LayerTable.md

LayerTable Class

Overview

The LayerTable class is a symbol table that contains all layer definitions in an AutoCAD drawing.

Namespace

Autodesk.AutoCAD.DatabaseServices

Inheritance Hierarchy

System.Object
  └─ RXObject
      └─ DBObject
          └─ SymbolTable
              └─ LayerTable

Key Methods

Method	Return Type	Description
Has(string)	bool	Checks if a layer exists by name
this[string]	ObjectId	Gets layer ObjectId by name (indexer)

Code Examples

Example 1: Listing All Layers

using (Transaction tr = db.TransactionManager.StartTransaction())
{
    LayerTable lt = tr.GetObject(db.LayerTableId, OpenMode.ForRead) as LayerTable;
    
    ed.WriteMessage("\nLayers in drawing:");
    
    foreach (ObjectId layerId in lt)
    {
        LayerTableRecord ltr = tr.GetObject(layerId, OpenMode.ForRead) as LayerTableRecord;
        
        ed.WriteMessage($"\n  {ltr.Name}");
        ed.WriteMessage($" - Color: {ltr.Color.ColorIndex}");
        ed.WriteMessage($" - {(ltr.IsFrozen ? "Frozen" : "Thawed")}");
        ed.WriteMessage($" - {(ltr.IsOff ? "Off" : "On")}");
        ed.WriteMessage($" - {(ltr.IsLocked ? "Locked" : "Unlocked")}");
    }
    
    tr.Commit();
}

Example 2: Creating a New Layer

using (Transaction tr = db.TransactionManager.StartTransaction())
{
    LayerTable lt = tr.GetObject(db.LayerTableId, OpenMode.ForWrite) as LayerTable;
    
    if (!lt.Has("MyLayer"))
    {
        LayerTableRecord ltr = new LayerTableRecord();
        ltr.Name = "MyLayer";
        ltr.Color = Color.FromColorIndex(ColorMethod.ByAci, 1); // Red
        
        lt.Add(ltr);
        tr.AddNewlyCreatedDBObject(ltr, true);
        
        ed.WriteMessage("\nLayer 'MyLayer' created");
    }
    
    tr.Commit();
}

Example 3: Modifying Layer Properties

using (Transaction tr = db.TransactionManager.StartTransaction())
{
    LayerTable lt = tr.GetObject(db.LayerTableId, OpenMode.ForRead) as LayerTable;
    
    if (lt.Has("MyLayer"))
    {
        LayerTableRecord ltr = tr.GetObject(lt["MyLayer"], OpenMode.ForWrite) as LayerTableRecord;
        
        ltr.Color = Color.FromColorIndex(ColorMethod.ByAci, 3); // Green
        ltr.IsFrozen = false;
        ltr.IsOff = false;
        ltr.IsLocked = false;
    }
    
    tr.Commit();
}

Related Objects

• Database - Contains LayerTableId
• Entity - Entities have Layer property
• LayerTableRecord - Layer definition

References

• Autodesk Official Documentation