diff --git a/src/App/ExtensionContainer.h b/src/App/ExtensionContainer.h
index 258e13528..1eeb09d00 100644
--- a/src/App/ExtensionContainer.h
+++ b/src/App/ExtensionContainer.h
@@ -120,10 +120,12 @@ public:
     virtual ~ExtensionContainer();
 
     void registerExtension(Base::Type extension, App::Extension* ext);
-    bool hasExtension(Base::Type) const;
+    bool hasExtension(Base::Type) const; //returns first of type (or derived from) and throws otherwise
     bool hasExtension(const char* name) const; //this version does not check derived classes
-    App::Extension* getExtension(Base::Type);
+    App::Extension* getExtension(Base::Type);  //returns first of type (or derived from) and throws otherwise
     App::Extension* getExtension(const char* name); //this version does not check derived classes
+    
+    //returns first of type (or derived from) and throws otherwise
     template<typename ExtensionT>
     ExtensionT* getExtensionByType() {
         return dynamic_cast<ExtensionT*>(getExtension(ExtensionT::getClassTypeId()));
diff --git a/src/Gui/Application.cpp b/src/Gui/Application.cpp
index 1621b380a..da5caa8c8 100644
--- a/src/Gui/Application.cpp
+++ b/src/Gui/Application.cpp
@@ -1473,6 +1473,7 @@ void Application::initTypes(void)
     Gui::ViewProvider                           ::init();
     Gui::ViewProviderExtension                  ::init();
     Gui::ViewProviderGroupExtension             ::init();
+    Gui::ViewProviderGeoFeatureGroupExtension   ::init();
     Gui::ViewProviderExtern                     ::init();
     Gui::ViewProviderDocumentObject             ::init();
     Gui::ViewProviderFeature                    ::init();
diff --git a/src/Gui/CMakeLists.txt b/src/Gui/CMakeLists.txt
index c106295df..ab332f309 100644
--- a/src/Gui/CMakeLists.txt
+++ b/src/Gui/CMakeLists.txt
@@ -823,6 +823,7 @@ SET(Viewprovider_CPP_SRCS
     ViewProvider.cpp
     ViewProviderExtension.cpp
     ViewProviderGroupExtension.cpp
+    ViewProviderGeoFeatureGroupExtension.cpp
     ViewProviderAnnotation.cpp
     ViewProviderDocumentObject.cpp
     ViewProviderDocumentObjectGroup.cpp
@@ -852,6 +853,7 @@ SET(Viewprovider_SRCS
     ViewProvider.h
     ViewProviderExtension.h
     ViewProviderGroupExtension.h
+    ViewProviderGeoFeatureGroupExtension.h
     ViewProviderAnnotation.h
     ViewProviderDocumentObject.h
     ViewProviderDocumentObjectGroup.h
diff --git a/src/Gui/ViewProvider.cpp b/src/Gui/ViewProvider.cpp
index 56c655d7f..01496d7c1 100644
--- a/src/Gui/ViewProvider.cpp
+++ b/src/Gui/ViewProvider.cpp
@@ -306,8 +306,30 @@ std::vector<std::string> ViewProvider::getDisplayMaskModes() const
 void ViewProvider::setDisplayMode(const char* ModeName)
 {
     _sCurrentMode = ModeName;
+    
+    //infom the exteensions
+    auto vector = getExtensionsDerivedFromType<Gui::ViewProviderExtension>();
+    for(Gui::ViewProviderExtension* ext : vector)
+        ext->extensionSetDisplayMode(ModeName);
 }
 
+const char* ViewProvider::getDefaultDisplayMode() const {
+
+    return 0;
+}
+
+vector<std::string> ViewProvider::getDisplayModes(void) const {
+
+    std::vector< std::string > modes;
+    auto vector = getExtensionsDerivedFromType<Gui::ViewProviderExtension>();
+    for(Gui::ViewProviderExtension* ext : vector) {
+        auto extModes = ext->extensionGetDisplayModes();
+        modes.insert( modes.end(), extModes.begin(), extModes.end() );
+    }
+    return modes;
+}
+
+
 std::string ViewProvider::getActiveDisplayMode(void) const
 {
     return _sCurrentMode;
@@ -593,4 +615,44 @@ void ViewProvider::Restore(Base::XMLReader& reader) {
     auto vector = getExtensionsDerivedFromType<Gui::ViewProviderExtension>();
     for(Gui::ViewProviderExtension* ext : vector)
         ext->extensionRestore(reader);
-}
\ No newline at end of file
+}
+
+void ViewProvider::updateData(const App::Property* prop) {
+
+    auto vector = getExtensionsDerivedFromType<Gui::ViewProviderExtension>();
+    for(Gui::ViewProviderExtension* ext : vector)
+        ext->extensionUpdateData(prop);
+}
+
+SoSeparator* ViewProvider::getBackRoot(void) const {
+
+    auto vector = getExtensionsDerivedFromType<Gui::ViewProviderExtension>();
+    for(Gui::ViewProviderExtension* ext : vector) {
+        auto* node = ext->extensionGetBackRoot();
+        if(node)
+            return node;
+    }
+    return nullptr;
+}
+
+SoGroup* ViewProvider::getChildRoot(void) const {
+
+    auto vector = getExtensionsDerivedFromType<Gui::ViewProviderExtension>();
+    for(Gui::ViewProviderExtension* ext : vector) {
+        auto* node = ext->extensionGetChildRoot();
+        if(node)
+            return node;
+    }
+    return nullptr;
+}
+
+SoSeparator* ViewProvider::getFrontRoot(void) const {
+
+    auto vector = getExtensionsDerivedFromType<Gui::ViewProviderExtension>();
+    for(Gui::ViewProviderExtension* ext : vector) {
+        auto* node = ext->extensionGetFrontRoot();
+        if(node)
+            return node;
+    }
+    return nullptr;
+}
diff --git a/src/Gui/ViewProvider.h b/src/Gui/ViewProvider.h
index a68f10991..7b54a2757 100644
--- a/src/Gui/ViewProvider.h
+++ b/src/Gui/ViewProvider.h
@@ -99,11 +99,11 @@ public:
     // returns the root for the Annotations. 
     SoSeparator* getAnnotation(void);
     // returns the root node of the Provider (3D)
-    virtual SoSeparator* getFrontRoot(void) const {return 0;}
+    virtual SoSeparator* getFrontRoot(void) const;
     // returns the root node where the children gets collected(3D)
-    virtual SoGroup* getChildRoot(void) const {return 0;}
+    virtual SoGroup* getChildRoot(void) const;
     // returns the root node of the Provider (3D)
-    virtual SoSeparator* getBackRoot(void) const {return 0;}
+    virtual SoSeparator* getBackRoot(void) const;
     /** deliver the children belonging to this object
       * this method is used to deliver the objects to 
       * the 3DView which should be grouped under its 
@@ -208,7 +208,7 @@ public:
      * the data has manipulated.
      */
     void update(const App::Property*);
-    virtual void updateData(const App::Property*)=0;
+    virtual void updateData(const App::Property*);
     bool isUpdatesEnabled () const;
     void setUpdatesEnabled (bool enable);
 
@@ -227,9 +227,9 @@ public:
     /// set the display mode
     virtual void setDisplayMode(const char* ModeName);
     /// get the default display mode
-    virtual const char* getDefaultDisplayMode() const=0;
+    virtual const char* getDefaultDisplayMode() const;
     /// returns a list of all possible display modes
-    virtual std::vector<std::string> getDisplayModes(void) const=0;
+    virtual std::vector<std::string> getDisplayModes(void) const;
     /// Hides the view provider
     virtual void hide(void);
     /// Shows the view provider
@@ -313,7 +313,7 @@ public:
     //restoring the object from document: this may itnerest extensions, hence call them
     virtual void Restore(Base::XMLReader& reader);
 
-protected:
+
     /** @name Display mask modes
      * Mainly controls an SoSwitch node which selects the display mask modes.
      * The number of display mask modes doesn't necessarily match with the number
@@ -332,6 +332,8 @@ protected:
     std::vector<std::string> getDisplayMaskModes() const;
     void setDefaultMode(int);
     //@}
+    
+protected:
     /** Helper method to get picked entities while editing.
      * It's in the responsibility of the caller to delete the returned instance.
      */
diff --git a/src/Gui/ViewProviderDocumentObject.cpp b/src/Gui/ViewProviderDocumentObject.cpp
index 9dbd97f85..df1ac8971 100644
--- a/src/Gui/ViewProviderDocumentObject.cpp
+++ b/src/Gui/ViewProviderDocumentObject.cpp
@@ -42,6 +42,7 @@
 #include "MDIView.h"
 #include "TaskView/TaskAppearance.h"
 #include "ViewProviderDocumentObject.h"
+#include "ViewProviderExtension.h"
 #include <Gui/ViewProviderDocumentObjectPy.h>
 
 
@@ -160,7 +161,7 @@ void ViewProviderDocumentObject::attach(App::DocumentObject *pcObj)
 {
     // save Object pointer
     pcObject = pcObj;
-
+    
     // Retrieve the supported display modes of the view provider
     aDisplayModesArray = this->getDisplayModes();
 
@@ -179,6 +180,11 @@ void ViewProviderDocumentObject::attach(App::DocumentObject *pcObj)
     const char* defmode = this->getDefaultDisplayMode();
     if (defmode)
         DisplayMode.setValue(defmode);
+    
+    //attach the extensions
+    auto vector = getExtensionsDerivedFromType<Gui::ViewProviderExtension>();
+    for(Gui::ViewProviderExtension* ext : vector)
+        ext->extensionAttach(pcObj);
 }
 
 Gui::Document* ViewProviderDocumentObject::getDocument() const
@@ -265,18 +271,6 @@ void ViewProviderDocumentObject::setActiveMode()
         ViewProvider::hide();
 }
 
-const char* ViewProviderDocumentObject::getDefaultDisplayMode() const
-{
-    // We use the first item then
-    return 0;
-}
-
-std::vector<std::string> ViewProviderDocumentObject::getDisplayModes(void) const
-{
-    // empty
-    return std::vector<std::string>();
-}
-
 PyObject* ViewProviderDocumentObject::getPyObject()
 {
     if (!pyViewObject)
diff --git a/src/Gui/ViewProviderDocumentObject.h b/src/Gui/ViewProviderDocumentObject.h
index 358b247c4..ebe24ccf0 100644
--- a/src/Gui/ViewProviderDocumentObject.h
+++ b/src/Gui/ViewProviderDocumentObject.h
@@ -62,10 +62,6 @@ public:
     App::PropertyBool Visibility;
 
     virtual void attach(App::DocumentObject *pcObject);
-    /// Get the default display mode
-    virtual const char* getDefaultDisplayMode() const;
-    /// Return a list of all possible modes
-    virtual std::vector<std::string> getDisplayModes(void) const;
     /// Set the active mode, i.e. the first item of the 'Display' property.
     void setActiveMode();
     /// Hide the object in the view
@@ -78,8 +74,6 @@ public:
 
     /// Run a redraw
     void updateView();
-    /// Gets called if some of the property hade bin changed
-    virtual void updateData(const App::Property*){}
     /// Get the object of this ViewProvider object
     App::DocumentObject *getObject(void) const {return pcObject;}
     /// Get the GUI document to this ViewProvider object
diff --git a/src/Gui/ViewProviderExtension.cpp b/src/Gui/ViewProviderExtension.cpp
index dd9c746b7..4b6f67774 100644
--- a/src/Gui/ViewProviderExtension.cpp
+++ b/src/Gui/ViewProviderExtension.cpp
@@ -57,4 +57,7 @@ ViewProviderDocumentObject* ViewProviderExtension::getExtendedViewProvider() {
     return static_cast<ViewProviderDocumentObject*>(getExtendedContainer());
 }
 
+void ViewProviderExtension::extensionUpdateData(const App::Property*) {
+
+}
 
diff --git a/src/Gui/ViewProviderExtension.h b/src/Gui/ViewProviderExtension.h
index 335820fd9..ae8e0d75e 100644
--- a/src/Gui/ViewProviderExtension.h
+++ b/src/Gui/ViewProviderExtension.h
@@ -71,6 +71,16 @@ public:
     
     virtual void extensionRestore(Base::XMLReader& reader) { };
     
+    virtual SoSeparator* extensionGetFrontRoot(void) const {return nullptr;}
+    virtual SoGroup*     extensionGetChildRoot(void) const {return nullptr;}
+    virtual SoSeparator* extensionGetBackRoot(void) const {return nullptr;}
+    virtual void extensionAttach(App::DocumentObject* pcObject) { };
+    virtual void extensionSetDisplayMode(const char* ModeName) { };
+    virtual std::vector<std::string> extensionGetDisplayModes(void) const {return std::vector<std::string>();};
+
+    //update data of extended opject
+    virtual void extensionUpdateData(const App::Property*);
+    
 private:
     Gui::ViewProviderDocumentObject* m_viewBase = nullptr;
 };
diff --git a/src/Gui/ViewProviderGeoFeatureGroup.cpp b/src/Gui/ViewProviderGeoFeatureGroup.cpp
index 68d65b5df..4d4f0c6aa 100644
--- a/src/Gui/ViewProviderGeoFeatureGroup.cpp
+++ b/src/Gui/ViewProviderGeoFeatureGroup.cpp
@@ -36,58 +36,17 @@
 using namespace Gui;
 
 
-PROPERTY_SOURCE(Gui::ViewProviderGeoFeatureGroup, Gui::ViewProviderDocumentObjectGroup)
+PROPERTY_SOURCE_WITH_EXTENSIONS(Gui::ViewProviderGeoFeatureGroup, Gui::ViewProviderDocumentObject, (Gui::ViewProviderGeoFeatureGroupExtension))
 
 ViewProviderGeoFeatureGroup::ViewProviderGeoFeatureGroup()
 {
-    pcGroupChildren = new SoGroup();
-    pcGroupChildren->ref();
+    ViewProviderGeoFeatureGroupExtension::initExtension(this);
 }
 
 ViewProviderGeoFeatureGroup::~ViewProviderGeoFeatureGroup()
 {
-    pcGroupChildren->unref();
-    pcGroupChildren = 0;
 }
 
-std::vector<App::DocumentObject*> ViewProviderGeoFeatureGroup::claimChildren3D(void) const {
-    return dynamic_cast<App::GeoFeatureGroupExtension *>(getObject()->getExtension(App::GeoFeatureGroupExtension::getClassTypeId()))->getGeoSubObjects ();
-}
-
-void ViewProviderGeoFeatureGroup::attach(App::DocumentObject* pcObject)
-{
-    Gui::ViewProviderDocumentObjectGroup::attach(pcObject);
-    addDisplayMaskMode(pcGroupChildren, "Group");
-}
-
-void ViewProviderGeoFeatureGroup::setDisplayMode(const char* ModeName)
-{
-    if ( strcmp("Group",ModeName)==0 )
-        setDisplayMaskMode("Group");
-
-    ViewProviderDocumentObjectGroup::setDisplayMode( ModeName );
-}
-
-std::vector<std::string> ViewProviderGeoFeatureGroup::getDisplayModes(void) const
-{
-    // get the modes of the father
-    std::vector<std::string> StrList = ViewProviderDocumentObjectGroup::getDisplayModes();
-
-    // add your own modes
-    StrList.push_back("Group");
-
-    return StrList;
-}
-
-void ViewProviderGeoFeatureGroup::updateData(const App::Property* prop)
-{
-    App::GeoFeatureGroupExtension *obj = dynamic_cast<App::GeoFeatureGroupExtension*> ( getObject()->getExtension(App::GeoFeatureGroupExtension::getClassTypeId()) );
-    if (prop == &obj->Placement) {
-        setTransformation ( obj->Placement.getValue().toMatrix() );
-    } else {
-        ViewProviderDocumentObjectGroup::updateData ( prop );
-    }
-}
 
 // Python feature -----------------------------------------------------------------------
 
diff --git a/src/Gui/ViewProviderGeoFeatureGroup.h b/src/Gui/ViewProviderGeoFeatureGroup.h
index 33a5e2c6a..354f0ee95 100644
--- a/src/Gui/ViewProviderGeoFeatureGroup.h
+++ b/src/Gui/ViewProviderGeoFeatureGroup.h
@@ -26,40 +26,22 @@
 #define GUI_VIEWPROVIDER_ViewProviderGeoFeatureGroup_H
 
 
-#include "ViewProviderDocumentObjectGroup.h"
+#include "ViewProviderDocumentObject.h"
+#include "ViewProviderGeoFeatureGroupExtension.h"
+#include "ViewProviderPythonFeature.h"
 
 namespace Gui {
 
-class GuiExport ViewProviderGeoFeatureGroup : public ViewProviderDocumentObjectGroup
+class GuiExport ViewProviderGeoFeatureGroup : public ViewProviderDocumentObject,
+                                              public ViewProviderGeoFeatureGroupExtension
 {
-    PROPERTY_HEADER(Gui::ViewProviderGeoFeatureGroup);
+    PROPERTY_HEADER_WITH_EXTENSIONS(Gui::ViewProviderGeoFeatureGroup);
 
 public:
     /// constructor.
     ViewProviderGeoFeatureGroup();
     /// destructor.
     virtual ~ViewProviderGeoFeatureGroup();
-
-    virtual std::vector<App::DocumentObject*> claimChildren3D(void)const;
-
-    virtual SoGroup* getChildRoot(void) const {return pcGroupChildren;};
-
-    virtual void attach(App::DocumentObject* pcObject);
-    virtual void setDisplayMode(const char* ModeName);
-    virtual std::vector<std::string> getDisplayModes(void) const;
-
-    /// Show the object in the view: suppresses behavior of DocumentObjectGroup
-    virtual void show(void) {
-        ViewProviderDocumentObject::show();
-    }
-    /// Hide the object in the view: suppresses behavior of DocumentObjectGroup
-    virtual void hide(void) {
-        ViewProviderDocumentObject::hide();
-    }
-
-    virtual void updateData(const App::Property*);
-protected:
-    SoGroup *pcGroupChildren;
 };
 
 typedef ViewProviderPythonFeatureT<ViewProviderGeoFeatureGroup> ViewProviderGeoFeatureGroupPython;
diff --git a/src/Gui/ViewProviderGeoFeatureGroupExtension.cpp b/src/Gui/ViewProviderGeoFeatureGroupExtension.cpp
new file mode 100644
index 000000000..465b0b362
--- /dev/null
+++ b/src/Gui/ViewProviderGeoFeatureGroupExtension.cpp
@@ -0,0 +1,90 @@
+/***************************************************************************
+ *   Copyright (c) 2016 Stefan Tröger <stefantroeger@gmx.net>              *
+ *                                                                         *
+ *   This file is part of the FreeCAD CAx development system.              *
+ *                                                                         *
+ *   This library is free software; you can redistribute it and/or         *
+ *   modify it under the terms of the GNU Library General Public           *
+ *   License as published by the Free Software Foundation; either          *
+ *   version 2 of the License, or (at your option) any later version.      *
+ *                                                                         *
+ *   This library  is distributed in the hope that it will be useful,      *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU Library General Public License for more details.                  *
+ *                                                                         *
+ *   You should have received a copy of the GNU Library General Public     *
+ *   License along with this library; see the file COPYING.LIB. If not,    *
+ *   write to the Free Software Foundation, Inc., 59 Temple Place,         *
+ *   Suite 330, Boston, MA  02111-1307, USA                                *
+ *                                                                         *
+ ***************************************************************************/
+
+
+#include "PreCompiled.h"
+
+#ifndef _PreComp_
+#endif
+
+#include "ViewProviderGeoFeatureGroupExtension.h"
+#include <App/GeoFeatureGroupExtension.h>
+#include <Inventor/nodes/SoGroup.h>
+
+using namespace Gui;
+
+PROPERTY_SOURCE(Gui::ViewProviderGeoFeatureGroupExtension, Gui::ViewProviderGroupExtension)
+
+ViewProviderGeoFeatureGroupExtension::ViewProviderGeoFeatureGroupExtension()
+{
+    initExtension(ViewProviderGeoFeatureGroupExtension::getClassTypeId());
+    
+    pcGroupChildren = new SoGroup();
+    pcGroupChildren->ref();
+}
+
+ViewProviderGeoFeatureGroupExtension::~ViewProviderGeoFeatureGroupExtension()
+{
+    pcGroupChildren->unref();
+    pcGroupChildren = 0;
+}
+
+
+std::vector<App::DocumentObject*> ViewProviderGeoFeatureGroupExtension::extensionClaimChildren3D(void) const {
+    auto* ext = getExtendedViewProvider()->getObject()->getExtensionByType<App::GeoFeatureGroupExtension>();
+    return ext->getGeoSubObjects();
+}
+
+void ViewProviderGeoFeatureGroupExtension::extensionAttach(App::DocumentObject* pcObject)
+{
+    ViewProviderGroupExtension::extensionAttach(pcObject);
+    getExtendedViewProvider()->addDisplayMaskMode(pcGroupChildren, "Group");
+}
+
+void ViewProviderGeoFeatureGroupExtension::extensionSetDisplayMode(const char* ModeName)
+{
+    if ( strcmp("Group",ModeName)==0 )
+        getExtendedViewProvider()->setDisplayMaskMode("Group");
+
+    ViewProviderGroupExtension::extensionSetDisplayMode( ModeName );
+}
+
+std::vector<std::string> ViewProviderGeoFeatureGroupExtension::extensionGetDisplayModes(void) const
+{
+    // get the modes of the father
+    std::vector<std::string> StrList = ViewProviderGroupExtension::extensionGetDisplayModes();
+
+    // add your own modes
+    StrList.push_back("Group");
+
+    return StrList;
+}
+
+void ViewProviderGeoFeatureGroupExtension::extensionUpdateData(const App::Property* prop)
+{
+    auto obj = getExtendedViewProvider()->getObject()->getExtensionByType<App::GeoFeatureGroupExtension>();
+    if (prop == &obj->Placement) {
+        getExtendedViewProvider()->setTransformation ( obj->Placement.getValue().toMatrix() );
+    } else {
+        ViewProviderGroupExtension::extensionUpdateData ( prop );
+    }
+}
\ No newline at end of file
diff --git a/src/Gui/ViewProviderGeoFeatureGroupExtension.h b/src/Gui/ViewProviderGeoFeatureGroupExtension.h
new file mode 100644
index 000000000..575a4e399
--- /dev/null
+++ b/src/Gui/ViewProviderGeoFeatureGroupExtension.h
@@ -0,0 +1,67 @@
+/***************************************************************************
+ *   Copyright (c) 2011 Juergen Riegel <FreeCAD@juergen-riegel.net>        *
+ *   Copyright (c) 2015 Alexander Golubev (Fat-Zer) <fatzer2@gmail.com>    *
+ *   Copyright (c) 2016 Stefan Tröger <stefantroeger@gmx.net>              *
+ *                                                                         *
+ *   This file is part of the FreeCAD CAx development system.              *
+ *                                                                         *
+ *   This library is free software; you can redistribute it and/or         *
+ *   modify it under the terms of the GNU Library General Public           *
+ *   License as published by the Free Software Foundation; either          *
+ *   version 2 of the License, or (at your option) any later version.      *
+ *                                                                         *
+ *   This library  is distributed in the hope that it will be useful,      *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU Library General Public License for more details.                  *
+ *                                                                         *
+ *   You should have received a copy of the GNU Library General Public     *
+ *   License along with this library; see the file COPYING.LIB. If not,    *
+ *   write to the Free Software Foundation, Inc., 59 Temple Place,         *
+ *   Suite 330, Boston, MA  02111-1307, USA                                *
+ *                                                                         *
+ ***************************************************************************/
+
+
+#ifndef GUI_VIEWPROVIDERGEOFEATUREGROUPEXTENSION_H
+#define GUI_VIEWPROVIDERGEOFEATUREGROUPEXTENSION_H
+
+#include <App/Extension.h>
+#include "ViewProviderGroupExtension.h"
+
+namespace Gui
+{
+
+class GuiExport ViewProviderGeoFeatureGroupExtension : public ViewProviderGroupExtension
+{
+    PROPERTY_HEADER(Gui::ViewProviderGeoFeatureGroupExtension);
+
+public:
+    /// Constructor
+    ViewProviderGeoFeatureGroupExtension(void);
+    virtual ~ViewProviderGeoFeatureGroupExtension();
+
+    virtual std::vector<App::DocumentObject*> extensionClaimChildren3D(void)const override;
+    virtual SoGroup* extensionGetChildRoot(void) const override {return pcGroupChildren;};
+    virtual void extensionAttach(App::DocumentObject* pcObject) override;
+    virtual void extensionSetDisplayMode(const char* ModeName) override;
+    virtual std::vector<std::string> extensionGetDisplayModes(void) const override;
+
+    /// Show the object in the view: suppresses behavior of DocumentObjectGroup
+    virtual void extensionShow(void) override {
+        ViewProviderExtension::extensionShow();
+    }
+    /// Hide the object in the view: suppresses behavior of DocumentObjectGroup
+    virtual void extensionHide(void) override {
+        ViewProviderExtension::extensionHide();
+    }
+
+    virtual void extensionUpdateData(const App::Property*) override;
+    
+protected:
+    SoGroup *pcGroupChildren;
+};
+
+} //namespace Gui
+
+#endif // GUI_VIEWPROVIDERGEOFEATUREGROUPEXTENSION_H
diff --git a/src/Gui/ViewProviderGroupExtension.cpp b/src/Gui/ViewProviderGroupExtension.cpp
index d77af3076..085ac3874 100644
--- a/src/Gui/ViewProviderGroupExtension.cpp
+++ b/src/Gui/ViewProviderGroupExtension.cpp
@@ -76,9 +76,7 @@ bool ViewProviderGroupExtension::extensionCanDropObjects() const {
 
 bool ViewProviderGroupExtension::extensionCanDropObject(App::DocumentObject* obj) const {
     
-    auto vector = getExtendedViewProvider()->getObject()->getExtensionsDerivedFromType<App::GroupExtension>();
-    assert(vector.size() == 1);
-    App::GroupExtension* group = vector.front();
+    auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::GroupExtension>();
     
     //we cannot drop thing of this group into it again
     if (group->hasObject(obj))
@@ -132,10 +130,9 @@ void ViewProviderGroupExtension::extensionDropObject(App::DocumentObject* obj) {
 
 std::vector< App::DocumentObject* > ViewProviderGroupExtension::extensionClaimChildren(void) const {
     
-    auto ext = getExtendedViewProvider()->getObject()->getExtensionsDerivedFromType<App::GroupExtension>();
-    assert(ext.size() == 1);
+    auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::GroupExtension>();
     
-    return std::vector<App::DocumentObject*>(ext.front()->Group.getValues());
+    return std::vector<App::DocumentObject*>(group->Group.getValues());
 }
 
 
@@ -144,10 +141,8 @@ void ViewProviderGroupExtension::extensionShow(void) {
     // when reading the Visibility property from file then do not hide the
     // objects of this group because they have stored their visibility status, too
     if (!getExtendedViewProvider()->Visibility.testStatus(App::Property::User1) && !this->visible) {
-        auto ext = getExtendedViewProvider()->getObject()->getExtensionsDerivedFromType<App::GroupExtension>();
-        assert(ext.size() == 1);
-    
-        App::GroupExtension* group = ext.front();
+        auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::GroupExtension>();
+        
         const std::vector<App::DocumentObject*> & links = group->Group.getValues();
         Gui::Document* doc = Application::Instance->getDocument(group->getExtendedObject()->getDocument());
         for (std::vector<App::DocumentObject*>::const_iterator it = links.begin(); it != links.end(); ++it) {
@@ -167,10 +162,8 @@ void ViewProviderGroupExtension::extensionHide(void) {
     // objects of this group because they have stored their visibility status, too
     if (!getExtendedViewProvider()->Visibility.testStatus(App::Property::User1) && this->visible) {
         
-        auto ext = getExtendedViewProvider()->getObject()->getExtensionsDerivedFromType<App::GroupExtension>();
-        assert(ext.size() == 1);
-    
-        App::GroupExtension* group = ext.front();
+        auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::GroupExtension>();
+        
         const std::vector<App::DocumentObject*> & links = group->Group.getValues();
         Gui::Document* doc = Application::Instance->getDocument(getExtendedViewProvider()->getObject()->getDocument());
         for (std::vector<App::DocumentObject*>::const_iterator it = links.begin(); it != links.end(); ++it) {
@@ -186,10 +179,7 @@ void ViewProviderGroupExtension::extensionHide(void) {
 
 bool ViewProviderGroupExtension::extensionOnDelete(const std::vector< std::string >& vec) {
     
-    auto ext = getExtendedViewProvider()->getObject()->getExtensionsDerivedFromType<App::GroupExtension>();
-    assert(ext.size() == 1);
-    
-    App::GroupExtension *group = ext.front();
+    auto* group = getExtendedViewProvider()->getObject()->getExtensionByType<App::GroupExtension>();
     // If the group is nonempty ask the user if he wants to delete it's content
     if ( group->Group.getSize () ) {
         QMessageBox::StandardButton choice =