LayerTableId.GetObject<LayerTable>();
21.                 foreach (ObjectId layerId in layerTable)
22.                 {
23.                     if (layerId != db.LayerZero)
24.                     {
25.                         layerId.GetObject<LayerTableRecord>().SetUnpurgeable();
26.                     }
27.                 }
28.                 tr.Commit();
29.             }
30.         }
31.     }
32.  
33.     public static class Extensions
34.     {
35.         // Opens the object for read.
36.         public static T GetObject<T>(this ObjectId id) where T : DBObject
37.         {
38.             return (T)id.GetObject(OpenMode.ForRead, false, false);
39.         }
40.  
41.         // Opens the object in the specified mode
42.         public static T GetObject<T>(this ObjectId id, OpenMode mode) where T : DBObject
43.         {
44.             return (T)id.GetObject(mode, false, false);
45.         }
46.  
47.         // Gets the object extension dictionary (returns null if not found)
48.         public static DBDictionary GetExtensionDictionary(this DBObject obj)
49.         {
50.             ObjectId dictId = obj.ExtensionDictionary;
51.             if (dictId == ObjectId.Null)
52.             {
53.                 return null;
54.             }
55.             return dictId.GetObject<DBDictionary>();
56.         }
57.  
58.         // Gets the object extension dictionary (creates it if not already exists)
59.         public static DBDictionary GetOrCreateExtensionDictionary(this DBObject obj)
60.         {
61.             if (obj.ExtensionDictionary == ObjectId.Null)
62.             {
63.                 obj.UpgradeOpen();
64.                 obj.CreateExtensionDictionary();
65.             }
66.             return obj.ExtensionDictionary.GetObject<DBDictionary>();
67.         }
68.  
69.         // Gets the xrecord data
70.         public static ResultBuffer GetXrecordData(this DBDictionary dict, string key)
71.         {
72.             if (!dict.Contains(key)) return null;
73.             ObjectId id = (ObjectId)dict[key];
74.             if (id.ObjectClass != RXObject.GetClass(typeof(Xrecord))) return null;
75.             return id.GetObject<Xrecord>().Data;
76.         }
77.  
78.         // Sets the xrecord data
79.         public static void SetXrecordData(this DBDictionary dict, string key, ResultBuffer data)
80.         {
81.             Xrecord xrec;
82.             if (dict.Contains(key))
83.             {
84.                 xrec = ((ObjectId)dict[key]).GetObject<Xrecord>(OpenMode.ForWrite);
85.             }
86.             else
87.             {
88.                 dict.UpgradeOpen();
89.                 xrec = new Xrecord();
90.                 dict.SetAt(key, xrec);
91.                 dict.Database.TransactionManager.TopTransaction.AddNewlyCreatedDBObject(xrec, true);
92.             }
93.             xrec.Data = data;
94.         }
95.  
96.         // Sets the symbol table record unpurgeable by referencing it in its symbol table extension dictionary
97.         public static void SetUnpurgeable(this SymbolTableRecord str)
98.         {
99.             SymbolTable st = str.OwnerId.GetObject<SymbolTable>();
100.             DBDictionary xdict = st.GetOrCreateExtensionDictionary();
101.             ResultBuffer data = xdict.GetXrecordData("GILE_UNPURGE") ?? new ResultBuffer();
102.             data.Add(new TypedValue(340, str.ObjectId));
103.             xdict.SetXrecordData("GILE_UNPURGE", data);
104.         }
105.  
106.         // Resets the symbol table record purgeable by unreferencing it in its symbol table extension dictionary
107.         public static void ResetPurgeable(this SymbolTableRecord str)
108.         {
109.             SymbolTable st = str.OwnerId.GetObject<SymbolTable>();
110.             DBDictionary xdict = st.GetExtensionDictionary();
111.             if (xdict == null) return;
112.             ResultBuffer data = xdict.GetXrecordData("GILE_UNPURGE");
113.             if (data == null) return;
114.             var values = data.AsArray()
115.                 .Where(tv => tv.TypeCode != 340 || (ObjectId)tv.Value != st.ObjectId)
116.                 .ToArray();
117.             xdict.SetXrecordData("GILE_UNPURGE", new ResultBuffer(values));
118.         }
119.     }
120. }
121.  

mjfarrell,

frustrate the bugger....place a single autocad point on those layers...then he can't purge them...pdmode=1

This is what sovby did in the attached file. Anyone can set PDMODE to 3 (or whatever else to display the points), erase the points (within a block reference here) and purge all.

[dgorsman]

Well yeah, its always easier to tell them the right way.  They bob their head and reply "Yes.  Yes.  Yes." and promptly go back to doing what they think is right.

There can be other, non-user related complications.  We have some tools from one client which automatically purges everything every time a drawing is opened.

[Jeff H]

Similar idea discussed here.https://www.theswamp.org/index.php?topic=41870.msg469849#msg469849

[sovby]

might it not be easier to tell people to STOP purging layers?

and or

frustrate the bugger....place a single autocad point on those layers...then he can't purge them...pdmode=1

they wont even be able to see them....

Yeah it would be but in my case i don't think it would work. My solution was to create a block with points on every layer which i made small & put it in the bottom left corner but they found it & deleted the block. I guess i didn't hide it well enough.

[sovby]

sovby,

Yes, you can compile the extension class in a dll, this is a good way to build a re-usable library, but in this case it will be a very small library...

You can also, as I said, just add this class to the project which use it, even in a separate file or in the same file as the command method which use it as shown in the following example.

Code - C#: [Select]

1. using Autodesk.AutoCAD.ApplicationServices;
2. using Autodesk.AutoCAD.DatabaseServices;
3. using Autodesk.AutoCAD.EditorInput;
4. using Autodesk.AutoCAD.Runtime;
5. using System.Linq;
6. using AcAp = Autodesk.AutoCAD.ApplicationServices.Application;
7.  
8. [assembly: CommandClass(typeof(SetAllLayersUnpurgeable.Commands))]
9.  
10. namespace SetAllLayersUnpurgeable
11. {
12.     public class Commands
13.     {
14.         [CommandMethod("Cmd")]
15.         public void SetAllLayersUnpurgeableCmd()
16.         {
17.             var db = HostApplicationServices.WorkingDatabase;
18.             using (var tr = db.TransactionManager.StartTransaction())
19.             {
20.                 var layerTable = db.LayerTableId.GetObject<LayerTable>();
21.                 foreach (ObjectId layerId in layerTable)
22.                 {
23.                     if (layerId != db.LayerZero)
24.                     {
25.                         layerId.GetObject<LayerTableRecord>().SetUnpurgeable();
26.                     }
27.                 }
28.                 tr.Commit();
29.             }
30.         }
31.     }
32.  
33.     public static class Extensions
34.     {
35.         // Opens the object for read.
36.         public static T GetObject<T>(this ObjectId id) where T : DBObject
37.         {
38.             return (T)id.GetObject(OpenMode.ForRead, false, false);
39.         }
40.  
41.         // Opens the object in the specified mode
42.         public static T GetObject<T>(this ObjectId id, OpenMode mode) where T : DBObject
43.         {
44.             return (T)id.GetObject(mode, false, false);
45.         }
46.  
47.         // Gets the object extension dictionary (returns null if not found)
48.         public static DBDictionary GetExtensionDictionary(this DBObject obj)
49.         {
50.             ObjectId dictId = obj.ExtensionDictionary;
51.             if (dictId == ObjectId.Null)
52.             {
53.                 return null;
54.             }
55.             return dictId.GetObject<DBDictionary>();
56.         }
57.  
58.         // Gets the object extension dictionary (creates it if not already exists)
59.         public static DBDictionary GetOrCreateExtensionDictionary(this DBObject obj)
60.         {
61.             if (obj.ExtensionDictionary == ObjectId.Null)
62.             {
63.                 obj.UpgradeOpen();
64.                 obj.CreateExtensionDictionary();
65.             }
66.             return obj.ExtensionDictionary.GetObject<DBDictionary>();
67.         }
68.  
69.         // Gets the xrecord data
70.         public static ResultBuffer GetXrecordData(this DBDictionary dict, string key)
71.         {
72.             if (!dict.Contains(key)) return null;
73.             ObjectId id = (ObjectId)dict[key];
74.             if (id.ObjectClass != RXObject.GetClass(typeof(Xrecord))) return null;
75.             return id.GetObject<Xrecord>().Data;
76.         }
77.  
78.         // Sets the xrecord data
79.         public static void SetXrecordData(this DBDictionary dict, string key, ResultBuffer data)
80.         {
81.             Xrecord xrec;
82.             if (dict.Contains(key))
83.             {
84.                 xrec = ((ObjectId)dict[key]).GetObject<Xrecord>(OpenMode.ForWrite);
85.             }
86.             else
87.             {
88.                 dict.UpgradeOpen();
89.                 xrec = new Xrecord();
90.                 dict.SetAt(key, xrec);
91.                 dict.Database.TransactionManager.TopTransaction.AddNewlyCreatedDBObject(xrec, true);
92.             }
93.             xrec.Data = data;
94.         }
95.  
96.         // Sets the symbol table record unpurgeable by referencing it in its symbol table extension dictionary
97.         public static void SetUnpurgeable(this SymbolTableRecord str)
98.         {
99.             SymbolTable st = str.OwnerId.GetObject<SymbolTable>();
100.             DBDictionary xdict = st.GetOrCreateExtensionDictionary();
101.             ResultBuffer data = xdict.GetXrecordData("GILE_UNPURGE") ?? new ResultBuffer();
102.             data.Add(new TypedValue(340, str.ObjectId));
103.             xdict.SetXrecordData("GILE_UNPURGE", data);
104.         }
105.  
106.         // Resets the symbol table record purgeable by unreferencing it in its symbol table extension dictionary
107.         public static void ResetPurgeable(this SymbolTableRecord str)
108.         {
109.             SymbolTable st = str.OwnerId.GetObject<SymbolTable>();
110.             DBDictionary xdict = st.GetExtensionDictionary();
111.             if (xdict == null) return;
112.             ResultBuffer data = xdict.GetXrecordData("GILE_UNPURGE");
113.             if (data == null) return;
114.             var values = data.AsArray()
115.                 .Where(tv => tv.TypeCode != 340 || (ObjectId)tv.Value != st.ObjectId)
116.                 .ToArray();
117.             xdict.SetXrecordData("GILE_UNPURGE", new ResultBuffer(values));
118.         }
119.     }
120. }
121.  

mjfarrell,

frustrate the bugger....place a single autocad point on those layers...then he can't purge them...pdmode=1

This is what sovby did in the attached file. Anyone can set PDMODE to 3 (or whatever else to display the points), erase the points (within a block reference here) and purge all.

I really apologize for asking this but i feel like i might need step by step directions for this. I have visual studio so would i use that to copy this code into or just notepad? What kind of file would i save it to? How do i get it to talk with Autocad? Again, i am very sorry but i have never done any thing like this before with Autocad. I have gotten a little bit more familiar with c# language but i am lost as to what the procedure would be to make this happen. Does this look at the file that i posted to get the layers or do i have to add them all in manually into this code? If so where exactly do i need to do this? You said to add the class to the projects that use it but i dont know what you mean. How do i do this?