Merge from branch giga

StgSharp.Model/Step/Items/StepElementarySurface.cs

@@ -28,23 +28,24 @@
 //     
 //-----------------------------------------------------------------------
 //-----------------------------------------------------------------------
+using StgSharp.Model.Step;
 using StgSharp.Script;
 using StgSharp.Script.Express;
 
 using System;
 using System.Collections.Generic;
 
-namespace StgSharp.Modeling.Items
+namespace StgSharp.Model.Step
 {
-    public abstract class StepElementarySurface : StepSurface
+    public class StepElementarySurface : StepSurface, IExpConvertableFrom<StepElementarySurface>
     {
 
         private StepAxis2Placement3D _position;
 
-        protected StepElementarySurface() : base( string.Empty ) { }
+        public StepElementarySurface( StepModel model ) : base( model ) { }
 
-        public StepElementarySurface( string name, StepAxis2Placement3D position )
-            : base( name )
+        public StepElementarySurface( StepModel model, StepAxis2Placement3D position )
+            : base( model )
         {
             Position = position;
         }
@@ -54,17 +55,15 @@ namespace StgSharp.Modeling.Items
             get { return _position; }
             set
             {
-                if( value == null ) {
-                    throw new ArgumentNullException();
-                }
-
+                ArgumentNullException.ThrowIfNull( value );
                 _position = value;
             }
         }
 
-        internal override IEnumerable<StepRepresentationItem> GetReferencedItems()
+        public void FromInstance( StepElementarySurface entity )
         {
-            yield return Position;
+            base.FromInstance( entity );
+            _position = entity.Position;
         }
 
     }