Develop Reference

In wpf Clear ListBox items at Runtime

I am using wpf listbox, i cannot able to clear the list when am calling the reload data function, i just want to reload new data at runtime,while page loading it loads the data correctly, when i refresh the new data is fetched in itemsource i can see that in debug mode, but no new data in listbox, old data remains in the list, i cant even clear, when i call list.items.clear(), i tried lot ways, is there any problem in my XAML binding, the following is my code.
XAML:
<ListBox ItemsSource="{Binding}" HorizontalContentAlignment="Left" x:Name="lstbxindex" Foreground="White" FontSize="20px" Height="400" BorderBrush="#555555" Margin="10,34,16,0" VerticalAlignment="Top" Width="322" Background="#555555" >
<ListBox.ItemTemplate>
<DataTemplate>
<WrapPanel Orientation="Horizontal" Margin="5" >
<StackPanel Orientation="Horizontal">
<TextBlock x:Name="txtblckroundhour" Height="40px" Width="55px" Text="{Binding RoundedHours}" FontSize="14" Background="#555555" Loaded="txtblckroundhour_Loaded" Foreground="White"></TextBlock>
<Label x:Name="items" MouseDoubleClick="items_MouseDoubleClick" Content="{Binding ProjectRow.Name}" Background="#555555" FontSize="20" Loaded="items_Loaded" Visibility="Visible" Margin="35,0,0,0" Width="230" Foreground="White"></Label>
</StackPanel>
<StackPanel Orientation="Vertical">
<ComboBox Height="40px" Width="290" Margin="-230,0,0,0" Loaded="ComboBox_Loaded" Visibility="Hidden" IsEditable="True" FontSize="20" Background="White" Foreground="Black"></ComboBox>
</StackPanel>
<!--<ComboBox x:Name="ComboBox_AddItem" Height="40px" Width="290" Margin="-35,35,0,0" Loaded="ComboBox_AddItem_Loaded" IsEditable="True" FontSize="20" Background="White" Visibility="Hidden" Foreground="Black"></ComboBox>-->
</WrapPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Get the list of values
private List<ProjectInformation> projectInformationList1 = new List<ProjectInformation>();
// Here define the actual binding of the userinterface listbox to the in-memory list of objects.
foreach (DtoProjectsRow row in projectsTable.Rows)
{
projectInformationList1.Add(new ProjectInformation(row));
}
lstbxindex.DataContext = projectInformationList1;
In SO I tried some solution but unfortunately it is not work for me. Last I tried,
XAML.cs page
public static readonly DependencyProperty MyListProperty = DependencyProperty.Register("MyList", typeof(ObservableCollection<String>), typeof(Window));
public ObservableCollection<String> MyList
{
get
{
return (ObservableCollection<String>)GetValue(MyListProperty);
}
set
{
SetValue(MyListProperty, value);
}
}
XAML:
<ListBox ItemsSource="{Binding **ElementName=Window**}" HorizontalContentAlignment="Left" x:Name="lstbxindex" Foreground="White" FontSize="20px" Height="400" BorderBrush="#555555" Margin="10,34,16,0" VerticalAlignment="Top" Width="322" Background="#555555" >
Using this above solution listitems are clear but when pageloading the listboxitems are clear but I don't want to clear the iistboxitems, after updating the values from user it will reload the updated value in listbox.
lstbxindex.ItemsSource = null;
But its not work.For pageload listbox loaded all items,every 15 min interval it will call the load function for firsttime it will reload the updatedvalues but second time it will reload the updated values and previous values remains in listbox again.

I misunderstood initially thinking you were using MVVM, instead you're populating the ListView datasource from code behind.
Your line lstbxindex.DataContext = projectInformationList1; does not set the Data as you'd think. Instead try lstbxindex.DataContext = this; which means you're telling your view to look for the data source in code behind.
As such, I suggest adding using System.ComponentModel; and using BindingList, a comparison is here.
private BindingList<ProjectInformation> projectInformationList1 = new BindingList<ProjectInformation>();
And you just need this once:
foreach (DtoProjectsRow row in projectsTable.Rows)
{
projectInformationList1.Add(new ProjectInformation(row));
}
lstbxindex.DataSource = projectInformationList1;
As mentioned in the comments, if you did not use ItemsSource="{Binding projectInformationList1}" as I suggested in a comment to your question, this is the alternative:
private ObservableCollection<ProjectInformation> projectInformationList1 = new ObservableCollection<ProjectInformation>();
foreach (DtoProjectsRow row in projectsTable.Rows)
{
projectInformationList1.Add(new ProjectInformation(row));
}
lstbxindex.DataContext = projectInformationList1;

You should have a view model class with a collection property, e.g. like this:
public class ViewModel
{
public ObservableCollection<ProjectInformation> Projects { get; }
= new ObservableCollection<ProjectInformation>();
}
Set the DataContext of your Window or Page in XAML like this:
<Window.DataContext>
<local:ViewModel/>
</Window.DataContext>
and bind the ListBox like this:
<ListBox ItemsSource="{Binding Projects}">
...
</ListBox>
To clear all items in the source collection, access the DataContext in code behind:
var vm = (ViewModel)DataContext;
vm.Projects.Clear();
Edit: Instead of assigning the DataContext in XAML, you may as well do it in code behind, even before the Page or Window is initialized:
public MainWindow()
{
DataContext = new ViewModel();
InitializeComponent();
}

Added the line in loadfunction, Initially set null for ItemSource and then set null to the list object
lstbx.ItemsSource=null;
lstbx.Items.Clear();
ProjectInfoList1=null;
it will clear the listboxitems and reload with updated values only.
private BindingList<ProjectInfo> projectInfoList1 = new BindingList<ProjectInfo>();
Public void loadfunction()
{
lstbx.ItemsSource=null;
lstbx.Items.Clear();
ProjectInformationList1=null;
foreach (DtoProRow row in table.Rows)
{
projectInfoList1.Add(new ProjectInfo(row));
}
lstbx.DataContext = projectInfoList1;
}

How to get WPF ListBox to update at start using ItemsSource?

I am very new to WPF and especially to data-binding but I'm trying to populate a ListBox with elements from an external resource, and trying to also follow the MVVM pattern. As such I am trying to avoid any code in my code-behind. I've looked over dozens of other questions similar to this but I feel I am missing something stupid as I cannot get my ListBox to generate with values. I have set the DataContext and then set the Binding for the ItemsSource to the correct property.
Question
How do I simply get this code to populate my empty ListBox when the application starts up?
XAML
<TabItem Name="ServerListTab" Header="Server List">
<TabItem.DataContext>
<viewModel:ServerListViewModel />
</TabItem.DataContext>
<ListBox
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
ItemsSource="{Binding ServerList, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
IsSynchronizedWithCurrentItem="True"
SelectedItem="{Binding SelectedServer}">
</ListBox>
</TabItem>
ServerList property in view model
public BindingList<string> ServerList
{
get { return _serverListModel.ServerList; }
set
{
if (ReferenceEquals(_serverListModel.ServerList, value)) return;
var aTestServers = //code hidden : gets array correctly from resource
for (var i = 0; i < aTestServers.Count; i++)
{
_serverListModel.ServerList.Add(aTestServers[i]);
}
InvokePropertyChanged("ServerList");
}
}

secondary listbox not show data

i've two listbox binded with properties of my viewmodel, the first listbox shows LstEmpresas and work fine, when I select a item, the property SelectedCompany sets fine, all ok.
In SelectedCompany's set of my viewmodel, I call a method than pupulate a secondary list (LtsEjercicios) and work fine too (LtsEjercicios populate perfectly depends that item i've selected in the first listbox).
The secondary listbox binds his ItemSource from LtsEjercicios object that, across viewmodel, is updated.
But the secondary listbox NOT SHOW any data, i'm crazy yet.
This viewModel code
public class frmEmpresasVM : ViewModelBase
{
//propiedades
EmpresasDataAccess empresasController = new EmpresasDataAccess();
private ObservableCollection<EmpresasTable> lstEmpresas;
private ObservableCollection<EmpresasEjerciciosTable> ltsEjercicios;
public ObservableCollection<EmpresasTable> LstEmpresas
{
get
{
return lstEmpresas;
}
set
{
lstEmpresas = value; RaisePropertyChanged("LstEmpresas");
}
}
public ObservableCollection<EmpresasEjerciciosTable> LtsEjercicios
{
get
{
return ltsEjercicios;
}
set
{
ltsEjercicios = value; RaisePropertyChanged("LtsEjercicios");
}
}
//selected company in listbox
private int selectedCompany;
public int SelectedCompany
{
get
{
return selectedCompany;
}
set
{
selectedCompany = value;
LtsEjercicios = empresasController.SelectExercicesById(selectedCompany.ToString());
RaisePropertyChanged("SelectedCompany");
}
}
//main constructor, default values for lists
public frmEmpresasVM()
{
LstEmpresas = empresasController.SelectOnlyNames();
LtsEjercicios = empresasController.SelectExercicesById("0");
}
and, XAML for the view
<ListBox x:Name="companyList" HorizontalAlignment="Left" Height="205" Margin="20,30,0,0" VerticalAlignment="Top" Width="450" ItemsSource="{Binding LstEmpresas, Mode=OneWay}" SelectedValue="{Binding SelectedCompany, Mode=TwoWay}" SelectedItem="{Binding LtsEjercicios, Mode=OneWay}" SelectedIndex="0" DisplayMemberPath="Nombre" SelectedValuePath="Id" IsSynchronizedWithCurrentItem="True" SelectionChanged="companyList_SelectionChanged_1">
<ListBox.ItemBindingGroup>
<BindingGroup/>
</ListBox.ItemBindingGroup>
<ListBox.DataContext>
<InnovaCommerceHosteleryViewModels:frmEmpresasVM/>
</ListBox.DataContext>
</ListBox>
<TextBlock x:Name="lblEjercicio" HorizontalAlignment="Left" Height="20" Margin="475,10,0,0" TextWrapping="Wrap" Text="Ejercicios" VerticalAlignment="Top" Width="95"/>
<ListBox x:Name="excercicesList" HorizontalAlignment="Left" Height="205" Margin="475,30,0,0" VerticalAlignment="Top" Width="110" ItemsSource="{Binding LtsEjercicios, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="Ejercicio" SelectedValuePath="Id" SelectedIndex="0" IsSynchronizedWithCurrentItem="True">
<ListBox.DataContext>
<InnovaCommerceHosteleryViewModels:frmEmpresasVM/>
</ListBox.DataContext>
Al Data provides from a MySQL Database from both tables (empresas y empresas_ejercicios).
My goal is, when user select a item in listbox1 (empresas) show exercices in listbox2 (empresas_ejercicios).
If exist other path to determine this operation, i'm all eyes!!!
Thanks in advance.

Not sure if this is the only problem in your code, but what you're doing by setting
<ListBox.DataContext>
<InnovaCommerceHosteleryViewModels:frmEmpresasVM/>
</ListBox.DataContext>
for both list boxes is creating a separate instance of the ViewModel for each list box. Now I guess if you make any changes in the first list box' ViewModel instance, these changes will not be reflected in the second list box because this one binds to a totally different ViewModel instance.
Instead, try globally binding the ViewModel to the whole window / page / user control / etc. (depending on whether you;re doing WPF, Windows Phone, etc.), and let the list boxes inherit it to ensure that only one ViewModel instance is involved:
<Window.DataContext>
<InnovaCommerceHosteleryViewModels:frmEmpresasVM/>
</Window.DataContext>
EDIT:
Alternatively, you might as well instantiate the ViewModel once and store it as global resource:
<Window.Resources>
<InnovaCommerceHosteleryViewModels:frmEmpresasVM x:Key="Viewmodel" />
</Window.Resources>
and in the listboxes' DataContext just reference this global resouce:
<ListBox DataContext="{StaticResource Viewmodel}" ... />

ICollectionView's SourceCollection is null

I have a ViewModel with two ICollectionViews which are bound as ItemsSources to two different ListBoxes. Both wrap the same ObservableCollection, but with different filters. Everything works fine initially and both ListBoxes appear properly filled.
However when I change an item in the ObservableCollection and modify a property which is relevant for filtering, the ListBoxes don't get updated. In the debugger I found that SourceCollection for both ICollectionVIews is null although my ObservableCollection is still there.
This is how I modify an item making sure that the ICollectionViews are updated by removing and adding the same item:
private void UnassignTag(TagViewModel tag)
{
TrackChangedTagOnCollectionViews(tag, t => t.IsAssigned = false);
}
private void TrackChangedTagOnCollectionViews(TagViewModel tag, Action<TagViewModel> changeTagAction)
{
_tags.Remove(tag);
changeTagAction.Invoke(tag);
_tags.Add(tag);
}
The mechanism works in another context where I use the same class.
Also I realized that the problem disappears if I register listeners on the ICollectionViews' CollectionChanged events. I made sure that I create and modify them from the GUI thread and suspect that garbage collection is the problem, but currently I'm stuck... Ideas?
Update:
While debugging I realized that the SourceCollections are still there right before I call ShowDialog() on the WinForms Form in which my UserControl is hosted. When the dialog is shown they're gone.
I create the ICollectionViews like this:
AvailableTags = new CollectionViewSource { Source = _tags }.View;
AssignedTags = new CollectionViewSource { Source = _tags }.View;
Here's how I bind one of the two (the other one is pretty similar):
<ListBox Grid.Column="0" ItemsSource="{Binding AvailableTags}" Style="{StaticResource ListBoxStyle}">
<ListBox.ItemTemplate>
<DataTemplate>
<Border Style="{StaticResource ListBoxItemBorderStyle}">
<DockPanel>
<Button DockPanel.Dock="Right" ToolTip="Assign" Style="{StaticResource IconButtonStyle}"
Command="{Binding Path=DataContext.AssignSelectedTagCommand, RelativeSource={RelativeSource AncestorType={x:Type tags:TagsListView}}}"
CommandParameter="{Binding}">
<Image Source="..."/>
</Button>
<TextBlock Text="{Binding Name}" Style="{StaticResource TagNameTextBlockStyle}"/>
</DockPanel>
</Border>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
I use MvvmLight's RelayCommand<T> as ICommand implementation in my ViewModel:
AssignSelectedTagCommand = new RelayCommand<TagViewModel>(AssignTag);

I had this issue too, with a similar use-case. When I updated the underlying collection, I would call Refresh() on all the filtered views. Sometimes, this would result in a NullReferenceException thrown from within ListCollectionView.PrepareLocalArray() because SourceCollection is null.
The problem is that you shouldn't be binding to the CollectionView, but to the CollectionViewSource.View property.
Here's how I do it:
public class ViewModel {
// ...
public ViewModel(ObservableCollection<ItemViewModel> items)
{
_source = new CollectionViewSource()
{
Source = items,
IsLiveFilteringRequested = true,
LiveFilteringProperties = { "FilterProperty" }
};
_source.Filter += (src, args) =>
{
args.Accepted = ((ItemViewModel) args.Item).FilterProperty == FilterField;
};
}
// ...
public ICollectionView View
{
get { return _source.View; }
}
// ...
}

The reason for your issue is that the CollectionViewSource is getting garbage collected.

C# WPF Checkbox Databinding

I'm looking for the best way to populate a check boxes from the following code. I have looked into Binding but not really sure where to go.
Here is the edited code that is working
private void dpDateSelection_SelectedDateChanged(object sender, SelectionChangedEventArgs e)
{
DateTime? date = dpDateSelection.SelectedDate;
logDate = date != null ? date.Value.ToString("yyyy-MM-dd") : null;
dpDateSelection.ToolTip = logDate;
LoadLogs(logDate);
}
private void LoadLogs(string ldate)
{
string[] logs = Directory.GetFiles(logPath + ldate, "*.ininlog");
InitializeComponent();
logList = new ObservableCollection<String>();
logList.Clear();
foreach (string logName in logs)
{
string s = logName.Substring(logName.IndexOf(ldate) + ldate.Length + 1);
int extPos = s.LastIndexOf(".");
s = s.Substring(0, extPos);
logList.Add(s);
}
this.DataContext = this;
}
<ListBox x:Name="Logs" ItemsSource="{Binding logList}">
<ListBox.ItemTemplate>
<DataTemplate>
<CheckBox Content="{Binding}" ToolTip="{Binding}" Tag="{Binding}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

You will want to start by using an ItemsControl instead of a StackPanel, since ItemsControls are automatically set up to display collections of things:
<ItemsControl ItemsSource="{Binding Logs}"/>
Note the use of ItemsSource. With the accompanying binding string, it basically says "Look for a property on the DataContext called "Logs" and put everything in it into this control".
Next you said you wanted this displayed as checkboxes, so we use an item template:
<ItemsControl ItemsSource="{Binding Logs}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Content={Binding .}/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
This says "Use a checkbox for each Item in the ItemsSource". The DataTemplate can be a Grid or other collection control as well, so this is a really powerful feature in WPF. The "Binding ." just binds to the object itself (a string in this case, so we don't need a special path).
Finally, you need to set up a property to bind to in your view model:
ObservableCollection<String> Logs {get; set;}
You want an ObservableCollection so that when anything is added to or removed from the list, it automatically updates the UI. If you are going to be completely replacing the list (assignment), then you need to implement INotifyPropertyChanged and invoke the PropertyChanged event in that properties setter.
In your posted loop, you would add each log file to this property.
Also, make sure that somewhere you set the DataContext property of the XAML file (View) to your view model object. If everything is in code behind, use DataContext = this. Note that doing this is considered bad practice, and you should use a separate class (ViewModel).
You didn't mention what you wanted the CheckBoxes to do, so I haven't included anything related to that in my answer. You will likely want to abstract your logs into an object with a "Selected" property you can then bind the IsChecked property of the CheckBoxes to.
Obviously this is a lot to take in, please let me know if I can clarify anything or help further!
Update
You put the property in your ViewModel (DataContext). Whatever class that is, you write:
ObservableCollection<String> Logs {get; set;}
private void LoadLogs()
{
string[] logs = Directory.GetFiles(logPath + logDate, "*.ininlog");
foreach(string logName in logs)
{
string s = logName.Substring(logName.IndexOf(logDate) + logDate.Length + 1);
int extPos = s.LastIndexOf(".");
s = s.Substring(0, extPos);
//MessageBox.Show(s);
Logs.Add(s); //Add the parsed file name to the list
}
}