Im trying to implement the MVVM Pattern i just want to have a TextBox that shows some initial text at startup.
this is my view: (dont care about the buttons and the listbox for now)
<Window x:Class="Friends.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">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBox Grid.Row="0" Width="150" Text="{Binding Friend}"></TextBox>
<ListBox Grid.Row="1" Width="150"></ListBox>
<Button Grid.Row="2" Content="Previous" Width="150"></Button>
<Button Grid.Row="3" Content="Next" Width="150"></Button>
</Grid>
this is my model:
public class FriendsModel : INotifyPropertyChanged
{
private string _firstName;
public string FirstName
{
get { return _firstName; }
set
{
_firstName = value;
RaisePropertyChanged("FirstName");
}
}
public FriendsModel(string _initialName)
{
_firstName = _initialName;
}
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string _newName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) {
handler(this, new PropertyChangedEventArgs(_newName));
}
}
}
and this is my viewmodel:
public class FriendsViewModel
{
public FriendsModel Friend { get; set; }
public FriendsViewModel()
{
Friend = new FriendsModel("Paul");
}
}
in the code behind i have:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new FriendsViewModel();
}
}
my project is building without any errors but it doesnt show the text in my textbox. Can anyone help me?
thanks in advance
edit:
i changed it to
<TextBox Grid.Row="0" Width="150" Text="{Binding Friend.Firstname}"></TextBox>
its still not working.
The binding should point the FirstName property. WPF can not figure out by him self how to convert Friend class to string.
Text="{Binding Friend.FirstName}"
the Friend in the binding represents the full object, you must specify the membre...
try to replace{Binding Friend} by {Binding Friend.FirstName}
The DataContext is being set right after InitializeComponent() is called, this means that the bindings have already been setup, the textbox is correctly binding to the FirstName property but at the point of binding it's empty.
if you want the textbox to update when the property does you'll need to set DataContext before InitializeComponent()
public MainWindow()
{
DataContext = new FriendsViewModel();
InitializeComponent();
}
gives the result
Have you tried this:
public FriendsModel(string _initialName)
{
this.FirstName = _initialName;
}
Regards,
Related
I'm newbie on WPF and I have text box and button which open folder browser dialog.
When the user select folder I would like text box will contain the selected path.
So on MainWindow I added two variables:
public partial class MainWindow : Window
{
public string outputFolderPath { get; set; }
string reducedModelFolderPath { get; set; }
}
and when user selected folder path (after open folder dialog) I updated those variables by doing (for example):
outputFolderPath = dialog.SelectedPath
In MainWindow.xaml:
<TextBox x:Name="outputFolder" Width ="200" Height="30" Grid.Row="1" Grid.Column="1" Margin="5 10">
How can I bind TextBox.Text to outputFolderPath variable?
Thanks for your assitance!
You need to set DataContext of your window to this, to access your property in XAML, and after that bind to the property. As you are binding not to DependencyProperty, you should notify your binding that property has changed, which could be done by implementing INotifyPropertyChanged interface in your Window.
I've provided sample code to show the concept.
But this is very ugly, much better to use MVVM pattern instead.
MainWindow.xaml.cs
public partial class MainWindow : Window, INotifyPropertyChanged
{
public string outputFolderPath { get; set; }
public MainWindow()
{
InitializeComponent();
DataContext = this;
}
public event PropertyChangedEventHandler PropertyChanged;
private void Button_Click(object sender, RoutedEventArgs e)
{
outputFolderPath = "Some data";
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(outputFolderPath)));
}
}
MainWindow.xaml
<Window x:Class="simplest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:simplest"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Button Click="Button_Click" Content="Go" />
<TextBox x:Name="outputFolder" Width ="200" Height="30" Grid.Row="1" Grid.Column="1" Margin="5 10" Text="{Binding outputFolderPath}"/>
</Grid>
</Window>
I am developing a small application for learning purpose. I find that when I bind ItemControl's ItemSource to a ViewModel property in XAML, it doesn't work in an expected way. i.e. It loads the underlying collection with values at the loading time, but any changes to it are not reflected.
However, if I set Itemsource in Codebehind, it works.
When the form is loaded, it shows 2 note objects. Clicking on button should show the 3rd one. I don't understand why setting DataContext using XAML doesn't update to changes in collection. I am sharing snippet of the code here. Any help greatly appreciated.
Cut-down version of XAML -
<Window x:Class="NotesApp.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:NotesApp"
xmlns:vm="clr-namespace:NotesApp.ViewModel"
Title="MainWindow" Height="480" Width="640">
<Window.DataContext >
<vm:MainViewModel/>
</Window.DataContext>
<DockPanel >
<ScrollViewer VerticalScrollBarVisibility="Auto">
<ItemsControl Name="NoteItemControl" ItemsSource="{Binding notes}" Background="Beige" >
<ItemsControl.LayoutTransform>
<ScaleTransform ScaleX="{Binding Value, ElementName=zoomSlider}" ScaleY="{Binding Value, ElementName=zoomSlider}" />
</ItemsControl.LayoutTransform>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Name="NoteBorder" Background="Green" CornerRadius="3" Margin="5,3,5,3">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<TextBlock Text="{Binding noteText}" Margin="5,3,5,3"/>
<StackPanel Grid.Row="1" Orientation="Vertical" >
<Line X1="0" Y1="0" X2="{Binding ActualWidth,ElementName=NoteBorder}" Y2="0" Stroke="Black" StrokeThickness="1"/>
<TextBlock Text="{Binding Category}" Margin="5,3,5,3"/>
</StackPanel>
</Grid>
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>
</DockPanel>
</Window>
View Code behind-
namespace NotesApp
{
public partial class MainWindow : Window
{
MainViewModel ViewModel { get; set; }
public MainWindow()
{
InitializeComponent();
ViewModel = new MainViewModel();
// IT WORKS IF I BRING IN THIS STATEMENT
//NoteItemControl.ItemsSource = ViewModel.notes;
}
private void Button_Click_1(object sender, RoutedEventArgs e)
{
ViewModel.AddNote(new Note("note3", "Category 3"));
}
}
}
ViewModel -
namespace NotesApp.ViewModel
{
public class MainViewModel: INotifyPropertyChanged
{
ObservableCollection<Note> _notes;
public ObservableCollection<Note> notes
{
get
{ return _notes; }
set
{
_notes = value;
OnPropertyChanged("notes");
}
}
public void AddNote(Note note)
{
_notes.Add(note);
OnPropertyChanged("notes");
}
public MainViewModel ()
{
notes = new ObservableCollection<Note>();
notes.Add(new Note("note1", "Category 1"));
notes.Add(new Note("note2", "Category 2"));
}
public event PropertyChangedEventHandler PropertyChanged = delegate { };
protected virtual void OnPropertyChanged(string propertyName = null)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs( propertyName));
}
}
}
You create a MainViewModel instance and assign it to the MainWindow's DataContext in XAML
<Window.DataContext >
<vm:MainViewModel/>
</Window.DataContext>
The bindings in your XAML use this instance as their source object, as long as you do not explicitly specify some other source. So there is no need (and it's an error) to create another instance in code behind.
Change the MainWindow's constructor like this:
public MainWindow()
{
InitializeComponent();
ViewModel = (MainViewModel)DataContext;
}
Try this :
<Window.Resources>
<vm:MainViewModel x:Key="mainVM"/>
</Window.Resources>
Now use this key as a static resource wherever you bind something like :
<ItemsControl Name="NoteItemControl" ItemsSource="{Binding notes,Source={StaticResource mainVM},Mode=TwoWay}" Background="Beige" >
If you do this, you dont need any datacontext
I have a text box, which default value I want to bind to Combo box selecteItem, and same time I want my text box to be binded to Mvvm object property?
I checked here but the multibinding confuse me.
I would prefer to have xaml solution for this issue.
Addition:
In combobox I will select an Account, that account contain some values (Amount), I want to display Amount, But need my text box to be bounded to mvvm model object element stAmount. so the user can change the amount selected by combobbox and then this modified or unchanged amount value could be stored to text box binded model-object element (stAmount)
Making use of INotifyPropertyChanged:
XAML
<Window x:Class="INotifyPropertyChangedExample.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
Title="INotifyPropertyChanged Example" Width="380" Height="100">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="150" />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Label Content="Account Name:" />
<Label Grid.Row="1" Grid.Column="0" Content="Account Balance:" />
<ComboBox Grid.Row="0" Grid.Column="1" Width="200" Height="25" ItemsSource="{Binding AccountsCollection}" SelectedItem="{Binding SelectedAccount}" DisplayMemberPath="Name" />
<TextBox Grid.Column="1" Grid.Row="1" Width="200" Height="25" Text="{Binding SelectedAccount.Balance}" />
</Grid>
</Window>
C#
namespace INotifyPropertyChangedExample
{
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows;
public partial class MainWindow : Window, INotifyPropertyChanged
{
private ObservableCollection<Account> acctountsCollection;
public ObservableCollection<Account> AccountsCollection
{
get
{
return this.acctountsCollection;
}
set
{
this.acctountsCollection = value;
OnPropertyChanged();
}
}
private Account selectedAccount;
public Account SelectedAccount
{
get
{
return this.selectedAccount;
}
set
{
this.selectedAccount = value;
OnPropertyChanged();
}
}
public MainWindow()
{
InitializeComponent();
this.AccountsCollection = new ObservableCollection<Account>()
{
new Account { Id = 1, Name = "My super account", Balance = 123.45 },
new Account { Id = 2, Name = "My super account 2", Balance = 543.21 },
};
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
public class Account
{
public int Id { get; set; }
public string Name { get; set; }
public double Balance { get; set; }
}
}
In this example we bind an ObservableCollection of Account objects to your ComboBox and keep track of which Account is selected through the SelectedItem property. We bind the TextBox text property to the Balance property of the selected Account object. Therefore when then selected Account object changes the value displayed in the TextBox changes to reflect the Balance of the Account.
Additionally if you change the value in the TextBox, the Balance value of the Account object is updated.
It seems to me like you want bind your textbox to the selected value property in your viewmodel not the combo box.
using System.Collections.ObjectModel;
using System.Windows;
namespace WpfApplication1
{
public partial class MainWindow : Window
{
public ObservableCollection<string> Items
{
get { return (ObservableCollection<string>)GetValue(ItemsProperty); }
set { SetValue(ItemsProperty, value); }
}
public static readonly DependencyProperty ItemsProperty =
DependencyProperty.Register("Items", typeof(ObservableCollection<string>), typeof(MainWindow), new PropertyMetadata(null));
public string SelectedValue
{
get { return (string)GetValue(SelectedValueProperty); }
set { SetValue(SelectedValueProperty, value); }
}
public static readonly DependencyProperty SelectedValueProperty =
DependencyProperty.Register("SelectedValue", typeof(string), typeof(MainWindow), new PropertyMetadata(null));
public MainWindow()
{
InitializeComponent();
Items = new ObservableCollection<string>();
Items.Add("Value 1");
Items.Add("Value 2");
Items.Add("Value 3");
Items.Add("Value 4");
Items.Add("Value 5");
Items.Add("Value 6");
}
}
}
and the xaml
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
Title="MainWindow" Height="350" Width="525">
<Grid >
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<ComboBox Grid.Row="0" ItemsSource="{Binding Items}" SelectedItem="{Binding SelectedValue}"/>
<TextBox Grid.Row="1" Text="{Binding SelectedValue}"/>
</Grid>
</Window>
I wrote a customcontrol. It is a textbox with a button which opens a OpenFileDialog.
The Text property of the TextBox is bound to my dependency property "FileName". And if the user selects a file via the OpenFileDialog, i set the result to this property.
The TextBox gets the right value through binding.
But now my problem. For my view I'm using a ViewModel. So I have a Binding to my DependencyProperty "FileName" to the property in my ViewModel.
After changing the "FileName" property (changes direct to the textbox or selecting a file via the dialog), the viewmodel property doesn't update.
CustomControl.xaml.cs
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using Microsoft.Win32;
namespace WpfApplication1.CustomControl
{
/// <summary>
/// Interaction logic for FileSelectorTextBox.xaml
/// </summary>
public partial class FileSelectorTextBox
: UserControl, INotifyPropertyChanged
{
public FileSelectorTextBox()
{
InitializeComponent();
DataContext = this;
}
#region FileName dependency property
public static readonly DependencyProperty FileNameProperty = DependencyProperty.Register(
"FileName",
typeof(string),
typeof(FileSelectorTextBox),
new FrameworkPropertyMetadata(string.Empty,
FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
new PropertyChangedCallback(OnFileNamePropertyChanged),
new CoerceValueCallback(OnCoerceFileNameProperty)));
public string FileName
{
get { return (string)GetValue(FileNameProperty); }
set { /*SetValue(FileNameProperty, value);*/ CoerceFileName(value); }
}
private bool _shouldCoerceFileName;
private string _coercedFileName;
private object _lastBaseValueFromCoercionCallback;
private object _lastOldValueFromPropertyChangedCallback;
private object _lastNewValueFromPropertyChangedCallback;
private object _fileNameLocalValue;
private ValueSource _fileNameValueSource;
private static void OnFileNamePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (d is FileSelectorTextBox)
{
(d as FileSelectorTextBox).OnFileNamePropertyChanged(e);
}
}
private void OnFileNamePropertyChanged(DependencyPropertyChangedEventArgs e)
{
LastNewValueFromPropertyChangedCallback = e.NewValue;
LastOldValueFromPropertyChangedCallback = e.OldValue;
FileNameValueSource = DependencyPropertyHelper.GetValueSource(this, FileNameProperty);
FileNameLocalValue = this.ReadLocalValue(FileNameProperty);
}
private static object OnCoerceFileNameProperty(DependencyObject d, object baseValue)
{
if (d is FileSelectorTextBox)
{
return (d as FileSelectorTextBox).OnCoerceFileNameProperty(baseValue);
}
else
{
return baseValue;
}
}
private object OnCoerceFileNameProperty(object baseValue)
{
LastBaseValueFromCoercionCallback = baseValue;
return _shouldCoerceFileName ? _coercedFileName : baseValue;
}
internal void CoerceFileName(string fileName)
{
_shouldCoerceFileName = true;
_coercedFileName = fileName;
CoerceValue(FileNameProperty);
_shouldCoerceFileName = false;
}
#endregion FileName dependency property
#region Public Properties
public ValueSource FileNameValueSource
{
get { return _fileNameValueSource; }
private set
{
_fileNameValueSource = value;
OnPropertyChanged("FileNameValueSource");
}
}
public object FileNameLocalValue
{
get { return _fileNameLocalValue; }
set
{
_fileNameLocalValue = value;
OnPropertyChanged("FileNameLocalValue");
}
}
public object LastBaseValueFromCoercionCallback
{
get { return _lastBaseValueFromCoercionCallback; }
set
{
_lastBaseValueFromCoercionCallback = value;
OnPropertyChanged("LastBaseValueFromCoercionCallback");
}
}
public object LastNewValueFromPropertyChangedCallback
{
get { return _lastNewValueFromPropertyChangedCallback; }
set
{
_lastNewValueFromPropertyChangedCallback = value;
OnPropertyChanged("LastNewValueFromPropertyChangedCallback");
}
}
public object LastOldValueFromPropertyChangedCallback
{
get { return _lastOldValueFromPropertyChangedCallback; }
set
{
_lastOldValueFromPropertyChangedCallback = value;
OnPropertyChanged("LastOldValueFromPropertyChangedCallback");
}
}
#endregion FileName dependency property
private void btnBrowse_Click(object sender, RoutedEventArgs e)
{
FileDialog dlg = null;
dlg = new OpenFileDialog();
bool? result = dlg.ShowDialog();
if (result == true)
{
FileName = dlg.FileName;
}
txtFileName.Focus();
}
#region INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion INotifyPropertyChanged
}
}
CustomControl.xaml
<UserControl x:Class="WpfApplication1.CustomControl.FileSelectorTextBox"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="23" d:DesignWidth="300">
<Border BorderBrush="#FF919191"
BorderThickness="0">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" MinWidth="80" />
<ColumnDefinition Width="30" />
</Grid.ColumnDefinitions>
<TextBox Name="txtFileName"
HorizontalAlignment="Stretch"
VerticalAlignment="Center"
Grid.Column="0"
Text="{Binding FileName}" />
<Button Name="btnBrowse"
Click="btnBrowse_Click"
HorizontalContentAlignment="Center"
ToolTip="Datei auswählen"
Margin="1,0,0,0"
Width="29"
Padding="1"
Grid.Column="1">
<Image Source="../Resources/viewmag.png"
Width="15"
Height="15" />
</Button>
</Grid>
</Border>
</UserControl>
Using in a view:
<Window x:Class="WpfApplication1.MainView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:WpfApplication1.ViewModels"
xmlns:controls="clr-namespace:WpfApplication1.CustomControl"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<vm:MainViewModel />
</Window.DataContext>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="10" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<DataGrid ItemsSource="{Binding Files}" AutoGenerateColumns="False">
<DataGrid.Columns>
<DataGridTemplateColumn Header="File name" Width="*">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<controls:FileSelectorTextBox FileName="{Binding .}" Height="30" />
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>
<ListBox ItemsSource="{Binding Files}" Grid.Row="2">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Window>
And the ViewModel:
using System.Collections.ObjectModel;
using System.ComponentModel;
namespace WpfApplication1.ViewModels
{
internal class MainViewModel
: INotifyPropertyChanged
{
public MainViewModel()
{
Files = new ObservableCollection<string> { "test1.txt", "test2.txt", "test3.txt", "test4.txt" };
}
#region Properties
private ObservableCollection<string> _files;
public ObservableCollection<string> Files
{
get { return _files; }
set
{
_files = value;
OnPropertyChanged("Files");
}
}
#endregion Properties
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion INotifyPropertyChanged Members
}
}
Is there any wrong using of the dependency property?
Note: The problem only occurs in DataGrid.
You need to set binding Mode to TwoWay, because by default binding works one way, i.e. loading changes from the view model, but not updating it back.
<controls:FileSelectorTextBox FileName="{Binding FileName, Mode=TwoWay}" Height="30" />
Another option is to declare your custom dependency property with BindsTwoWayByDefault flag, like this:
public static readonly DependencyProperty FileNameProperty =
DependencyProperty.Register("FileName",
typeof(string),
typeof(FileSelectorTextBox),
new FrameworkPropertyMetadata(default(string), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
Also when you change your custom dependency property from inside your control use SetCurrentValue method instead of directly assigning the value using property setter. Because if you assign it directly you will break the binding.
So, instead of:
FileName = dlg.FileName;
Do like this:
SetCurrentValue(FileNameProperty, dlg.FileName);
Change as following:
<TextBox Name="txtFileName"
HorizontalAlignment="Stretch"
VerticalAlignment="Center"
Grid.Column="0"
Text="{Binding FileName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
The code below is supposed to show a stack of three list boxes, each containing a list of all the system fonts. The first is unsorted, and the second and third are alphabetized. But the third one is empty. I don't see any binding error messages in the VS Output window when debugging.
The markup is:
<Window x:Class="FontList.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:FontList"
Title="MainWindow" Height="600" Width="400">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<ListBox Grid.Row="0" ItemsSource="{Binding Source={x:Static Fonts.SystemFontFamilies}}" />
<ListBox Grid.Row="1" ItemsSource="{Binding Path=SystemFonts}" />
<ListBox Grid.Row="2" ItemsSource="{Binding Source={x:Static local:MainWindow.SystemFonts}}" />
</Grid>
The code behind is:
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Media;
namespace FontList
{
public partial class MainWindow : Window
{
public static List<FontFamily> SystemFonts { get; set; }
public MainWindow() {
InitializeComponent();
DataContext = this;
SystemFonts = Fonts.SystemFontFamilies.OrderBy(f => f.ToString()).ToList();
}
}
}
What's wrong with the third binding?
You need to initialize SystemFonts before you call InitalizeComponent. The WPF binding has no way of knowing the property's value changed.
public MainWindow() {
SystemFonts = Fonts.SystemFontFamilies.OrderBy(f => f.ToString()).ToList();
InitializeComponent();
DataContext = this;
}
or better yet, use:
static MainWindow() {
SystemFonts = Fonts.SystemFontFamilies.OrderBy(f => f.ToString()).ToList();
}
public MainWindow() {
InitializeComponent();
DataContext = this;
}
The Bindings are created during InitializeComponent, while SystemFonts is null. After you set it, the binding has no way of knowing that the property's value has changed.
You can also set SystemFonts in a static constructor, which is probably preferable since it's a static property. Otherwise every instantiation of MainWindow will change the static property.
public partial class MainWindow : Window {
public static List<FontFamily> SystemFonts{get; set;}
static MainWindow {
SystemFonts = Fonts.SystemFontFamilies.OrderBy(f => f.ToString()).ToList();
}
...
}