Formatting the date in the DatePicker control within a Silverlight DataForm

This is driving me nuts!

I have a RIA Services driven dataform in silverlight which contains a datepicker control. I want to display the date in ddMMMyyyy format. Here is a sample of the xaml:

<dataFormToolkit:DataForm x:Name="dataForm" AutoGenerateFields="False">
                <dataFormToolkit:DataForm.EditTemplate>
                    <DataTemplate>
                        <StackPanel>
                            <dataFormToolkit:DataField Label="First Name">
                                <TextBox Text="{Binding PE_FIRST_NAME, Mode=TwoWay}"/>
                            </dataFormToolkit:DataField>
                            <dataFormToolkit:DataField Label="Surname">
                                <TextBox Text="{Binding PE_SURNAME_NAME,Mode=TwoWay}"/>
                            </dataFormToolkit:DataField>
                            <dataFormToolkit:DataField Label="Department">
                                <ComboBox x:Name="cboDepartment" DisplayMemberPath="CC_NAME" SelectedValuePath="CC_ID" SelectedValue="{Binding Path=CC_ID, Mode=TwoWay}"/>
                            </dataFormToolkit:DataField>
                            <dataFormToolkit:DataField Label="Start Date">
                                <controls:DatePicker Text="{Binding PE_START_DATE, Mode=TwoWay}"/>
                            </dataFormToolkit:DataField>
                        </StackPanel>
                    </DataTemplate>
                </dataFormToolkit:DataForm.EditTemplate>
           开发者_JAVA技巧 </dataFormToolkit:DataForm>
        </StackPanel>

I have followed the advice given in How to change date format in Silverlight DatePicker control? and added the following lines to my App startup:

Thread.CurrentThread.CurrentCulture = (CultureInfo)Thread.CurrentThread.CurrentCulture.Clone();
        Thread.CurrentThread.CurrentCulture.DateTimeFormat.ShortDatePattern = "ddMMMyyyy";

but it doesn't make any difference, the date always comes out in its raw format, e.g. 1/3/2006 12:00AM

Is there some reason why the current culture is not working in a dataform?

Update: If I implement the same form the hard way by not using a dataform then the date is in the correct format!

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controls:DatePicker Text="{Binding PE_START_DATE, Mode=TwoWay, StringFormat='d'}"

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You only have to add to the binding a StringFormat='MM/dd/yyyy' attribute.

<TextBox IsReadOnly="True" TextAlignment="Center" Text="{Binding AlbumDate, StringFormat='MM/dd/yyyy'}" />