WPF Xaml processing order - wpf

Question

I have a simple address form for a customer. The country and state combo boxes are linked to ListCollectionViews. This is so when the user changes the country settings, the state list can be filtered in the model view. The problem is that when the form loads some previous information, the state combo box is blank even through it has data. It seems to be because of the order in they are placed in the xaml. If I put the country combo box before the state, if works fine, but I would like the country to come after the state. Is there a way I can leave the xaml layout the way it is, but have the country combo box processed before the state?
Xaml:
<StackPanel Orientation="Horizontal">
<TextBlock Height="23" Name="tbkMailState" Text="State/Province:" Width="80" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="2" Foreground="Black" />
<ComboBox Height="23" Name="cmbMailState" Width="200" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="2" Foreground="Black" ItemsSource="{Binding GeoStateListMail}" SelectedValue="{Binding OpenEntityListing.EntityMailAddress.GeoState_Id}" DisplayMemberPath="Name" SelectedValuePath="Id" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Height="23" Name="tbkMailCountry" Text="Country:" Width="80" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="2" Foreground="Black" />
<ComboBox Height="23" Name="cmbMailCountry" Width="200" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="2" Foreground="Black" ItemsSource="{Binding GeoCountryListMail, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" SelectedValue="{Binding OpenEntityListing.EntityMailAddress.GeoCountry_Id}" DisplayMemberPath="Name" SelectedValuePath="Id" IsSynchronizedWithCurrentItem="True" />
</StackPanel>
ViewModel filter:
public void GeoCountry_CurrentChanged(object sender, EventArgs e)
{
GeoStateList.Filter = item =>
{
GeoState vitem = item as GeoState;
if ((OpenEntityListing == null) || (vitem == null))
{
return false;
}
return vitem.GeoCountry_Id == OpenEntityListing.EntityAddress.GeoCountry_Id;
};
}

Answer 1

It would be bad to be dependent on the order of the xaml being processed.
Try to find a fitting event in your ViewModel when the ComboBox should be updated and bind the View to perhaps an extra property on the ViewModel.