Listview data binding question

Question

Hi,

I have created a listview and I have bound it to ObservableCollection(Of UserInfo) list. The listview has 2 columns and I have bound the columns to properties in my object. When I add items to the collection I see them in my listview but the SourceUpdate event never gets fired. Is there anything specially needs to be done to get the event fired. I need to do more stuff once the user added to the list. Some code snippet below

XAML:
                <ListView ItemsSource="{Binding Source={StaticResource UsersListDataSource}, NotifyOnSourceUpdated=true}" IsSynchronizedWithCurrentItem="True" Margin="4,9,5,9" Name="lvUserList" SelectionMode="Single" SelectionChanged="OnListViewSelectionChanged" SourceUpdated="OnSourceUpdated" TargetUpdated="OnTargetUpdated">
                    <ListView.View>
                        <GridView>
                            <GridViewColumn DisplayMemberBinding="{Binding Path=UserName, Mode=OneWay}" Width="158" Header="User Name"/>
                            <GridViewColumn DisplayMemberBinding="{Binding Path=UserType, Mode=OneWay}" Width="158" Header="Autority Level"/>
                        </GridView>
                    </ListView.View>
                </ListView>

Answer 1

Try hooking into the ObservableCollections CollectionChanged event.

Regards,

Matt

Answer 2

Thanks Matt, It is already using ObservableCollection. I have been trying all I know to get an event once the collection changes whether an addition user has been added or deleted or modified but I don't seem to be doing it right because I dont get SourceUpdated event fired off. Below is the collection code. I can post more of my code if it helps more.

Public Class UsersList
   Inherits ObservableCollection(Of UserInfo)
   Private bolIsModified As Boolean

   Public Sub New()
      Dim strarrUserName() As String = Nothing
      Dim strarrPassword() As String = Nothing
      Dim strarrUserType() As String = Nothing
      Dim bolarrReserved() As Boolean = Nothing

      Try
         GetUserList(strarrUserName, strarrPassword, strarrUserType, bolarrReserved)

         For intCounter As Integer = 0 To strarrUserName.Length - 1
            MyBase.Add(New UserInfo(strarrUserName(intCounter), strarrPassword(intCounter), strarrUserType(intCounter), bolarrReserved(intCounter)))
         Next intCounter

      Catch ex As Exception

      End Try

   End Sub

Answer 3

You should be right to do something like this...  

public partial class Window1 : Window

    {

        public Window1()

        {

            InitializeComponent();

            this.Loaded += new RoutedEventHandler(Window1_Loaded);

        }

        void Window1_Loaded(object sender, RoutedEventArgs e)

        {

            ObservableCollection<string> myStrings = new ObservableCollection<string>();

            myStrings.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(myStrings_CollectionChanged);

            myStrings.Add("Item 1");

            myStrings.Add("Item 2");

            myStrings.Remove("Item 2");

        }

        void myStrings_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)

        {

            // This gets called when items are added or deleted from the ObservableCollection

            if (e.NewItems != null)

            {

                foreach (string s in e.NewItems)

                {

                    Console.WriteLine(string.Format("Item added : {0}", s));

                }

            }

            if (e.OldItems != null)

            {

                foreach (string s in e.OldItems)

                {

                    Console.WriteLine(string.Format("Item removed : {0}", s));

                }

            }

        }

    }

Warm regards,

Matt

P.S Sorry for the late response!

Answer 4

Hi,

since you inherit from PbservableCollection, you can override InsertItem and RemoveItem so that you're notfied properly when items are added or removed. Also, the constructor should probably call MyBase.New. And, FWIW, Beth Massi has demonstrated a how-to-video on utilizing ObservableCollections resp. inheriting from it using VB.net. I don't recall exactly what video it was, but it was either the WPF over data or the  WPF over Entity Framework series.

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Cheers,
Olaf

Answer 5

What are you actually trying to achieve and why would you want to subscribe to the Changed event at all? Why not just looping the UsersListDataSource at the end of the window or control lifecycle?

Also, your binding can be somewhat simpler:

Code-behind:

ObservableCollection<UserInfo> userCollection = new ObservableCollection<UserInfo>();
// Fill your collection here, or somewhere else
Resources["MyUserCollection"] = userCollection;

Xaml:

<ListView ItemsSource="{DynamicResource MyUserCollection}" >
    <ListView.View>
        <GridView>
            <GridViewColumn DisplayMemberBinding="{Binding Path=UserName, Mode=OneWay}" Width="158" Header="User Name"/>
            <GridViewColumn DisplayMemberBinding="{Binding Path=UserType, Mode=OneWay}" Width="158" Header="Autority Level"/>
        </GridView>
    </ListView.View>
</Listview>

Saves you some typing.

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Geert van Horrik - CatenaLogic
Visit my blog: http://blog.catenalogic.com

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