When i used databind with mvvm i got this exception

>org.zkoss.zk.ui.UiException: Listitem's parent must be Listbox, not <Chosenbox cRyP7>
>> at org.zkoss.zul.Listitem.beforeParentChanged(Listitem.java:339)
>> at org.zkoss.zk.ui.AbstractComponent.setParent(AbstractComponent.java:970)
>> at org.zkoss.zk.ui.AbstractComponent.insertBefore(AbstractComponent.java:1110)
>> at org.zkoss.zk.ui.impl.AbstractUiFactory.newComponent(AbstractUiFactory.java:100)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.execCreateChild0(UiEngineImpl.java:801)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.execCreateChild(UiEngineImpl.java:770)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.execCreate0(UiEngineImpl.java:679)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.access$800(UiEngineImpl.java:86)
>> at org.zkoss.zk.ui.impl.UiEngineImpl$TemplateImpl.create(UiEngineImpl.java:2163)
>> at org.zkoss.zkmax.bind.impl.BindChosenboxRenderer.render(BindChosenboxRenderer.java:70)
>> at org.zkoss.zkmax.zul.Chosenbox.prepareItems(Chosenbox.java:571)
>> at org.zkoss.zkmax.zul.Chosenbox.prepareData(Chosenbox.java:530)
>> at org.zkoss.zkmax.zul.Chosenbox.onInitRender(Chosenbox.java:700)
>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>> at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
>> at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
>> at java.lang.reflect.Method.invoke(Unknown Source)
>> at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2718)
>> at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2648)
>> at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:136)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1709)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1494)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage0(UiEngineImpl.java:463)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage(UiEngineImpl.java:316)
>> at org.zkoss.zk.ui.http.DHtmlLayoutServlet.process(DHtmlLayoutServlet.java:215)
>> at org.zkoss.zk.ui.http.DHtmlLayoutServlet.doGet(DHtmlLayoutServlet.java:135)
>> at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
>> at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
>> at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:306)
>> at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
>> at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
>> at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
>> at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
>> at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
>> at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:550)
>> at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
>> at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:380)
>> at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243)
>> at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
>> at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166)
>> at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:288)
>> at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
>> at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
>> at java.lang.Thread.run(Unknown Source)