How to bind observable collections to view number of items present in observable collection?

Question

Hi everyone i am working on a project which is configuring a networking device via telnet,i am using C# Wpf. The problem is i have a Observable Collection and i want to display number of items present in the observable collection but it is not displaying . I have tried following :

 public ObservableCollection<VLANSPropertyClass> vlan { get; set; }

  public int Vlans
        {
            // Retreive value from Configuration Library
            get
            {
                return this.vlan.Count;

            }
        }

XAML is :

 <TextBlock Margin="3,0"  
        Style="{StaticResource SummaryValues}"  
        Text="{Binding Path=Vlans}"
        Visibility="Visible"
        />

Now it is not displaying anything .Any help would be highly appreciable :)

Is vlan created before that Vlans get is called? Have you debugged and seen that line called. — paparazzo, Dec 08 '14 at 14:07

Theodosius Von Richthofen · Accepted Answer · 2014-12-08T15:17:29.937

3

Easiest is to simply bind to vlan.Count (in my example i used textbox, but textBlock won't need OneWay). No extra property or INotifyPropertyChanged needed. Adding to the collection will update the count automatically.

<TextBox Text="{Binding vlan.Count, Mode=OneWay}" />

or

<TextBlock Text="{Binding vlan.Count}" />

edited Dec 08 '14 at 15:17

answered Dec 08 '14 at 14:15

Theodosius Von Richthofen

2,441
1
21
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But why use a TextBox? Better use a TextBlock. Then there is also no need to specify `Mode=OneWay`. – Clemens Dec 08 '14 at 14:55
use whatever control you want, the point is just bind to the collection's count. this was just an example – Theodosius Von Richthofen Dec 08 '14 at 15:15
The textblock is not displaying anything ,it is displaying number of counts in back end console but not displaying in my view. – CodeTheft Dec 09 '14 at 06:57

score 1 · Answer 2 · answered Dec 08 '14 at 14:00

1

The binding does not know when to update the target. You need to implement INotifyPropertyChanged, subscribe to .CollectionChanged and raise a PropertyChanged event when Vlans (the count) changes.

answered Dec 08 '14 at 14:00

James Willock

1,999
14
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Yes i know how to do that? – CodeTheft Dec 08 '14 at 14:02

score 0 · Answer 3 · answered Dec 08 '14 at 14:10

You can use a ListCollectionView on top of the ObservableCollection.

In your ViewModel, define them as:

    ObservableCollection<VLANSPropertyClass> vlan;
    public System.Windows.Data.ListCollectionView CountingView { get; private set; }

Then, initialize the collection to the ObservableCollection:

CountingView = new System.Windows.Data.ListCollectionView(vlan);

In your xaml, bind to the Count property of the collection:

<TextBlock Margin="5" Height="35" Width="50" Text="{Binding CountingView.Count}" />

I hope this helps!

How to bind observable collections to view number of items present in observable collection?

3 Answers3