Develop Reference

C# BindingList<> not updating a WPF Listbox on changed items

I am on a MVVM C# project.
I want to display a list of objects.
I want to add and remove items in this list and ALSO change items in this list.
So I choosed the BindingList<> over the ObservableCollection<>, which would not get noticed if an item has changed.
(I also tested the ObservableCollectionEx which is out there in the web, but this has the same behavior like the BindingList for me).
But the Listbox is not changing when items are changed.
(Adding and removing items is updated in the Listbox)
In my XAML
<ListBox DisplayMemberPath="NameIndex" ItemsSource="{Binding Profiles}" SelectedItem="{Binding SelectedProfile}">
or alternative with the ItemTemplate
<ListBox DockPanel.Dock="Right" ItemsSource="{Binding Profiles}" SelectedItem="{Binding SelectedProfile}" Margin="0,10,0,0">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding NameIndex}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
In my ViewModel (ViewModelBase is implementing INotifyPropertyChanged etc)
public class ProfileListViewModel : ViewModelBase
{
private BindingList<Profile> profiles;
public BindingList<Profile> Profiles
{
get
{
return profiles;
}
set
{
profiles = value;
RaisePropertyChanged();
}
}
My items are also implementing INotifyPropertyChanged and I am calling OnPropertyChanged("Name") in my Setters.
My model
public class Profile : INotifyPropertyChanged
{
public Profile(){}
public int ProfileID { get; set; }
private string name;
public string Name
{
get
{
return name;
}
set
{
name = value;
OnPropertyChanged("Name");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Wiring the View with the ViewModel (BindingList is initialized before View)
ProfileListViewModel plvw= new ProfileListViewModel(message.Content);
var profileView = new ProfileListView(plvw);
profileView.ShowDialog();
In the View.xaml.cs
public ProfileListView(ProfileListViewModel plvw)
{
InitializeComponent();
DataContext = plvw;
}
When I am changing the name of an object then I get the ListChanged event to which I have subscribted in my ViewModel (Profiles.ListChanged += Profiles_ListChanged;) for testing BUT the items in the ListBox are NOT changing.
What am I doing wrong?
How can I get a updated Listbox?

Since your DisplayIndex is the computed property NameIndex, you need to call OnPropertyChanged("NameIndex") when its value changes due to a change in other properties, e.g.:
public string Name
{
get
{
return name;
}
set
{
name = value;
OnPropertyChanged("Name");
OnPropertyChanged("NameIndex");
}
}

Use
Profiles.ResetBindings() to bind it again.

WPF TwoWay binding in multiple UserControl

I have multiple UserControl which contain a shared ViewModel.
It's a DataGrid where the user click on a row to see the detail of the row (the actual structure is more complex).
The problem is when I handle the SelectionChanged in the grid, I update the shared ViewModel to update the ContactDetail but it doesn't update the value in the TextBoxes (the object is updated in ContactDetail but values are not displayed).
ListContact.xaml.cs
public void contactsTable_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
{
contacts.current_identity = //Get the associated `IdentityViewModel`
}
ContactDetail.xaml.cs
public partial class ContactDetail : UserControl
{
public ContactsViewModel contacts;
public DetailContact(ContactsViewModel contacts)
{
InitializeComponent();
this.contacts = contacts;
this.DataContext = contacts;
}
}
ContactDetail.xaml
<UserControl x:Class="ContactDetail">
<TextBox Name='address' Text="{Binding Path=contacts.current_identity.address, Mode=TwoWay}"/>
<TextBox Name='phone' Text="{Binding Path=contacts.current_identity.phone, Mode=TwoWay}"/>
<TextBox Name='email' Text="{Binding Path=contacts.current_identity.email, Mode=TwoWay}"/>
</UserControl>
ContactsViewModel.cs (IdentityViewModel uses the same structure)
public class ContactsViewModel : INotifyPropertyChanged
{
private List<Contact> _contacts;
public List<Contact> contacts;
{
get { return _contacts; }
set { _contacts = value; OnPropertyChanged("contacts"); }
}
private IdentityViewModel _current_identity;
public IdentityViewModel current_identity
{
get { return _current_identity; }
set { _current_identity = value; OnPropertyChanged("current_identity"); }
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
The question is, why doesn't this work and how to notify ContactDetail so that it displays the new value ?

Your data for contacts changes but the original reference location Binding Path=contacts.current_identity.address is still being referred to in the binding. I.E. address is still valid and has not changed. What changed was contacts.current but you are not binding to that.
Remember that binding is simply reflection to a location reference. If the original address changes you would see a change because that is what is being looked for to have a change. But instead the parent instance is what changed.
You need to refactor your bindings to allow for proper update when the current_identity changes.

Combo Box Binding Phone 8.1 UAP

How do i bind properly to a combox on windows phone 8.1 I tried what i would normally do in winforms but it didnt work. Also this is for a settings page is their any standard practise yet for a 8.1 Phone Store app to create a settings page same way silverlight did.
And before you ask yes the data is their fine have dubged that.
public class City
{
public string id { get; set; }
public string timing_title { get; set; }
}
public class CitysList
{
public List<City> cityList { get; set; }
}
I thought that DisplayMmember path would work when its set from item source
<ComboBox x:Name="cboCitys" ItemsSource="{Binding}" DisplayMemberPath="{Binding timing_title}" HorizontalAlignment="Left" Margin="18,73,0,0" VerticalAlignment="Top" Width="343" Height="51">
</ComboBox>
How i Fetech the data
popcornpk_Dal _dal = new popcornpk_Dal();
CitysList _mycities = await _dal.GetCityListAsync();
cboCitys.ItemsSource = _mycities.cityList;

DisplayMemberPath is used to specify the path to the displayed property, you don't need to bind it
DisplayMemberPath="timing_title"
beside that it would be much more elegant if you bind your combobox's itemSource to a Collection property, and implement the INotifyPropertyChanged in your CitysList class, like so :
public class CitysList:INotifyPropertyChanged
{
private ObservableCollection<City> _citylist ;
public ObservableCollection<City> CityList
{
get
{
return _citylist;
}
set
{
if (_citylist == value)
{
return;
}
_citylist = value;
OnPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
Xaml
<ComboBox ItemsSource="{Binding CitysList}" DisplayMemberPath="timing_title" />
and don't forget to set the DataContext to an instance of the class that hold the collection, and to update the List just reinstantiate it
CityList = new ObservableCollection<City>(await _dal.GetCityListAsync());
Update
To set the dataContext,
First Create a CityList property in the codebehind,
private CitysList _cityList ;
public CitysList CityList
{
get
{
return _cityList;
}
set
{
if (_cityList == value)
{
return;
}
_cityList = value;
OnPropertyChanged();
}
}
Second, set the page DataContext to the codebehind using
this.DataContext=this; //in the main constructor
or from Xaml using
DataContext="{Binding RelativeSource={RelativeSource Self}}"
the Combobox will automatically inherit the page DataContext
Third Bind to your collection
<ComboBox x:Name="cboCitys" ItemsSource="{Binding CityList.CityList}" DisplayMemberPath="timing_title" HorizontalAlignment="Left" Margin="18,73,0,0" VerticalAlignment="Top" Width="343" Height="51">
PS: you may as well consider adding the CityList collection directly in your codebehind there are no need to add a class just to hold that collection !

Binding ObservableCollection in viewmodel to listbox

I'm very new to MVVM and bindings and I'm trying to learn to work with it.
I run into the problem of binding my viewmodel to the view in particular binding an observable collection to a listbox.
this is what my viewmodel looks like:
namespace MyProject
{
using Model;
public class NetworkViewModel: INotifyPropertyChanged
{
private ObservableCollection<Person> _networkList1 = new ObservableCollection<Person>();
public ObservableCollection<Person> NetworkList1 //Binds with the listbox
{
get { return _networkList1; }
set { _networkList1 = value; RaisePropertyChanged("_networkList1"); }
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public NetworkViewModel()
{
_networkList1 = new ObservableCollection<Person>()
{
new Person(){FirstName="John", LastName="Doe"},
new Person(){FirstName="Andy" , LastName="Boo"}
};
}
}
in the view I have
namespace MyProject
{
public partial class Networking : Window
{
public Networking()
{
InitializeComponent();
this.DataContext = new NetworkViewModel();
lb1.ItemsSource = _networkList1;
}
}
}
and in the XAML I have
<ListBox x:Name="lb1" HorizontalAlignment="Left" ItemsSource="{Binding NetworkList1}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock >
<Run Text="{Binding Path=FirstName}"/>
<Run Text="{Binding Path=LastName}"/>
</TextBlock>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

It seems like you might have a typo in your view model.
RaisePropertyChanged("_networkList1");
You want to raise the property changed notification for the public property not the private variable.
RaisePropertyChanged("NetworkList1");
This might be preventing your view from updating properly.

In addition to Gaurav answer, if _networkList1 is a private field in your NetworkViewModel class, how is it possible to get access to it in Networking window? I mean what's the meaning of the following line?
lb1.ItemsSource = _networkList1;
when you define a Property (NetworkList1), you have to use it in order to get advantages of its features (e.g. to get RaisePropertyChanged working). Otherwise what's the point, you could have just defined a field (_networklist1). So changing
_networkList1 = new ObservableCollection<Person>()
to
NetworkList1 = new ObservableCollection<Person>()
results in actually setting NetworkList1 and therefore RaisePropertyChanged("NetworkList1") to be fired. (however if you want to just show data in a your listbox this is unnecessary)
and if i'm getting it right, changing this:
public partial class Networking : Window
{
public Networking()
{
InitializeComponent();
this.DataContext = new NetworkViewModel();
lb1.ItemsSource = _networkList1;
}
}
to
public partial class Networking : Window
{
public NetworkViewModel MyViewModel { get; set; }
public Networking()
{
InitializeComponent();
MyViewModel = new NetworkViewModel();
this.DataContext = MyViewModel;
}
}
should get your binding to work.
*Note that when you set DataContext to NetworkViewModel, then the binding in
<ListBox x:Name="lb1" HorizontalAlignment="Left" ItemsSource="{Binding NetworkList1}">
works, because NetworkList1 is a Property of NetworkViewModel.

Do not call RaisePropertyChanged() method on ObservableCollection<T>, for god's sake. This is a common mistake in a majority of cases (however, there are cases, where you need to reset ObservableCollection<T> using new keyword, but they are kinda rare).
This is a special type of collection which notifies UI internally about all the changes of its content (like add, remove etc.). What you need is to set the collection using new keyword once in a lifetime of your ViewModel, and then manipulate your items via Add(T item), Remove(T item), Clear() methods etc.
and UI will get notified about it and updated automatically.

Bind collection to combobox

I have this combobox
<ComboBox Height="30" SelectedIndex="0" Margin="5 3 5 3" Width="170" ItemsSource="{Binding WonderList}" SelectedValuePath="selectedWonder">
<ComboBox.ItemTemplate>
<DataTemplate>
<WrapPanel>
<Image Source="{Binding Path}" Height="20"></Image>
<Label Content="{Binding Name}" Style="{StaticResource LabelComboItem}"></Label>
</WrapPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
where I want to show items as an image plus a text.
This is the business class for the objects in the item list
public class Wonder: INotifyPropertyChanged
{
private string name;
private string path;
public event PropertyChangedEventHandler PropertyChanged;
#region properties, getters and setters
public String Name { get; set; }
public String Path { get; set; }
#endregion
public Wonder(string name, string path)
{
this.name = name;
this.path = path;
}
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
and the code behind of the window
public class Window1 {
public List<Wonder> WonderList;
public Window1()
{
InitializeComponent();
WonderList = new List<Wonder>();
WonderList.Add(new Wonder("Alexandria", "Resources/Images/Scans/Wonders/Alexandria.jpg"));
WonderList.Add(new Wonder("Babylon", "Resources/Images/Scans/Wonders/Babylon.jpg"));
}
}
I´m pretty new to this xaml "magic" and guess I dont understand correctly how the data binding works, I think that with ItemsSource="{Binding WonderList}" it should take the collection with that name (from the code behind) and show their Name and Path, but it shows an empty list.
If I do Combo1.ItemsSource = WonderList; in the code behind (I prefer to use the xaml and avoid the code behind), it shows two blank slots but still don´t know how to show the items.
Can you point me in the right direction?
Thanks

If you want to bind like this ItemsSource="{Binding WonderList}" you have to set the DataContext first.
public Window1()
{
...
this.DataContext = this;
}
Then Binding will find the WonderList in Window1 but only if it is a property too.
public List<Wonder> WonderList { get; private set; }
Next: It is useless to bind to property Name if you assign your value to private field name. Replace your constructor with
public Wonder(string name, string path)
{
this.Name = name;
this.Path = path;
}
Next: Your auto properties ({ get; set; }) will not notify for changes. For this you have to call OnPropertyChanged in setter. e.g.
public String Name
{
get { return name; }
set
{
if (name == value) return;
name = value;
OnPropertyChanged("Name");
}
}
Same thing for WonderList. If you create the List to late in constructor it could be all bindings are already resolved and you see nothing.
And finally use ObservableCollection if you want to notify not for a new list but a new added item in your list.

You are not doing the correct way. Simply saying, you should have a Wonders class holding an ObservableCollection property, which is bound to ComboBox's ItemsSource. You should read MSDN:
http://msdn.microsoft.com/en-us/library/ms752347.aspx