diff --git a/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.cpp b/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.cpp
index f6394ea144..26102b6d3e 100644
--- a/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.cpp
+++ b/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.cpp
@@ -1,201 +1,244 @@
 /*===================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical and Biological Informatics.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 
 #include "QmitkMultiNodeSelectionWidget.h"
 
 #include <algorithm>
 
 #include "QmitkNodeSelectionDialog.h"
 #include "QmitkCustomVariants.h"
 #include "internal/QmitkNodeSelectionListItemWidget.h"
 
 QmitkMultiNodeSelectionWidget::QmitkMultiNodeSelectionWidget(QWidget* parent) : QmitkAbstractNodeSelectionWidget(parent)
 {
   m_Controls.setupUi(this);
+  m_Overlay = new QmitkSimpleTextOverlayWidget(m_Controls.list);
+  m_Overlay->setVisible(false);
+  m_CheckFunction = [](const NodeList &) { return ""; };
 
   this->UpdateList();
   this->UpdateInfo();
 
   connect(m_Controls.btnChange, SIGNAL(clicked(bool)), this, SLOT(OnEditSelection()));
 }
 
 QmitkMultiNodeSelectionWidget::NodeList QmitkMultiNodeSelectionWidget::CompileEmitSelection() const
 {
   NodeList result;
 
   for (int i = 0; i < m_Controls.list->count(); ++i)
   {
     QListWidgetItem* item = m_Controls.list->item(i);
 
     auto node = item->data(Qt::UserRole).value<mitk::DataNode::Pointer>();
     result.append(node);
   }
 
 
   if (!m_SelectOnlyVisibleNodes)
   {
     for (auto node : m_CurrentSelection)
     {
       if (!result.contains(node))
       {
         result.append(node);
       }
     }
   }
 
   return result;
 }
 
 void QmitkMultiNodeSelectionWidget::OnNodePredicateChanged(mitk::NodePredicateBase* /*newPredicate*/)
 {
   this->UpdateInfo();
   this->UpdateList();
 };
 
 void QmitkMultiNodeSelectionWidget::OnDataStorageChanged()
 {
   this->UpdateInfo();
   this->UpdateList();
 };
 
 QmitkMultiNodeSelectionWidget::NodeList QmitkMultiNodeSelectionWidget::GetSelectedNodes() const
 {
   return m_CurrentSelection;
 };
 
+void QmitkMultiNodeSelectionWidget::SetSelectionCheckFunction(const SelectionCheckFunctionType &checkFunction)
+{
+  m_CheckFunction = checkFunction;
+
+  auto newEmission = this->CompileEmitSelection();
+  auto newCheckResponse = m_CheckFunction(newEmission);
+
+  if (newCheckResponse.empty() && !m_CheckResponse.empty())
+  {
+    emit CurrentSelectionChanged(newEmission);
+  }
+  m_CheckResponse = newCheckResponse;
+  this->UpdateInfo();
+};
+
 void QmitkMultiNodeSelectionWidget::OnEditSelection()
 {
   QmitkNodeSelectionDialog* dialog = new QmitkNodeSelectionDialog(this, m_PopUpTitel, m_PopUpHint);
 
   dialog->SetDataStorage(m_DataStorage.Lock());
   dialog->SetNodePredicate(m_NodePredicate);
   dialog->SetCurrentSelection(this->CompileEmitSelection());
   dialog->SetSelectOnlyVisibleNodes(m_SelectOnlyVisibleNodes);
   dialog->SetSelectionMode(QAbstractItemView::MultiSelection);
 
   m_Controls.btnChange->setChecked(true);
   if (dialog->exec())
   {
     auto lastEmission = this->CompileEmitSelection();
 
     m_CurrentSelection = dialog->GetSelectedNodes();
     this->UpdateList();
-    this->UpdateInfo();
 
     auto newEmission = this->CompileEmitSelection();
 
+    m_CheckResponse = m_CheckFunction(newEmission);
+    this->UpdateInfo();
+
     if (!EqualNodeSelections(lastEmission, newEmission))
     {
-      emit CurrentSelectionChanged(newEmission);
+      if (m_CheckResponse.empty())
+      {
+        emit CurrentSelectionChanged(newEmission);
+      }
     }
   }
   m_Controls.btnChange->setChecked(false);
 
   delete dialog;
 };
 
 void QmitkMultiNodeSelectionWidget::UpdateInfo()
 {
-  m_Controls.infoLabel->setVisible(m_Controls.list->count()==0);
-
   if (!m_Controls.list->count())
   {
     if (m_IsOptional)
     {
-      m_Controls.infoLabel->setText(m_EmptyInfo);
+      m_Overlay->SetOverlayText(m_EmptyInfo);
     }
     else
     {
-      m_Controls.infoLabel->setText(m_InvalidInfo);
+      m_Overlay->SetOverlayText(m_InvalidInfo);
+    }
+  }
+  else
+  {
+    if (!m_CheckResponse.empty())
+    {
+      m_Overlay->SetOverlayText(QString::fromStdString(m_CheckResponse));
     }
   }
 
+  m_Overlay->setVisible(m_Controls.list->count() == 0 || !m_CheckResponse.empty());
+
   for (auto i = 0; i < m_Controls.list->count(); ++i)
   {
     auto item = m_Controls.list->item(i);
     auto widget = qobject_cast<QmitkNodeSelectionListItemWidget*>(m_Controls.list->itemWidget(item));
     widget->SetClearAllowed(m_IsOptional || m_CurrentSelection.size() > 1);
   }
 };
 
 void QmitkMultiNodeSelectionWidget::UpdateList()
 {
   m_Controls.list->clear();
 
   for (auto node : m_CurrentSelection)
   {
     if (m_NodePredicate.IsNull() || m_NodePredicate->CheckNode(node))
     {
       QListWidgetItem *newItem = new QListWidgetItem;
 
       newItem->setSizeHint(QSize(0, 40));
       QmitkNodeSelectionListItemWidget* widget = new QmitkNodeSelectionListItemWidget;
 
       widget->SetSelectedNode(node);
       widget->SetClearAllowed(m_IsOptional || m_CurrentSelection.size() > 1);
 
       connect(widget, SIGNAL(ClearSelection(mitk::DataNode*)), this, SLOT(OnClearSelection(mitk::DataNode*)));
       newItem->setData(Qt::UserRole, QVariant::fromValue<mitk::DataNode::Pointer>(node));
 
       m_Controls.list->addItem(newItem);
       m_Controls.list->setItemWidget(newItem, widget);
     }
   }
 };
 
 void QmitkMultiNodeSelectionWidget::SetSelectOnlyVisibleNodes(bool selectOnlyVisibleNodes)
 {
   auto lastEmission = this->CompileEmitSelection();
 
   m_SelectOnlyVisibleNodes = selectOnlyVisibleNodes;
 
   auto newEmission = this->CompileEmitSelection();
 
   if (!EqualNodeSelections(lastEmission, newEmission))
   {
-    emit CurrentSelectionChanged(newEmission);
+    m_CheckResponse = m_CheckFunction(newEmission);
+    if (m_CheckResponse.empty())
+    {
+      emit CurrentSelectionChanged(newEmission);
+    }
     this->UpdateList();
     this->UpdateInfo();
   }
 };
 
 void QmitkMultiNodeSelectionWidget::SetCurrentSelection(NodeList selectedNodes)
 {
   auto lastEmission = this->CompileEmitSelection();
 
   m_CurrentSelection = selectedNodes;
   this->UpdateList();
 
   auto newEmission = this->CompileEmitSelection();
 
   if (!EqualNodeSelections(lastEmission, newEmission))
   {
-    emit CurrentSelectionChanged(newEmission);
+    m_CheckResponse = m_CheckFunction(newEmission);
+    if (m_CheckResponse.empty())
+    {
+      emit CurrentSelectionChanged(newEmission);
+    }
     this->UpdateInfo();
   }
 };
 
 void QmitkMultiNodeSelectionWidget::OnClearSelection(mitk::DataNode* node)
 {
   auto finding = std::find(std::begin(m_CurrentSelection), std::end(m_CurrentSelection), node);
   m_CurrentSelection.erase(finding);
 
   this->UpdateList();
-  this->UpdateInfo();
   auto newEmission = this->CompileEmitSelection();
-  emit CurrentSelectionChanged(newEmission);
+  m_CheckResponse = m_CheckFunction(newEmission);
+
+  if (m_CheckResponse.empty())
+  {
+    emit CurrentSelectionChanged(newEmission);
+  }
+  this->UpdateInfo();
 };
diff --git a/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.h b/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.h
index 8c1f5ce3b1..28cc17ed33 100644
--- a/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.h
+++ b/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.h
@@ -1,70 +1,88 @@
 /*===================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical and Biological Informatics.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 
 #ifndef QMITK_MULTI_NODE_SELECTION_WIDGET_H
 #define QMITK_MULTI_NODE_SELECTION_WIDGET_H
 
 #include <mitkDataStorage.h>
 #include <mitkWeakPointer.h>
 #include <mitkNodePredicateBase.h>
 
+#include "QmitkSimpleTextOverlayWidget.h"
+
 #include "org_mitk_gui_qt_common_Export.h"
 
 #include "ui_QmitkMultiNodeSelectionWidget.h"
 
 #include <QmitkAbstractNodeSelectionWidget.h>
 
 class QmitkAbstractDataStorageModel;
 class QAbstractItemVew;
 
 /**
 * \class QmitkMultiNodeSelectionWidget
-* \brief Widget that allows to show and edit the content of an mitk::IsoDoseLevel instance.
+* \brief Widget that allows to perform and represents a multiple node selection.
 */
 class MITK_QT_COMMON QmitkMultiNodeSelectionWidget : public QmitkAbstractNodeSelectionWidget
 {
   Q_OBJECT
 
 public:
   explicit QmitkMultiNodeSelectionWidget(QWidget* parent = nullptr);
 
   using NodeList = QmitkAbstractNodeSelectionWidget::NodeList;
 
   NodeList GetSelectedNodes() const;
 
+  /**Helper function that is used to check the given selection for consistency.
+   Returning an empty string assumes that everything is alright and the selection
+   is valid. If the string is not empty, the content of the string will be used
+   as error message in the overlay to indicate the problem.*/
+  using SelectionCheckFunctionType = std::function<std::string(const NodeList &)>;
+  /**A selection check function can be set. If set the widget uses this function to
+   check the made/set selection. If the selection is valid, everything is fine.
+   If selection is indicated as invalid, it will not be communicated by the widget
+   (no signal emission.*/
+  void SetSelectionCheckFunction(const SelectionCheckFunctionType &checkFunction);
+
 public Q_SLOTS:
   virtual void SetSelectOnlyVisibleNodes(bool selectOnlyVisibleNodes) override;
   virtual void SetCurrentSelection(NodeList selectedNodes) override;
   void OnEditSelection();
 
 protected Q_SLOTS:
   void OnClearSelection(mitk::DataNode* node);
 
 protected:
   NodeList CompileEmitSelection() const;
 
   virtual void UpdateInfo() override;
   virtual void UpdateList();
 
   virtual void OnNodePredicateChanged(mitk::NodePredicateBase* newPredicate) override;
   virtual void OnDataStorageChanged() override;
 
   NodeList m_CurrentSelection;
 
+  QmitkSimpleTextOverlayWidget* m_Overlay;
+
+  SelectionCheckFunctionType m_CheckFunction;
+  std::string m_CheckResponse;
+
   Ui_QmitkMultiNodeSelectionWidget m_Controls;
 };
 #endif // QmitkMultiNodeSelectionWidget_H
diff --git a/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.ui b/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.ui
index 87eae80c7e..adc62f5f11 100644
--- a/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.ui
+++ b/Plugins/org.mitk.gui.qt.common/src/QmitkMultiNodeSelectionWidget.ui
@@ -1,92 +1,82 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <ui version="4.0">
  <class>QmitkMultiNodeSelectionWidget</class>
  <widget class="QWidget" name="QmitkMultiNodeSelectionWidget">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>391</width>
     <height>265</height>
    </rect>
   </property>
   <property name="windowTitle">
    <string>Form</string>
   </property>
   <layout class="QVBoxLayout" name="verticalLayout">
    <property name="spacing">
     <number>0</number>
    </property>
    <property name="leftMargin">
     <number>0</number>
    </property>
    <property name="topMargin">
     <number>0</number>
    </property>
    <property name="rightMargin">
     <number>0</number>
    </property>
    <property name="bottomMargin">
     <number>0</number>
    </property>
    <item>
     <widget class="QListWidget" name="list">
      <property name="editTriggers">
       <set>QAbstractItemView::NoEditTriggers</set>
      </property>
      <property name="dragEnabled">
       <bool>false</bool>
      </property>
      <property name="dragDropMode">
       <enum>QAbstractItemView::NoDragDrop</enum>
      </property>
      <property name="defaultDropAction">
       <enum>Qt::MoveAction</enum>
      </property>
      <item>
       <property name="text">
        <string>1</string>
       </property>
      </item>
      <item>
       <property name="text">
        <string>2</string>
       </property>
      </item>
      <item>
       <property name="text">
        <string>3</string>
       </property>
      </item>
      <item>
       <property name="text">
        <string>4</string>
       </property>
      </item>
     </widget>
    </item>
-   <item>
-    <widget class="QLabel" name="infoLabel">
-     <property name="text">
-      <string>TextLabel</string>
-     </property>
-     <property name="wordWrap">
-      <bool>true</bool>
-     </property>
-    </widget>
-   </item>
    <item>
     <widget class="QPushButton" name="btnChange">
      <property name="text">
       <string>Change selection</string>
      </property>
      <property name="checkable">
       <bool>true</bool>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <resources/>
  <connections/>
 </ui>
diff --git a/Plugins/org.mitk.gui.qt.common/src/QmitkSingleNodeSelectionWidget.h b/Plugins/org.mitk.gui.qt.common/src/QmitkSingleNodeSelectionWidget.h
index 9cdccde270..4f67d11568 100644
--- a/Plugins/org.mitk.gui.qt.common/src/QmitkSingleNodeSelectionWidget.h
+++ b/Plugins/org.mitk.gui.qt.common/src/QmitkSingleNodeSelectionWidget.h
@@ -1,76 +1,76 @@
 /*===================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical and Biological Informatics.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 
 #ifndef QMITK_SINGLE_NODE_SELECTION_WIDGET_H
 #define QMITK_SINGLE_NODE_SELECTION_WIDGET_H
 
 #include <mitkDataStorage.h>
 #include <mitkWeakPointer.h>
 #include <mitkNodePredicateBase.h>
 
 #include "org_mitk_gui_qt_common_Export.h"
 
 #include "ui_QmitkSingleNodeSelectionWidget.h"
 
 #include <QmitkAbstractNodeSelectionWidget.h>
 #include <QmitkNodeSelectionButton.h>
 
 class QmitkAbstractDataStorageModel;
 
 /**
 * \class QmitkSingleNodeSelectionWidget
-* \brief Widget that that represents a node selection. It acts like a button. Clicking on it
+* \brief Widget that represents a node selection. It acts like a button. Clicking on it
 * allows to change the selection.
 */
 class MITK_QT_COMMON QmitkSingleNodeSelectionWidget : public QmitkAbstractNodeSelectionWidget
 {
   Q_OBJECT
 
 public:
   explicit QmitkSingleNodeSelectionWidget(QWidget* parent = nullptr);
   ~QmitkSingleNodeSelectionWidget();
 
   mitk::DataNode::Pointer GetSelectedNode() const;
 
   using NodeList = QmitkAbstractNodeSelectionWidget::NodeList;
 
 public Q_SLOTS:
   virtual void SetSelectOnlyVisibleNodes(bool selectOnlyVisibleNodes) override;
   virtual void SetCurrentSelection(NodeList selectedNodes) override;
 
 protected Q_SLOTS:
   virtual void OnClearSelection();
 
 protected:
   mitk::DataNode::Pointer ExtractCurrentValidSelection(const NodeList& nodes) const;
   NodeList CompileEmitSelection() const;
 
   virtual bool eventFilter(QObject *obj, QEvent *ev) override;
   void EditSelection();
   virtual void UpdateInfo() override;
 
   virtual void OnNodePredicateChanged(mitk::NodePredicateBase* newPredicate) override;
   virtual void OnDataStorageChanged() override;
 
 
   NodeList m_ExternalSelection;
   mitk::DataNode::Pointer m_SelectedNode;
 
   Ui_QmitkSingleNodeSelectionWidget m_Controls;
 };
 
 #endif // QmitkSingleNodeSelectionWidget_H
diff --git a/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestControls.ui b/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestControls.ui
index 66866a9712..77f8edc873 100644
--- a/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestControls.ui
+++ b/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestControls.ui
@@ -1,158 +1,173 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <ui version="4.0">
  <class>QmitkDataStorageViewerTestControls</class>
  <widget class="QWidget" name="QmitkDataStorageViewerTestControls">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>945</width>
-    <height>728</height>
+    <height>456</height>
    </rect>
   </property>
   <property name="minimumSize">
    <size>
     <width>0</width>
     <height>0</height>
    </size>
   </property>
   <property name="windowTitle">
    <string>Data storage viewer test</string>
   </property>
   <layout class="QGridLayout" name="gridLayout">
-   <item row="0" column="0">
-    <widget class="QListView" name="selectionListView"/>
-   </item>
-   <item row="0" column="1">
-    <widget class="QListView" name="selectionListView2"/>
-   </item>
    <item row="1" column="0">
     <widget class="QCheckBox" name="selectionProviderCheckBox">
      <property name="text">
       <string>Set as selection provider</string>
      </property>
     </widget>
    </item>
+   <item row="0" column="1">
+    <widget class="QListView" name="selectionListView2"/>
+   </item>
    <item row="1" column="1">
     <widget class="QCheckBox" name="selectionProviderCheckBox2">
      <property name="text">
       <string>Set as selection provider</string>
      </property>
     </widget>
    </item>
-   <item row="2" column="0">
-    <widget class="QCheckBox" name="selectionListenerCheckBox">
+   <item row="0" column="0">
+    <widget class="QListView" name="selectionListView"/>
+   </item>
+   <item row="7" column="0">
+    <widget class="QCheckBox" name="checkOnlyImages">
      <property name="text">
-      <string>Set as selection listener</string>
+      <string>Allow only images </string>
      </property>
     </widget>
    </item>
-   <item row="2" column="1">
-    <widget class="QCheckBox" name="selectionListenerCheckBox2">
+   <item row="9" column="0">
+    <widget class="QCheckBox" name="checkOptional">
      <property name="text">
-      <string>Set as selection listener</string>
+      <string>Is Optional</string>
      </property>
     </widget>
    </item>
-   <item row="3" column="0">
-    <widget class="QmitkSingleNodeSelectionWidget" name="singleSlot" native="true">
-     <property name="minimumSize">
-      <size>
-       <width>0</width>
-       <height>40</height>
-      </size>
+   <item row="4" column="1">
+    <widget class="QCheckBox" name="selectionProviderCheckBox4">
+     <property name="text">
+      <string>Set as selection provider</string>
      </property>
     </widget>
    </item>
-   <item row="3" column="1">
-    <widget class="QmitkMultiNodeSelectionWidget" name="multiSlot" native="true"/>
-   </item>
-   <item row="4" column="0">
-    <widget class="QCheckBox" name="selectionProviderCheckBox3">
+   <item row="6" column="1">
+    <widget class="QCheckBox" name="checkOnlyVisible_2">
      <property name="text">
-      <string>Set as selection provider</string>
+      <string>Only valid nodes</string>
      </property>
     </widget>
    </item>
-   <item row="5" column="0">
-    <widget class="QCheckBox" name="selectionListenerCheckBox3">
+   <item row="7" column="1">
+    <widget class="QCheckBox" name="checkOnlyImages_2">
      <property name="text">
-      <string>Set as selection listner</string>
+      <string>Allow only images
+(using NodePredicate feature and general invalid message)</string>
      </property>
     </widget>
    </item>
-   <item row="6" column="0">
-    <widget class="QCheckBox" name="checkOnlyVisible">
+   <item row="2" column="0">
+    <widget class="QCheckBox" name="selectionListenerCheckBox">
      <property name="text">
-      <string>Only valid nodes</string>
+      <string>Set as selection listener</string>
      </property>
     </widget>
    </item>
-   <item row="7" column="0">
-    <widget class="QCheckBox" name="checkOnlyImages">
+   <item row="2" column="1">
+    <widget class="QCheckBox" name="selectionListenerCheckBox2">
      <property name="text">
-      <string>Allow only images </string>
+      <string>Set as selection listener</string>
      </property>
     </widget>
    </item>
-   <item row="8" column="0">
-    <widget class="QCheckBox" name="checkOptional">
+   <item row="6" column="0">
+    <widget class="QCheckBox" name="checkOnlyVisible">
      <property name="text">
-      <string>Is Optional</string>
+      <string>Only valid nodes</string>
      </property>
     </widget>
    </item>
-   <item row="4" column="1">
-    <widget class="QCheckBox" name="selectionProviderCheckBox4">
+   <item row="5" column="0">
+    <widget class="QCheckBox" name="selectionListenerCheckBox3">
      <property name="text">
-      <string>Set as selection provider</string>
+      <string>Set as selection listner</string>
      </property>
     </widget>
    </item>
    <item row="5" column="1">
     <widget class="QCheckBox" name="selectionListenerCheckBox4">
      <property name="text">
       <string>Set as selection listner</string>
      </property>
     </widget>
    </item>
-   <item row="6" column="1">
-    <widget class="QCheckBox" name="checkOnlyVisible_2">
+   <item row="4" column="0">
+    <widget class="QCheckBox" name="selectionProviderCheckBox3">
      <property name="text">
-      <string>Only valid nodes</string>
+      <string>Set as selection provider</string>
      </property>
     </widget>
    </item>
-   <item row="7" column="1">
-    <widget class="QCheckBox" name="checkOnlyImages_2">
+   <item row="9" column="1">
+    <widget class="QCheckBox" name="checkOptional_2">
      <property name="text">
-      <string>Allow only images </string>
+      <string>Is Optional</string>
+     </property>
+    </widget>
+   </item>
+   <item row="3" column="0">
+    <widget class="QmitkSingleNodeSelectionWidget" name="singleSlot" native="true">
+     <property name="sizePolicy">
+      <sizepolicy hsizetype="Preferred" vsizetype="Minimum">
+       <horstretch>0</horstretch>
+       <verstretch>0</verstretch>
+      </sizepolicy>
+     </property>
+     <property name="minimumSize">
+      <size>
+       <width>0</width>
+       <height>40</height>
+      </size>
      </property>
     </widget>
    </item>
+   <item row="3" column="1">
+    <widget class="QmitkMultiNodeSelectionWidget" name="multiSlot" native="true"/>
+   </item>
    <item row="8" column="1">
-    <widget class="QCheckBox" name="checkOptional_2">
+    <widget class="QCheckBox" name="checkOnlyUneven">
      <property name="text">
-      <string>Is Optional</string>
+      <string>Allow only uneven selection count
+(using check funcktion feature)</string>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <customwidgets>
   <customwidget>
    <class>QmitkSingleNodeSelectionWidget</class>
    <extends>QWidget</extends>
    <header location="global">QmitkSingleNodeSelectionWidget.h</header>
    <container>1</container>
   </customwidget>
   <customwidget>
    <class>QmitkMultiNodeSelectionWidget</class>
    <extends>QWidget</extends>
    <header location="global">QmitkMultiNodeSelectionWidget.h</header>
    <container>1</container>
   </customwidget>
  </customwidgets>
  <resources/>
  <connections/>
 </ui>
diff --git a/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestView.cpp b/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestView.cpp
index 490fe3aa0d..99c850e6c0 100644
--- a/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestView.cpp
+++ b/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestView.cpp
@@ -1,247 +1,278 @@
 /*===================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical Image Computing.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 // data storage viewer test plugin
 #include "QmitkDataStorageViewerTestView.h"
 
 #include "mitkNodePredicateDataType.h"
 
 // berry
 #include <berryIWorkbenchWindow.h>
 
 // qt
 #include <QHBoxLayout>
 
 const std::string QmitkDataStorageViewerTestView::VIEW_ID = "org.mitk.views.datastorageviewertest";
 
 void QmitkDataStorageViewerTestView::SetFocus()
 {
   // nothing here
 }
 
 void QmitkDataStorageViewerTestView::CreateQtPartControl(QWidget* parent)
 {
   // create GUI widgets
   m_Controls.setupUi(parent);
 
   m_DataStorageDefaultListModel = new QmitkDataStorageDefaultListModel(this);
   m_DataStorageDefaultListModel->SetDataStorage(GetDataStorage());
   m_Controls.selectionListView->setSelectionMode(QAbstractItemView::ExtendedSelection);
   m_Controls.selectionListView->setSelectionBehavior(QAbstractItemView::SelectRows);
   m_Controls.selectionListView->setAlternatingRowColors(true);
   m_Controls.selectionListView->setModel(m_DataStorageDefaultListModel);
 
   m_DataStorageDefaultListModel2 = new QmitkDataStorageDefaultListModel(this);
   m_DataStorageDefaultListModel2->SetDataStorage(GetDataStorage());
   m_Controls.selectionListView2->setSelectionMode(QAbstractItemView::ExtendedSelection);
   m_Controls.selectionListView2->setSelectionBehavior(QAbstractItemView::SelectRows);
   m_Controls.selectionListView2->setAlternatingRowColors(true);
   m_Controls.selectionListView2->setModel(m_DataStorageDefaultListModel2);
 
   m_Controls.singleSlot->SetDataStorage(GetDataStorage());
   m_Controls.singleSlot->SetEmptyInfo(QString("EmptyInfo: Set this to display info in empty state"));
   m_Controls.singleSlot->SetInvalidInfo(QString("InvalidInfo: is displayed for invalid states"));
   m_Controls.singleSlot->SetPopUpTitel(QString("This is the definable caption. Choose your data now!"));
   m_Controls.singleSlot->SetPopUpHint(QString("I am an optional hint, that can be set by the developer<p/>If not set the widget is invisible."));
 
   m_Controls.multiSlot->SetDataStorage(GetDataStorage());
   m_Controls.multiSlot->SetEmptyInfo(QString("EmptyInfo: Set this to display info in empty state"));
   m_Controls.multiSlot->SetInvalidInfo(QString("InvalidInfo: is displayed for invalid states"));
   m_Controls.multiSlot->SetPopUpTitel(QString("This is the definable caption. Choose your data now!"));
   m_Controls.multiSlot->SetPopUpHint(QString("I am an optional hint, that can be set by the developer<p/>If not set the widget is invisible."));
 
   m_ModelViewSelectionConnector = std::make_unique<QmitkModelViewSelectionConnector>();
   try
   {
     m_ModelViewSelectionConnector->SetView(m_Controls.selectionListView);
   }
   catch (mitk::Exception& e)
   {
     mitkReThrow(e) << "Cannot connect the model-view pair signals and slots.";
   }
   m_SelectionServiceConnector = std::make_unique<QmitkSelectionServiceConnector>();
 
   m_ModelViewSelectionConnector2 = std::make_unique<QmitkModelViewSelectionConnector>();
   try
   {
     m_ModelViewSelectionConnector2->SetView(m_Controls.selectionListView2);
   }
   catch (mitk::Exception& e)
   {
     mitkReThrow(e) << "Cannot connect the model-view pair signals and slots.";
   }
   m_SelectionServiceConnector2 = std::make_unique<QmitkSelectionServiceConnector>();
 
   m_SelectionServiceConnector3 = std::make_unique<QmitkSelectionServiceConnector>();
   m_SelectionServiceConnector4 = std::make_unique<QmitkSelectionServiceConnector>();
 
   connect(m_Controls.selectionProviderCheckBox, SIGNAL(toggled(bool)), this, SLOT(SetAsSelectionProvider1(bool)));
   connect(m_Controls.selectionProviderCheckBox2, SIGNAL(toggled(bool)), this, SLOT(SetAsSelectionProvider2(bool)));
 
   connect(m_Controls.selectionListenerCheckBox, SIGNAL(toggled(bool)), this, SLOT(SetAsSelectionListener1(bool)));
   connect(m_Controls.selectionListenerCheckBox2, SIGNAL(toggled(bool)), this, SLOT(SetAsSelectionListener2(bool)));
 
   connect(m_Controls.selectionProviderCheckBox3, SIGNAL(toggled(bool)), this, SLOT(SetAsSelectionProvider3(bool)));
   connect(m_Controls.selectionListenerCheckBox3, SIGNAL(toggled(bool)), this, SLOT(SetAsSelectionListener3(bool)));
 
   connect(m_Controls.checkOnlyVisible, SIGNAL(toggled(bool)), m_Controls.singleSlot, SLOT(SetSelectOnlyVisibleNodes(bool)));
   connect(m_Controls.checkOptional, SIGNAL(toggled(bool)), m_Controls.singleSlot, SLOT(SetSelectionIsOptional(bool)));
   connect(m_Controls.checkOnlyImages, SIGNAL(toggled(bool)), this, SLOT(OnOnlyImages(bool)));
 
   connect(m_Controls.selectionProviderCheckBox4, SIGNAL(toggled(bool)), this, SLOT(SetAsSelectionProvider4(bool)));
   connect(m_Controls.selectionListenerCheckBox4, SIGNAL(toggled(bool)), this, SLOT(SetAsSelectionListener4(bool)));
 
   connect(m_Controls.checkOnlyVisible_2, SIGNAL(toggled(bool)), m_Controls.multiSlot, SLOT(SetSelectOnlyVisibleNodes(bool)));
   connect(m_Controls.checkOptional_2, SIGNAL(toggled(bool)), m_Controls.multiSlot, SLOT(SetSelectionIsOptional(bool)));
   connect(m_Controls.checkOnlyImages_2, SIGNAL(toggled(bool)), this, SLOT(OnOnlyImages2(bool)));
+  connect(m_Controls.checkOnlyUneven, SIGNAL(toggled(bool)), this, SLOT(OnOnlyUneven(bool)));
 }
 
 void QmitkDataStorageViewerTestView::SetAsSelectionProvider1(bool checked)
 {
   if (checked)
   {
     m_SelectionServiceConnector->SetAsSelectionProvider(GetSite()->GetSelectionProvider().Cast<QmitkDataNodeSelectionProvider>().GetPointer());
     connect(m_ModelViewSelectionConnector.get(), SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), m_SelectionServiceConnector.get(), SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
   }
   else
   {
     m_SelectionServiceConnector->RemoveAsSelectionProvider();
     disconnect(m_ModelViewSelectionConnector.get(), SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), m_SelectionServiceConnector.get(), SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
   }
 }
 
 void QmitkDataStorageViewerTestView::SetAsSelectionListener1(bool checked)
 {
   if (checked)
   {
     m_SelectionServiceConnector->AddPostSelectionListener(GetSite()->GetWorkbenchWindow()->GetSelectionService());
     connect(m_SelectionServiceConnector.get(), SIGNAL(ServiceSelectionChanged(QList<mitk::DataNode::Pointer>)), m_ModelViewSelectionConnector.get(), SLOT(SetCurrentSelection(QList<mitk::DataNode::Pointer>)));
   }
   else
   {
     m_SelectionServiceConnector->RemovePostSelectionListener();
     disconnect(m_SelectionServiceConnector.get(), SIGNAL(ServiceSelectionChanged(QList<mitk::DataNode::Pointer>)), m_ModelViewSelectionConnector.get(), SLOT(SetCurrentSelection(QList<mitk::DataNode::Pointer>)));
 
   }
 }
 
 void QmitkDataStorageViewerTestView::SetAsSelectionProvider2(bool checked)
 {
   if (checked)
   {
     m_SelectionServiceConnector2->SetAsSelectionProvider(GetSite()->GetSelectionProvider().Cast<QmitkDataNodeSelectionProvider>().GetPointer());
     connect(m_ModelViewSelectionConnector2.get(), SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), m_SelectionServiceConnector2.get(), SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
   }
   else
   {
     m_SelectionServiceConnector2->RemoveAsSelectionProvider();
     disconnect(m_ModelViewSelectionConnector2.get(), SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), m_SelectionServiceConnector2.get(), SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
   }
 }
 
 void QmitkDataStorageViewerTestView::SetAsSelectionListener2(bool checked)
 {
   if (checked)
   {
     m_SelectionServiceConnector2->AddPostSelectionListener(GetSite()->GetWorkbenchWindow()->GetSelectionService());
     connect(m_SelectionServiceConnector2.get(), SIGNAL(ServiceSelectionChanged(QList<mitk::DataNode::Pointer>)), m_ModelViewSelectionConnector2.get(), SLOT(SetCurrentSelection(QList<mitk::DataNode::Pointer>)));
   }
   else
   {
     m_SelectionServiceConnector2->RemovePostSelectionListener();
     disconnect(m_SelectionServiceConnector2.get(), SIGNAL(ServiceSelectionChanged(QList<mitk::DataNode::Pointer>)), m_ModelViewSelectionConnector2.get(), SLOT(SetCurrentSelection(QList<mitk::DataNode::Pointer>)));
   }
 }
 
 void QmitkDataStorageViewerTestView::SetAsSelectionProvider3(bool checked)
 {
   if (checked)
   {
     m_SelectionServiceConnector3->SetAsSelectionProvider(GetSite()->GetSelectionProvider().Cast<QmitkDataNodeSelectionProvider>().GetPointer());
     connect(m_Controls.singleSlot, SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), m_SelectionServiceConnector3.get(), SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
   }
   else
   {
     m_SelectionServiceConnector3->RemoveAsSelectionProvider();
     disconnect(m_Controls.singleSlot, SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), m_SelectionServiceConnector3.get(), SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
   }
 }
 
 void QmitkDataStorageViewerTestView::SetAsSelectionListener3(bool checked)
 {
   if (checked)
   {
     m_SelectionServiceConnector3->AddPostSelectionListener(GetSite()->GetWorkbenchWindow()->GetSelectionService());  
     connect(m_SelectionServiceConnector3.get(), &QmitkSelectionServiceConnector::ServiceSelectionChanged, m_Controls.singleSlot, &QmitkSingleNodeSelectionWidget::SetCurrentSelection);
   }
   else
   {
     m_SelectionServiceConnector3->RemovePostSelectionListener();
     disconnect(m_SelectionServiceConnector3.get(), &QmitkSelectionServiceConnector::ServiceSelectionChanged, m_Controls.singleSlot, &QmitkSingleNodeSelectionWidget::SetCurrentSelection);
   }
 }
 
 void QmitkDataStorageViewerTestView::SetAsSelectionProvider4(bool checked)
 {
   if (checked)
   {
     m_SelectionServiceConnector4->SetAsSelectionProvider(GetSite()->GetSelectionProvider().Cast<QmitkDataNodeSelectionProvider>().GetPointer());
     connect(m_Controls.multiSlot, SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), m_SelectionServiceConnector4.get(), SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
   }
   else
   {
     m_SelectionServiceConnector4->RemoveAsSelectionProvider();
     disconnect(m_Controls.multiSlot, SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), m_SelectionServiceConnector4.get(), SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
   }
 }
 
 void QmitkDataStorageViewerTestView::SetAsSelectionListener4(bool checked)
 {
   if (checked)
   {
     m_SelectionServiceConnector4->AddPostSelectionListener(GetSite()->GetWorkbenchWindow()->GetSelectionService());
     connect(m_SelectionServiceConnector4.get(), &QmitkSelectionServiceConnector::ServiceSelectionChanged, m_Controls.multiSlot, &QmitkMultiNodeSelectionWidget::SetCurrentSelection);
   }
   else
   {
     m_SelectionServiceConnector4->RemovePostSelectionListener();
     disconnect(m_SelectionServiceConnector4.get(), &QmitkSelectionServiceConnector::ServiceSelectionChanged, m_Controls.multiSlot, &QmitkMultiNodeSelectionWidget::SetCurrentSelection);
   }
 }
 
 void QmitkDataStorageViewerTestView::OnOnlyImages(bool checked)
 {
   if (checked)
   {
     m_Controls.singleSlot->SetNodePredicate(mitk::NodePredicateDataType::New("Image"));
   }
   else
   {
     m_Controls.singleSlot->SetNodePredicate(nullptr);
   }
 };
 
 void QmitkDataStorageViewerTestView::OnOnlyImages2(bool checked)
 {
   if (checked)
   {
     m_Controls.multiSlot->SetNodePredicate(mitk::NodePredicateDataType::New("Image"));
+    m_Controls.multiSlot->SetInvalidInfo(QString("InvalidInfo: is displayed for invalid states. Only images allowed!"));
   }
   else
   {
     m_Controls.multiSlot->SetNodePredicate(nullptr);
+    m_Controls.multiSlot->SetInvalidInfo(QString("InvalidInfo: is displayed for invalid states"));
   }
 };
+
+void QmitkDataStorageViewerTestView::OnOnlyUneven(bool checked)
+{
+  if (checked)
+  {
+    auto checkFunction = [](const QmitkMultiNodeSelectionWidget::NodeList & nodes)
+    {
+      if (!(nodes.size() % 2))
+      {
+        std::stringstream ss;
+        ss << "<font class=\"warning\"><p>Invalid selection.<p/><p>The number of selected nodes must be even! the current number is " << nodes.size() << ".</p>";
+        return ss.str();
+      }
+      return std::string();
+    };
+
+    m_Controls.multiSlot->SetSelectionCheckFunction(checkFunction);
+  }
+  else
+  {
+    auto checkFunction = [](const QmitkMultiNodeSelectionWidget::NodeList & nodes)
+    {
+      return std::string();
+    };
+
+    m_Controls.multiSlot->SetSelectionCheckFunction(checkFunction);
+  }
+};
\ No newline at end of file
diff --git a/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestView.h b/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestView.h
index ce4042ae3e..157775f528 100644
--- a/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestView.h
+++ b/Plugins/org.mitk.gui.qt.datastorageviewertest/src/internal/QmitkDataStorageViewerTestView.h
@@ -1,77 +1,78 @@
 /*===================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical Image Computing.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 #ifndef QMITKDATASTORAGEVIEWERTESTVIEW_H
 #define QMITKDATASTORAGEVIEWERTESTVIEW_H
 
 // mitk gui qt common plugin
 #include <QmitkAbstractView.h>
 #include "QmitkModelViewSelectionConnector.h"
 #include "QmitkSelectionServiceConnector.h"
 
 // data storage viewer test plugin
 #include "ui_QmitkDataStorageViewerTestControls.h"
 
 // qt widgets module
 #include "QmitkDataStorageDefaultListModel.h"
 
 /**
 * @brief DataStorageViewerTestView
 */
 class QmitkDataStorageViewerTestView : public QmitkAbstractView
 {
   Q_OBJECT
 
 public:
 
   static const std::string VIEW_ID;
 
 protected:
 
   virtual void SetFocus() override;
 
   virtual void CreateQtPartControl(QWidget* parent) override;
 
 private Q_SLOTS:
 
   void SetAsSelectionProvider1(bool checked);
   void SetAsSelectionProvider2(bool checked);
   void SetAsSelectionProvider3(bool checked);
   void SetAsSelectionProvider4(bool checked);
   void SetAsSelectionListener1(bool checked);
   void SetAsSelectionListener2(bool checked);
   void SetAsSelectionListener3(bool checked);
   void SetAsSelectionListener4(bool checked);
 
   void OnOnlyImages(bool checked);
   void OnOnlyImages2(bool checked);
+  void OnOnlyUneven(bool checked);
 
 private:
 
   Ui::QmitkDataStorageViewerTestControls m_Controls;
   QmitkDataStorageDefaultListModel* m_DataStorageDefaultListModel;
   QmitkDataStorageDefaultListModel* m_DataStorageDefaultListModel2;
 
   std::unique_ptr<QmitkModelViewSelectionConnector> m_ModelViewSelectionConnector;
   std::unique_ptr<QmitkSelectionServiceConnector> m_SelectionServiceConnector;
   std::unique_ptr<QmitkModelViewSelectionConnector> m_ModelViewSelectionConnector2;
   std::unique_ptr<QmitkSelectionServiceConnector> m_SelectionServiceConnector2;
 
   std::unique_ptr<QmitkSelectionServiceConnector> m_SelectionServiceConnector3;
   std::unique_ptr<QmitkSelectionServiceConnector> m_SelectionServiceConnector4;
 };
 
 #endif // QMITKDATASTORAGEVIEWERTESTVIEW_H