Problem with VBox or Vertical layout

Hi Experts,

I have a page in which I have a subheader containing two combobox for which data is getting populated from models.

But then after I used VBOX/VerticalLayout under Subheader then i am not getting values for second comboBox. Although when i used HBOX or HorizontalLayout both the combobox are working fine.

Please find my view.XML file below:

<core:View xmlns:core="sap.ui.core"

xmlns:mvc="sap.ui.core.mvc"

xmlns:l = "sap.ui.layout"

xmlns="sap.m" controllerName="view.View1"

xmlns:html="http://www.w3.org/1999/xhtml">

<Page title="Timesheet">

<headerContent>

<Label text = "Dhiraj"></Label>

</headerContent>

<subHeader>

<Toolbar height ="8rem" >

<l:VerticalLayout>

<ComboBox id ="idComboBox" items="{dmodel>/ProductCollection}">

<core:Item key="{dmodel>Productid}" text="{dmodel>Name}" />

</ComboBox>

<ComboBox id ="idComboBox1" items="{lmodel>/Location}">

<core:Item key="{lmodel>locid}" text="{lmodel>locname}" />

</ComboBox>

</l:VerticalLayout>

</Toolbar>

</subHeader>

<content>

</content>

</Page>

</core:View>

I want to know what is the reason only one combobox is working when i am working with VBOX.

Thank You in advance..

Regards,

Dhiraj More