How to maintain viewstate for combobox after page postbacks?

[venu.sn2009]

Hi,

After selecting a list item in cmbUnitsOfMeasurement combobox , If an ext button is clicked(Autopostback="true") the selected ValueField is shown instead of DisplayField .

Thanks
venu

Html Source

<ext:Store runat="server" ID="stUOM" OnRefreshData="stUOM_RefreshData">
    <Proxy>
        <ext:PageProxy />
    </Proxy>
    <Reader>
        <ext:JsonReader>
            <Fields>
                <ext:RecordField Name="UomId" />
                <ext:RecordField Name="Description" />
            </Fields>
        </ext:JsonReader>
    </Reader>
    <AutoLoadParams>
        <ext:Parameter Name="start" Value="0" Mode="Raw" />
        <ext:Parameter Name="limit" Value="15" Mode="Raw" />
    </AutoLoadParams>
</ext:Store>
<ext:CompositeField ID="CompositeField1" runat="server" Width="250">
    <Items>
        <ext:ComboBox ID="cmbUnitsOfMeasurement" Width="230" runat="server" StoreID="stUOM" TypeAhead="false"
            FieldClass="Input-small"  MinChars="1" HideTrigger="true"
            DisplayField="Description" ValueField="UomId" ListClass="cb-list"
            MaxLength="50" LazyInit="false" ListWidth="300" PageSize="25">
            <Listeners>
                <AfterRender Handler="this.pageTb.refresh.hide();" />
            </Listeners>
        </ext:ComboBox>
        <ext:Label ID="Label4" runat="server" CtCls="ColorRed"  Text="*"/>
    </Items>
</ext:CompositeField>

code behind

protected void stUOM_RefreshData(object sender, StoreRefreshDataEventArgs e)
        {
            int count = 1;
            
            List<UnitsOfMeasurement> listItem = SearchUOM(out count);
            (stUOM.Proxy[0] as PageProxy).Total = count;
            cmbUnitsOfMeasurement.GetStore().DataSource = listItem;
            cmbUnitsOfMeasurement.GetStore().DataBind();
        }