參考：Hatch with transparency - Autodesk Community - AutoCAD

實體有一個Transparency的屬性。

核心程式碼：

  　　　 [CommandMethod("TestTransparencyHatch", CommandFlags.Modal)]
        public void TransparencyHatch() 
        {
            Database db = HostApplicationServices.WorkingDatabase;                   
            
 
using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                BlockTable bt = tr.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;               
                BlockTableRecord btr = bt[BlockTableRecord.ModelSpace].GetObject(OpenMode.ForRead) as BlockTableRecord;
                    
 
foreach (ObjectId btrObjId in btr)
                    {
                        Entity ent = btrObjId.GetObject(OpenMode.ForRead) as Entity;
                        if (ent is Hatch)
                        {
                            ent.UpgradeOpen();
                            Autodesk.AutoCAD.Colors.Transparency trpy 
 
= new Autodesk.AutoCAD.Colors.Transparency(40);
                            ent.Transparency = trpy;                    
                        }         
                }
                tr.Commit();
            }           
        }