We Keep Coding

Remove ListBoxItem from ViewModel

I develop CRUD app for WindowsPhone 8.1. I can add data to ObservableCollection collection and this data is displayed on ListBox. I use MVVM pattern.
Full repository https://github.com/OlegZarevych/CRUD_WP81
View :
<ListBox x:Name="Storage" ItemsSource="{Binding Path=Models, Mode=TwoWay}" >
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Height="30" Width="450">
<TextBlock x:Name="nameblock" Text="{Binding Name}" />
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
And ViewModel class
public class ViewModel
{
public string NewName { get; set; }
public string NewSurname { get; set; }
public int NewAge { get; set; }
public int i=0 ;
public ObservableCollection<DataStorageModel> Models { get; set; }
//Event Handlers
public ICommand CreateClickCommand { get; set; }
public ICommand UpdateClickCommand { get; set; }
public ICommand DeleteClickCommand { get; set; }
public ViewModel()
{
CreateClickCommand = new RelayCommand(arg => CreateClickMethod());
UpdateClickCommand = new RelayCommand(arg => UpdateClickMethod());
DeleteClickCommand = new RelayCommand(arg => DeleteClickMethod());
Models = new ObservableCollection<DataStorageModel>() {};
}
private void CreateClickMethod()
{
Models.Add(new DataStorageModel() { Name = NewName, Surname = NewSurname, Age = NewAge, Count=i++ });
}
private void UpdateClickMethod()
{}
private void DeleteClickMethod()
{}
}
I want to change data and delete it. As i good understand, I need select count from ListBoxItems and delete(update) this count in ObservableCollection.
How can I work with XAML code from ViewModel class ?
How can I initiliaze Storage in ViewModel ?
Or in MVVM is the better way to resolve this problem ?

When you want to delete a model from the ListBox you typically need some way to identify the selected ListBoxItems (or models) that you want to delete; for that, consider having an IsSelected property on your models and bind it to a CheckBox inside the ListBoxItem data template.
Now, when you click on delete, the delete command can then easily look into the Models list and see which items are selected for deletion. After it deletes the items, it can then enumerate over the collection and recalculate the count value for the remaining items and update the field in the view model.
So, you don't have to access the XAML to update the count of the models. If you make the count property mutable then you wouldn't have to reinitialize the storage after you delete items from the list.

I added code t the Model
private bool _isSelected;
public bool IsSelected
{
get { return _isSelected; }
set
{
if (_isSelected != value)
{
_isSelected = value;
OnPropertyChanged("IsSelected");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Also added checkbox with bindin to View.
<ListBox x:Name="Storage" Background="Gray" FontSize="14" ItemsSource="{Binding Path=Models, Mode=TwoWay}" >
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Height="60" Width="400" >
<CheckBox x:Name="checkbox" IsChecked="{Binding Path=IsSelected, UpdateSourceTrigger=PropertyChanged}" />
<TextBlock x:Name="nameblock" Text="{Binding Name}"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
But IsSelected var doesn't change when I check checkbox in item
Why ?

C# wpf listbox not updating from ObservableCollection

I'm trying to get the databinding I need to work with a ListBox.
I've parsed some data from a text file to a ObservableCollection<ViewModel> but the data isn't updating in the ListBox.
Here's some information:
The data which is written to from the parser:
class MainData
{
private static ObservableCollection<GroupViewModel> groupModelList = new ObservableCollection<GroupViewModel>();
public static ObservableCollection<GroupViewModel> GroupModelList
{
get { return groupModelList; }
}
}
What GroupViewModel holds (not everything but it's all the same):
class GroupViewModel : INotifyPropertyChanged
{
private GroupModel groupModel;
public event PropertyChangedEventHandler PropertyChanged;
public GroupViewModel()
{
groupModel = new GroupModel();
}
public string Name
{
get { return groupModel.name; }
set
{
if (groupModel.name != value)
{
groupModel.name = value;
InvokePropertyChanged("Name");
}
}
}
...
}
And what GroupModel Holds:
class GroupModel
{
public string name { get; set; }
}
This is how the parser adds new items to the GroupModelView:
if (split[0] == "group")
{
currentGroup = new GroupViewModel();
currentGroup.Name = split[1];
MainData.GroupModelList.Add(currentGroup);
}
I created a ListBox in my WPF application with these XAML options:
<Window x:Class="SoundManager.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:SoundManager.ViewModels"
xmlns:vm2="clr-namespace:SoundManager.Code"
Title="MainWindow" Height="720" Width="1280">
<Window.Resources>
<vm:MainViewModel x:Key="MainViewModel" />
<vm2:MainData x:Key="MainData" />
</Window.Resources>
<ListBox Grid.Row="2" Height="484" HorizontalAlignment="Left" Margin="12,0,0,0" Name="lbFoundItems" VerticalAlignment="Top" Width="201" ItemsSource="{Binding Source={StaticResource MainData}, Path=GroupModelList/Name}" />
but for some reason the data isn't updating in the UI (new items aren't added visibly in the UI).
I've been just getting started with the MVVM pattern and databinding and I can't figure out what I'm doing wrong.
Thanks in advance!

GroupModelList/Name is not a valid property path here. Setting it like that does not make the ListBox show the Name property of the data items in the GroupModelList collection.
You would instead have to set the ListBox's DisplayMemberPath property:
<ListBox ItemsSource="{Binding Source={StaticResource MainData}, Path=GroupModelList}"
DisplayMemberPath="Name"/>
or set the ItemTemplate property:
<ListBox ItemsSource="{Binding Source={StaticResource MainData}, Path=GroupModelList}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Moreover, the GroupModelList property should not be static:
class MainData
{
private ObservableCollection<GroupViewModel> groupModelList =
new ObservableCollection<GroupViewModel>();
public ObservableCollection<GroupViewModel> GroupModelList
{
get { return groupModelList; }
}
}
Then you might have MainData as a property in your view model, and bind the ListBox like this:
<ListBox ItemsSource="{Binding Source={StaticResource MainViewModel},
Path=MainData.GroupModelList}" .../>

update style of selected item in tow way mode

i have a view that have a list view with data template
i need to set style on the selected item
but i need also when the selected item is been changed from the code it modify the selected item in the view
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="50" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Text="{Binding Text, UpdateSourceTrigger=PropertyChanged}" Width="300" Height="50" TextAlignment="Center"/>
<ListView Grid.Row="1" ItemsSource="{Binding List, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" SelectedItem="{Binding SelectedItem, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
<ListView.ItemTemplate>
<DataTemplate >
<Border BorderThickness="1" BorderBrush="White">
<Grid Height="20" Width="30" >
<TextBlock Text="{Binding Name}"/>
</Grid>
</Border>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
there is a list view and textblock
i need when the selectedItem changed it changed the the background of the selected item
here is the viewmodel
public class MainViewModel : ViewModelBase
{
private Item selectedItem;
public ObservableCollection<Item> List { get; set; }
string text;
public string Text
{
get { return text; }
set
{
text = value;
OnPropertyChanged("Text");
}
}
public Item SelectedItem
{
get { return selectedItem; }
set{
if (value.Name != "Test1")
{
selectedItem = value;
Text = value.Name;
}
else
{
Text = string.Format("Test1 was selected but the selected item is {0}", selectedItem==null?"null":selectedItem.Name);
}
OnPropertyChanged("SelectedItem");
}
}
public MainViewModel()
{
List = new ObservableCollection<Item>()
{
new Item("Test1","Val1"),new Item("Test2","Val2"),new Item("Test3","Val3"),new Item("Test4","Val"),
};
OnPropertyChanged("List");
}
}
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(params string[] propertyNames)
{
if (PropertyChanged != null)
{
foreach (var propertyName in propertyNames)
{
var e = new PropertyChangedEventArgs(propertyName);
PropertyChanged(this, e);
}
}
}
}
public class Item : ViewModelBase
{
public string Name { get; set; }
public string Value { get; set; }
public Item(string name, string val)
{
Name = name;
Value = val;
OnPropertyChanged("Name");
}
}
note that when the Test1 Item selected the selected item didnot changed but in the view Test1 is marked as selected

At the point your MainViewModel.SelectedItem setter is called by the view, the view has already updated its selected item in the list. The binding simply informs the VM of this fact. The fact that you don't set MainViewModel.selectedItem means nothing to the view.
You would think that raising OnPropertyChanged("SelectedItem"); would force the view to re-evaluate its selected item, but in practice this does not work. I assume is down to some optimization within WPF or to prevent cyclic binding updates. (Remember you setter is already being called as part of a binding update, and you are trying to update the binding again)
If you wish to prevent something being selected in the view, then you need to disable it within the view, before it gets down to the VM. Here is one way of doing this.

How to set SeletedItems = null in a Listbox if i select a other Listbox

basically i'm trying to do THIS
but you can see it is not MVVM so i'm looking for a way to set SeletedItems = null or clear() depending on what's doable
because in my View i will got N ListBoxes and if he pressed a Button after selecting some Items i will change some properties of the SeletedItems but only for the last active Listbox
so i decided to use on SelectedItems Property for all the Listboxes but it doesn't work based on 2 problems i can't bind to to SelectedItems and based on this i can't test how to remove the selection from the other Listboxes
EDIT:
to give you an simple example:
XAML
<Window x:Class="Test.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<ListBox Width="432" Height="67"
HorizontalAlignment="Left" VerticalAlignment="Top"
SelectionMode="Extended"
<!-- SeletedItems="{Binding SelectedListItems}" ??? -->
ItemsSource="{Binding Collection1}">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<TextBlock Text="{Binding MyText}"
Background="{Binding MyBackground}"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<ListBox Width="432" Height="67"
HorizontalAlignment="Left" VerticalAlignment="Top"
SelectionMode="Extended"
<!-- SeletedItems="{Binding SelectedListItems}" ??? -->
ItemsSource="{Binding Collection2}">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<TextBlock Text="{Binding MyText}"
Background="{Binding MyBackground}"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<Button Content="unselect" Width="80" Height="150"
HorizontalAlignment="Right" VerticalAlignment="Top"
Command="{Binding MyCommand}"/>
</StackPanel>
</Window>
Code
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows;
namespace Test
{
/// <summary>
/// Interaktionslogik für MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new VM();
}
}
public class VM : INotifyPropertyChanged
{
private ObservableCollection<DetailVM> _SelectedListItems = new ObservableCollection<DetailVM>();
public ObservableCollection<DetailVM> SelectedListItems
{
get { return _SelectedListItems; }
set
{
_SelectedListItems = value;
OnPropertyChanged("SelectedListItems");
}
}
public List<DetailVM> Collection1 { get; set; }
public List<DetailVM> Collection2 { get; set; }
private RelayCommand _myCommand;
public ICommand MyCommand
{
get { return _myCommand?? (_myCommand= new RelayCommand(param => OnMyCommand())); }
}
public void OnMyCommand()
{
foreach DetailVM item in SelectedListItems
{
item.MyBackground ="Red";
}
}
public VM()
{
Collection1 = new List<DetailVM>();
Collection2 = new List<DetailVM>();
for (int i = 0; i < 10; i++)
{
Collection1.Add(new DetailVM { MyText = "C1ITEM " + i });
Collection2.Add(new DetailVM { MyText = "C2ITEM " + i });
}
}
#region INotifyPropertyChanged Member
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
public class DetailVM
{
public string MyText { get; set; }
public string MyBackground { get; set; }
}
}
The code above should change the color of the Textbox background to Red
if the user selected some Items in a Listbox and he should only be able to seleted Items in one Listbox at the same time
so how to do this? (bear in mind this is a simple example but i need this for N Listboxes which will be generated over a template)

First of all, I would recommend you to extend ListView so that it includes a bindable SelectedValues property (you cannot use the name SelectedItems since it's already a non-bindable property of ListView). Here's an example of how this can be achieved.
public class MultiSelectListView : ListView
{
// Using a DependencyProperty as backing store
public static readonly DependencyProperty SelectedValuesProperty =
DependencyProperty.Register("SelectedValues", typeof(IList), typeof(MultiSelectListView), new PropertyMetadata(default(IList), OnSelectedItemsChanged));
public IList SelectedValues
{
get { return (IList)GetValue(SelectedValuesProperty); }
set { SetValue(SelectedValuesProperty, value); }
}
private static void OnSelectedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// if selected items list implements INotifyCollectionChanged, we subscribe to its CollectionChanged event
var element = (MultiSelectListView)d;
if (e.OldValue != null && e.OldValue is INotifyCollectionChanged)
{
var list = e.OldValue as INotifyCollectionChanged;
list.CollectionChanged -= element.OnCollectionChanged;
}
if (e.NewValue is INotifyCollectionChanged)
{
var list = e.NewValue as INotifyCollectionChanged;
list.CollectionChanged += element.OnCollectionChanged;
}
}
// when selection changes in the view, elements are added or removed from the underlying list
protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
if (SelectedValues != null)
{
foreach (var item in e.AddedItems)
{
if (!SelectedValues.Contains(item))
SelectedValues.Add(item);
}
foreach (var item in e.RemovedItems)
{
if (SelectedValues.Contains(item))
SelectedValues.Remove(item);
}
}
base.OnSelectionChanged(e);
}
// when underlying list changes, we set the control's selected items to the contents of the list
void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (SelectedValues != null)
{
SetSelectedItems(SelectedValues);
}
}
}
Once you've done this you can control the behavior of a list's selected items through the viewmodel. Clearing the viewmodel list clears the selected items in the control.
Next you can subscribe to the collection changed event of your selected items lists (in the view model) and in the handler check whether you need to clear any of your lists.

How to bind the view model to the view

I am having trouble binding my View Model to my View. I am a beginner with MVVM, but I believe I am implementing my system (almost) correctly. I have a Model that contains data, which I am getting in my View Model, and then when my page is navigated to, I am attempting to grab that View Model data and binding it to the View.
My issue is that I have a ListBox in my View with 3 objects per item, and I cannot seem to bind to it correctly for each item in my list.
MainPage.xaml
<ListBox x:Name="FavoritesListBox" ItemsSource="{Binding FavoriteItems}"
SelectionChanged="FavoritesListBox_SelectionChanged">
<StackPanel Orientation="Horizontal" Margin="12,0,12,0">
<Image x:Name="favicon" Source="{Binding Favicon}"
Width="50" Height="50"/>
<StackPanel>
<TextBlock x:Name="favoritesName" Text="{Binding Name}"
FontSize="{StaticResource PhoneFontSizeExtraLarge}"/>
<TextBlock x:Name="favoritesAddress"
Text="{Binding Address}" Margin="12,0,0,0"/>
</StackPanel>
</StackPanel>
</ListBox>
MainPage.xaml.cs
public FavoritesPage()
{
InitializeComponent();
// Set the data context of the listbox control to the sample data
FavoritesListBox.DataContext = App.ViewModel;
}
App.xaml.cs
private static MainViewModel viewModel = null;
public static MainViewModel ViewModel
{
get
{
// Delay creation of the view model until necessary
if (viewModel == null)
viewModel = new MainViewModel();
return viewModel;
}
}
MainViewModel.cs
public ObservableCollection<ItemViewModel> FavoriteItems { get; private set; }
public MainViewModel()
{
//FavoriteItems = new ObservableCollection<ItemViewModel>();
FavoriteItems = Settings.FavoritesList.Value;
}
Settings.cs (The Model)
public static Setting<ObservableCollection<ItemViewModel>> FavoritesList =
new Setting<ObservableCollection<ItemViewModel>>(
"Favorites",
new ObservableCollection<ItemViewModel>());
ItemViewModel.cs
private string _favicon;
public string Favicon
{
get
{
return _favicon;
}
set
{
if (value != _favicon)
{
_favicon = value;
NotifyPropertyChanged("Favicon");
}
}
}
private string _name;
public string Name
{
get
{
return _name;
}
set
{
if (value != _name)
{
_name = value;
NotifyPropertyChanged("Name");
}
}
}
private string _address;
public string Address
{
get
{
return _address;
}
set
{
if (value != _address)
{
_address = value;
NotifyPropertyChanged("Address");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
..and this is where and how I am saving each item (which should have three properties listed in the ItemViewModel
void addToFavorites_Click(object sender, EventArgs e)
{
var favoriteItem =
new ItemViewModel{
Favicon = "",
Name = "",
Address = TheBrowser.currentUrl() };
Settings.FavoritesList.Value.Add(favoriteItem);
}
Where FavoritesList is populated using an ItemViewModel containing 3 objects. The list is being populated correctly because during debugging I can see the entities in FavoritesList, but I am having an issue calling these entities in the view model to show up in my ListBox in the view?
I believe I am binding incorrectly but I'm not sure how to fix this?

In your XAML you bind to paths Name and Address do you have these 2 properties defined in your ItemViewModel?
Update after reading your code properly:
You are not updating the datatemplate of the Items of the Listbox. This is what you need to do:
<ListBox x:Name="FavoritesListBox" ItemsSource="{Binding FavoriteItems}" SelectionChanged="FavoritesListBox_SelectionChanged">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Margin="12,0,12,0">
<Image x:Name="favicon" Source="{Binding Favicon}" Width="50" Height="50"/>
<StackPanel>
<TextBlock x:Name="favoritesName" Text="{Binding Name}" FontSize="{StaticResource PhoneFontSizeExtraLarge}"/>
<TextBlock x:Name="favoritesAddress" Text="{Binding Address}" Margin="12,0,0,0"/>
</StackPanel>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

In addition to setting your DataContext to your viewmodel, (as mentioned in the comment linking to Creating ContextBinding XAML) , you also need to have your view model implement INotifyPropertyChanged (including ItemViewModel, which you don't show in your question)