P:selectOneMenu first ajax reuqest issue
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I have a problem with prime faces "selectOneMenu" component as i try to update " p:dataGrid " by change the SelectOneMenu value as follow :
   						
    <p:selectOneMenu value="#{bussinessOwnersViewerMB.selectedCity}" effect="explode"> 	           
        
	           <f:selectItems value="#{bussinessOwnersViewerMB.cities}" var="city" itemLabel="#{city.cityName}" itemValue="#{city.cityId}"/>  
	           <p:ajax listener="#{bussinessOwnersViewerMB.handleCityChange}" update="mainform:bolist"/>
        </p:selectOneMenu>
       		  
        <p:dataGrid id="bolist" var="bo" value="#{bussinessOwnersViewerMB.bOwners}" columns="3" rows="#{bussinessOwnersViewerMB.os}">

			<p:column>

				<p:panel header="#{bo.bOName}">

					<h:panelGrid columns="1">
						
						
							<p:graphicImage value="/resources/images/#{bo.boType}/#{bo.bOId}/mainProfile.jpg"/>
						
						

					</h:panelGrid>

				</p:panel>

			</p:column>

		</p:dataGrid>

The problem is when i change the selectOneMenu's value at the first time the datagrid doesn't updated what happen is only the postconstructor method is called after the first change it works fine .. 

my managed bean is viewscoped manage bean . 

and the listner method "bussinessOwnersViewerMB.handleCityChange" is : 


    public void handleCityChange(ValueChangeEvent event) {  
			  bOwners = bovb.loadAllDistributerByType(new Integer(selectedCity)); // selectedcity is the selected item id 
			  os = Integer.toString(bOwners.size());
}