Fix for GitHub Issue 142

Author: juileetikekar

src/AasxCsharpLibrary/Extensions/ExtendEnvironment.cs

@@ -748,11 +748,24 @@ public static IReferable FindReferableByReference(
                     }
             }
 
+            
+
             if (firstKeyType.IsSME() && submodelElems != null)
             {
-                var submodelElement = submodelElems.Where(
+                ISubmodelElement submodelElement;
+                //check if key.value is index 
+                bool isIndex = int.TryParse(firstKeyId, out int index);
+                if (isIndex)
+                {
+                    var smeList = submodelElems.ToList();
+                    submodelElement = smeList[index];
+                }
+                else
+                {
+                    submodelElement = submodelElems.Where(
                     sme => sme.IdShort.Equals(keyList[keyIndex].Value,
                         StringComparison.OrdinalIgnoreCase)).First();
+                }
 
                 //This is required element
                 if (keyIndex + 1 >= keyList.Count)

src/AasxPackageLogic/VisualAasxElements.cs

@@ -406,9 +406,17 @@ public VisualElementGeneric FindSibling(bool before = true, bool after = true)
                 if (ve.GetMainDataObject() is Aas.IReferable rf)
                 {
                     // add a key and go up ..
-                    res.Insert(
-                        0,
-                        new Aas.Key((Aas.KeyTypes)Aas.Stringification.KeyTypesFromString(rf.GetSelfDescription().AasElementName), rf.IdShort));
+                    IKey key;
+                    if (ve.Parent.GetMainDataObject() is ISubmodelElementList smeList)
+                    {
+                        var index = smeList.Value.IndexOf((ISubmodelElement)rf);
+                        key = new Aas.Key((Aas.KeyTypes)Aas.Stringification.KeyTypesFromString(rf.GetSelfDescription().AasElementName), index.ToString());
+                    }
+                    else
+                    {
+                        key = new Aas.Key((Aas.KeyTypes)Aas.Stringification.KeyTypesFromString(rf.GetSelfDescription().AasElementName), rf.IdShort);
+                    }
+                    res.Insert(0,key);
                 }
                 else
                 // uups!