AttributeDefinition

Namespace: Autodesk.AutoCAD.DatabaseServices
Assembly: AcDbMgd.dll

Overview

The AttributeDefinition class defines a template for attributes within a block definition. It specifies the tag, prompt, default value, and properties for attributes that will be created when the block is inserted.

Key Concept: AttributeDefinitions exist in block definitions and serve as templates. When a block is inserted, AttributeReferences are created based on these definitions.

Class Hierarchy

Object
  └─ RXObject
      └─ DBObject
          └─ Entity
              └─ DBText
                  └─ AttributeDefinition

Key Properties

Property	Type	Description
`Tag`	`string`	Gets/sets the attribute tag (identifier)
`Prompt`	`string`	Gets/sets the prompt shown when inserting block
`TextString`	`string`	Gets/sets the default value
`Invisible`	`bool`	Gets/sets whether attribute is invisible
`Constant`	`bool`	Gets/sets whether attribute value is constant
`Verifiable`	`bool`	Gets/sets whether to verify value on insertion
`Preset`	`bool`	Gets/sets whether attribute is preset
`LockPositionInBlock`	`bool`	Gets/sets whether position is locked in block
`IsMTextAttributeDefinition`	`bool`	Checks if attribute supports multiline text

Common Usage Patterns

1. Creating Attribute Definition

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Runtime;

[CommandMethod("CREATEATTDEF")]
public void CreateAttributeDefinition()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTable bt = tr.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;
        BlockTableRecord btr = tr.GetObject(bt[BlockTableRecord.ModelSpace], 
            OpenMode.ForWrite) as BlockTableRecord;
        
        // Create attribute definition
        AttributeDefinition attDef = new AttributeDefinition();
        attDef.SetDatabaseDefaults();
        attDef.Position = new Point3d(0, 0, 0);
        attDef.Tag = "PART_NUMBER";
        attDef.Prompt = "Enter part number: ";
        attDef.TextString = "12345";
        attDef.Height = 2.5;
        attDef.Justify = AttachmentPoint.MiddleCenter;
        
        btr.AppendEntity(attDef);
        tr.AddNewlyCreatedDBObject(attDef, true);
        
        tr.Commit();
        doc.Editor.WriteMessage("\nAttribute definition created");
    }
}

2. Creating Block with Attributes

[CommandMethod("CREATEATTBLOCK")]
public void CreateBlockWithAttributes()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    Editor ed = doc.Editor;
    
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTable bt = tr.GetObject(db.BlockTableId, OpenMode.ForWrite) as BlockTable;
        
        // Create new block definition
        BlockTableRecord btr = new BlockTableRecord();
        btr.Name = "TITLE_BLOCK";
        btr.Origin = Point3d.Origin;
        
        ObjectId btrId = bt.Add(btr);
        tr.AddNewlyCreatedDBObject(btr, true);
        
        // Add rectangle to block
        Polyline rect = new Polyline();
        rect.AddVertexAt(0, new Point2d(0, 0), 0, 0, 0);
        rect.AddVertexAt(1, new Point2d(100, 0), 0, 0, 0);
        rect.AddVertexAt(2, new Point2d(100, 50), 0, 0, 0);
        rect.AddVertexAt(3, new Point2d(0, 50), 0, 0, 0);
        rect.Closed = true;
        
        btr.AppendEntity(rect);
        tr.AddNewlyCreatedDBObject(rect, true);
        
        // Add attribute definitions
        AttributeDefinition attDef1 = new AttributeDefinition();
        attDef1.SetDatabaseDefaults();
        attDef1.Position = new Point3d(10, 40, 0);
        attDef1.Tag = "TITLE";
        attDef1.Prompt = "Enter drawing title: ";
        attDef1.TextString = "DRAWING TITLE";
        attDef1.Height = 5.0;
        
        btr.AppendEntity(attDef1);
        tr.AddNewlyCreatedDBObject(attDef1, true);
        
        AttributeDefinition attDef2 = new AttributeDefinition();
        attDef2.SetDatabaseDefaults();
        attDef2.Position = new Point3d(10, 30, 0);
        attDef2.Tag = "DATE";
        attDef2.Prompt = "Enter date: ";
        attDef2.TextString = DateTime.Now.ToShortDateString();
        attDef2.Height = 3.0;
        
        btr.AppendEntity(attDef2);
        tr.AddNewlyCreatedDBObject(attDef2, true);
        
        AttributeDefinition attDef3 = new AttributeDefinition();
        attDef3.SetDatabaseDefaults();
        attDef3.Position = new Point3d(10, 20, 0);
        attDef3.Tag = "DRAWN_BY";
        attDef3.Prompt = "Enter drafter name: ";
        attDef3.TextString = "INITIALS";
        attDef3.Height = 3.0;
        
        btr.AppendEntity(attDef3);
        tr.AddNewlyCreatedDBObject(attDef3, true);
        
        tr.Commit();
        ed.WriteMessage($"\nBlock '{btr.Name}' created with 3 attributes");
    }
}

3. Reading Attribute Definitions from Block

[CommandMethod("LISTATTDEFS")]
public void ListAttributeDefinitions()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    Editor ed = doc.Editor;
    
    // Prompt for block name
    PromptStringOptions pso = new PromptStringOptions("\nEnter block name: ");
    PromptResult pr = ed.GetString(pso);
    if (pr.Status != PromptStatus.OK) return;
    
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTable bt = tr.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;
        
        if (!bt.Has(pr.StringResult))
        {
            ed.WriteMessage($"\nBlock '{pr.StringResult}' not found");
            tr.Commit();
            return;
        }
        
        BlockTableRecord btr = tr.GetObject(bt[pr.StringResult], 
            OpenMode.ForRead) as BlockTableRecord;
        
        ed.WriteMessage($"\n=== Attributes in Block '{btr.Name}' ===");
        
        int count = 0;
        foreach (ObjectId id in btr)
        {
            if (id.ObjectClass.Name == "AcDbAttributeDefinition")
            {
                AttributeDefinition attDef = tr.GetObject(id, 
                    OpenMode.ForRead) as AttributeDefinition;
                
                count++;
                ed.WriteMessage($"\n\nAttribute {count}:");
                ed.WriteMessage($"\n  Tag: {attDef.Tag}");
                ed.WriteMessage($"\n  Prompt: {attDef.Prompt}");
                ed.WriteMessage($"\n  Default: {attDef.TextString}");
                ed.WriteMessage($"\n  Height: {attDef.Height}");
                ed.WriteMessage($"\n  Invisible: {attDef.Invisible}");
                ed.WriteMessage($"\n  Constant: {attDef.Constant}");
            }
        }
        
        if (count == 0)
            ed.WriteMessage("\nNo attributes found in this block");
        
        tr.Commit();
    }
}

4. Modifying Attribute Definitions

[CommandMethod("MODIFYATTDEF")]
public void ModifyAttributeDefinition()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    Editor ed = doc.Editor;
    
    // Select attribute definition
    PromptEntityOptions peo = new PromptEntityOptions("\nSelect attribute definition: ");
    peo.SetRejectMessage("\nMust be an attribute definition.");
    peo.AddAllowedClass(typeof(AttributeDefinition), true);
    
    PromptEntityResult per = ed.GetEntity(peo);
    if (per.Status != PromptStatus.OK) return;
    
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        AttributeDefinition attDef = tr.GetObject(per.ObjectId, 
            OpenMode.ForWrite) as AttributeDefinition;
        
        // Modify properties
        attDef.Prompt = "Updated prompt: ";
        attDef.TextString = "NEW_DEFAULT";
        attDef.Height = 5.0;
        attDef.ColorIndex = 1; // Red
        
        ed.WriteMessage($"\nModified attribute '{attDef.Tag}'");
        
        tr.Commit();
    }
}

5. Creating Invisible and Constant Attributes

[CommandMethod("CREATESPECIALATT")]
public void CreateSpecialAttributes()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTable bt = tr.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;
        BlockTableRecord btr = tr.GetObject(bt[BlockTableRecord.ModelSpace], 
            OpenMode.ForWrite) as BlockTableRecord;
        
        // Invisible attribute (hidden but extractable)
        AttributeDefinition invisibleAtt = new AttributeDefinition();
        invisibleAtt.SetDatabaseDefaults();
        invisibleAtt.Position = new Point3d(0, 0, 0);
        invisibleAtt.Tag = "PART_ID";
        invisibleAtt.TextString = "ABC-123";
        invisibleAtt.Height = 2.5;
        invisibleAtt.Invisible = true; // Won't display but can be extracted
        
        btr.AppendEntity(invisibleAtt);
        tr.AddNewlyCreatedDBObject(invisibleAtt, true);
        
        // Constant attribute (value cannot change)
        AttributeDefinition constantAtt = new AttributeDefinition();
        constantAtt.SetDatabaseDefaults();
        constantAtt.Position = new Point3d(0, 10, 0);
        constantAtt.Tag = "COMPANY";
        constantAtt.TextString = "ACME Corporation";
        constantAtt.Height = 2.5;
        constantAtt.Constant = true; // Value is fixed
        
        btr.AppendEntity(constantAtt);
        tr.AddNewlyCreatedDBObject(constantAtt, true);
        
        tr.Commit();
        doc.Editor.WriteMessage("\nCreated invisible and constant attributes");
    }
}

6. Multiline Text Attribute Definition

[CommandMethod("CREATEMTEXTATT")]
public void CreateMTextAttributeDefinition()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTable bt = tr.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;
        BlockTableRecord btr = tr.GetObject(bt[BlockTableRecord.ModelSpace], 
            OpenMode.ForWrite) as BlockTableRecord;
        
        // Create MText attribute definition
        AttributeDefinition attDef = new AttributeDefinition();
        attDef.SetDatabaseDefaults();
        attDef.Position = new Point3d(0, 0, 0);
        attDef.Tag = "NOTES";
        attDef.Prompt = "Enter notes: ";
        attDef.TextString = "Enter detailed notes here...";
        attDef.Height = 2.5;
        
        // Convert to MText attribute
        attDef.ConvertToMTextAttribute();
        
        btr.AppendEntity(attDef);
        tr.AddNewlyCreatedDBObject(attDef, true);
        
        tr.Commit();
        doc.Editor.WriteMessage("\nMText attribute definition created");
    }
}

Best Practices

Unique Tags: Use unique, descriptive tags (e.g., "PART_NUMBER" not "ATT1")
Clear Prompts: Provide helpful prompts for users
Default Values: Set reasonable defaults
Height: Use consistent text heights
Invisible vs Constant: Use invisible for hidden data, constant for fixed values
Position: Place attributes logically within block geometry
Verification: Use Verifiable flag for critical data

Common Patterns

Pattern 1: Standard Attribute

AttributeDefinition attDef = new AttributeDefinition();
attDef.SetDatabaseDefaults();
attDef.Tag = "TAG_NAME";
attDef.Prompt = "Enter value: ";
attDef.TextString = "DEFAULT";
attDef.Height = 2.5;

Pattern 2: Invisible Data Attribute

attDef.Invisible = true;
attDef.Tag = "DATA_ID";
attDef.TextString = "12345";

Pattern 3: Fixed Value Attribute

attDef.Constant = true;
attDef.Tag = "COMPANY";
attDef.TextString = "Company Name";

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AttributeDefinition

Overview

Class Hierarchy

Key Properties

Common Usage Patterns

1. Creating Attribute Definition

2. Creating Block with Attributes

3. Reading Attribute Definitions from Block

4. Modifying Attribute Definitions

5. Creating Invisible and Constant Attributes

6. Multiline Text Attribute Definition

Best Practices

Common Patterns

Pattern 1: Standard Attribute

Pattern 2: Invisible Data Attribute

Pattern 3: Fixed Value Attribute

Related Classes

See Also

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AttributeDefinition.md

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AttributeDefinition

Overview

Class Hierarchy

Key Properties

Common Usage Patterns

1. Creating Attribute Definition

2. Creating Block with Attributes

3. Reading Attribute Definitions from Block

4. Modifying Attribute Definitions

5. Creating Invisible and Constant Attributes

6. Multiline Text Attribute Definition

Best Practices

Common Patterns

Pattern 1: Standard Attribute

Pattern 2: Invisible Data Attribute

Pattern 3: Fixed Value Attribute

Related Classes

See Also