myViewer.setSelection(new StructuredSelection(existingValue));
setSelectedValue(existingValue);
  public ComboViewerBinding(ComboViewer _viewer, EOModelObject _obj, String _propertyName, EOModelObject _listObj, String _listPropertyName) {    myViewer = _viewer;    myObj = _obj;    myPropertyName = _propertyName;    myListObj = _listObj;    myListPropertyName = _listPropertyName;    try {      Object existingValue = new Expression(myObj, MiscUtils.toGetMethod(myPropertyName, false), null).getValue();      myViewer.setSelection(new StructuredSelection(existingValue));    }    catch (Exception e) {      e.printStackTrace();    }    myViewer.addSelectionChangedListener(this);    myObj.addPropertyChangeListener(myPropertyName, this);    if (myListObj != null) {      myListObj.addPropertyChangeListener(myListPropertyName, this);    }  }