Finding number of groups created with CollectionViewSource grouping

Question

I am having a list of messages and I am grouping them based on server(serverId) each message belongs to, like this -

<CollectionViewSource x:Key="MessageTypesByServer"
                      Source="{Binding MessageTypes, Mode=OneWay}">
    <CollectionViewSource.GroupDescriptions>
        <PropertyGroupDescription PropertyName="ServerId" />
    </CollectionViewSource.GroupDescriptions>
</CollectionViewSource>

and using a Group Style to display each group in a GroupBox like this -

<GroupBox Margin="0,0,0,3"
          Header="{Binding Name}">
   <ItemsPresenter />
</GroupBox>

Now, if the messages are from single server then I don't want to display the serverId in header of GroupBox, for doing this I need to find out the number of groups which are there in CollectionViewSource;

How can I do this in XAML? (I know I can find this is in my VM and hide/show header based on a property in VM etc. but I would like to do this in XAML).

Update:

I tried to use the CollectionViewSource.View like this -

<Style TargetType="{x:Type GroupBox}">
    <Setter Property="Header" Value="{Binding Name}" />

    <Style.Triggers>
        <DataTrigger Binding="{Binding View.Groups.Count, Source={StaticResource MessageTypesByServer}}"
                     Value="1">
            <Setter Property="Header" Value="No Server Name" />
        </DataTrigger>
    </Style.Triggers>
</Style>

but this doesn't work, View is always null(when seen in Snoop).

Update 2

I was able to get it working with a converter like this -

<DataTrigger Binding="{Binding Path=., Source={StaticResource MessageTypesByServer},  
    Converter={ValueConverters:CollectionViewSourceToGroupCountConverter}}"
             Value="1">
    <Setter Property="Header" Value="{x:Static System:String.Empty}" />
</DataTrigger>

and the converter logic -

ICollectionView view = value as ICollectionView;
if (view != null)
{
    return view.Groups.Count;
}

return 0;

although it is fine, I will be happy if I can do this without converter! Anyone having idea why the code in 1'st update doesn't work?

score 2 · Answer 1 · answered Sep 04 '12 at 08:28

2

You can bind to the CollectionViewSource and access the View.Groups property, which is an observable collection of groups -- cvs.View.Groups.Count is what you are after.

Do keep in mind that even when there is just one server involved the user should be able to somehow identify which one.

answered Sep 04 '12 at 08:28

Jon

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thanks, I was not able to find this; yes you are right but in my scenario server is a very technical detail and all clients won't need that, only few having multiple server need to know the server specific details. – akjoshi Sep 04 '12 at 12:35

Finding number of groups created with CollectionViewSource grouping

1 Answers1