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Where/how is the "NotifyPropertyChanged" defined? I do every thing in a Window class and there is that method not defined 
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To bind to a property in your codebehind/viewmodel you need to implement this Interface. Here[^] is the MSDN page for this interface.
Hope this helps
Live for today. Plan for tomorrow. Party tonight!
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using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel;
using System.IO;
namespace SwitchLanguage
{
public partial class MainWindow : Window, INotifyPropertyChanged
{
string folderPath = @"C:\Users\SwitchLanguage\";
ObservableCollection<LanguageItem> words;
public event PropertyChangedEventHandler PropertyChanged;
public MainWindow()
{
InitializeComponent();
PropertyChanged += new PropertyChangedEventHandler(MainWindow_PropertyChanged);
}
private void btnUK_Click(object sender, RoutedEventArgs e)
{
ReadFile("UK.txt");
}
private void btnUS_Click(object sender, RoutedEventArgs e)
{
ReadFile("US.txt");
}
private void ReadFile(string file)
{
if (!File.Exists(folderPath + file))
{
throw new FileNotFoundException("Language file doesn't exist");
}
StreamReader sr = new StreamReader(folderPath + file);
ObservableCollection<LanguageItem> words = new ObservableCollection<LanguageItem>();
while (!sr.EndOfStream)
{
string[] parts = sr.ReadLine().Split('=');
LanguageItem languageItem = new LanguageItem();
languageItem.ID = int.Parse(parts[0]);
languageItem.Word = parts[1];
words.Add(languageItem);
}
Words = words;
sr.Close();
}
public ObservableCollection<LanguageItem> Words
{
get { return words; }
set
{
if (words != value)
{
words = value;
PropertyChanged(this, new PropertyChangedEventArgs("Words"));
}
}
}
void MainWindow_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
Console.WriteLine("");
}
}
public class LanguageItem
{
public int ID { get; set; }
public string Word { get; set; }
}
}
<Window x:Class="SwitchLanguage.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>
<Label Name="lblWord" Content="{Binding Path=Words[0].Word}" Margin="50,-100,0,0" Width="200" Height="30"></Label>
<Button Width="100" Height="40" Click="btnUK_Click" Content="UK" Margin="-100,0,0,0"></Button>
<Button Width="100" Height="40" Click="btnUS_Click" Content="US" Margin="100,0,0,0"></Button>
</Grid>
</Window>
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Well, the most obvious thing here is that you haven't set the DataContext of your window to the Window class. To be honest, what you have here is not the way I would have chosen to do it, but if it eventually works for you...
Anyway all you need to do is, after the call to InitializeComponent, add
DataContext = this;
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Thanks! That did the trick 
Pete, would you have solve this?
I don't like to use index assigners in the XAML code Words[0].Word, but I don't see any other solution.
In my case I cannot use resource files. Resource file (what I have seen) must be compiled into the application. To use a text file is much easier since I can get as many languages I want if all files follow the correct format.
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We use a database to store the text, and this is bound in at runtime. It's that straightforward.
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Hi Pete,
Just a quick question on this topic. You said that you store you dictionaries in a database, and I can see the value in this, but you also said you bind the values at runtime. Does this mean that you have a property for each and every label, group box header, tab header etc that needs to be localised, and then bind to the property, or do you store your localising (is that a word?) strings in some sort of collection? If it is the former, then this must be a hell of a job, as on some forms, you could have up to 20 - 25 labels etc that need to be localised, and so would need to declare that many properties in your vewmodel, and if it is the latter, how do you bind the labels etc to the collection ? The way I proposed to the OP, i.e using the indexers, I got from one of Sasha Barbers articles WPF:Binding to individual collection items[^], and would appreciate it if you could give me your thought on this, as it does seem a bit of a hack, and could potentially lead to disastrous results if your dictionaries are not in sync.
Thanks for your time.
Wayne.
Live for today. Plan for tomorrow. Party tonight!
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We use a custom localisable MarkupExtension to handle this. The beauty of storing the values in the database is that, with a simple query, we can find any items that haven't been localised without needing to run up the application.
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Tish - that's the sound of a light bulb switching on in my head. You certainly know your stuff! Many thanks.
Live for today. Plan for tomorrow. Party tonight!
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No problem. Glad to help.
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Pete O'Hanlon wrote: We use a custom localisable MarkupExtension to handle this
And here I was going to ask for an example of the binding syntax!
Never underestimate the power of human stupidity
RAH
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This is how I would do it (only if my requirements stated I had to use your language files - otherwise I would use Resource Files as Abhinav suggestes)
Your LanguageItem class:
class LanguageItem
{
public int ID { get; set; }
public string Word { get; set; }
}
A separate class which I will call LanguageViewModel:
class LanguageViewModel : INotifyPropertyChanged
{
enum LanguageChoice
{
UK,
US
}
private LanguageChoice selectedLanguage = LanguageChoice.UK;
private string languageText = "Switch to US English";
public string LanguageText
{
get
{
return languageText;
}
set
{
if (languageText != value)
{
languageText = value;
NotifyPropertyChanged("LanguageText");
}
}
}
ObservableCollection<LanguageItem> words = new ObservableCollection<LanguageItem>();
public ObservableCollection<LanguageItem> Words
{
get
{
return words;
}
set
{
if (words != value)
{
words = value;
NotifyPropertyChanged("Words");
}
}
}
public LanguageViewModel()
{
LoadLanguage(selectedLanguage);
}
private RelayCommand switchCommand;
public ICommand SwitchCommand
{
get
{
return switchCommand ?? (switchCommand = new RelayCommand(() => ObeySwitchCommand()));
}
}
private void ObeySwitchCommand()
{
selectedLanguage = selectedLanguage == LanguageChoice.UK ? LanguageChoice.US : LanguageChoice.UK;
LanguageText = selectedLanguage == LanguageChoice.UK ? "Switch to US English" : "Switch to UK English";
LoadLanguage(selectedLanguage);
}
void LoadLanguage(LanguageChoice languageToLoad)
{
string path;
if (languageToLoad == LanguageChoice.UK)
{
path = @"C:\Users\SwitchLanguage\UK.txt";
}
else
{
path = @"C:\Users\SwitchLanguage\US.txt";
}
StreamReader sr = new StreamReader(path);
ObservableCollection<LanguageItem> newWords = new ObservableCollection<LanguageItem>();
while (!sr.EndOfStream)
{
string[] parts = sr.ReadLine().Split(new char[] { ',' });
int index;
int.TryParse(parts[0], out index);
LanguageItem li = new LanguageItem() { ID = index, Word = parts[1] };
newWords.Add(li);
}
Words = newWords;
}
#region INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(String info)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(info));
}
}
#endregion
}
My XAML File (Note no code in code behind):
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Label Content="{Binding Path=Words[0].Word}"/>
<Label Content="{Binding Path=Words[1].Word}" Grid.Column="1"/>
<Button Grid.Row="1" Grid.Column="1" HorizontalAlignment="Right" VerticalAlignment="Bottom"
Command="{Binding Path=SwitchCommand}" Content="{Binding Path=LanguageText}"
Width="100" Height="23"/>
Then I would override the OnStartUp method in the App.xaml.cs file like this:
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
LanguageViewModel vm = new LanguageViewModel();
LanguageTest lt = new LanguageTest();
lt.DataContext = vm;
lt.ShowDialog();
}
And here is a bog standard RelayCommand class that is used for binding the Button's click command to the SwitchCommand on the ViewModel:
public class RelayCommand : ICommand
{
readonly Action execute;
readonly Func<bool> canExecute;
public RelayCommand(Action execute)
: this(execute, null)
{
}
public RelayCommand(Action execute, Func<bool> canExecute)
{
if (execute == null)
throw new ArgumentNullException("execute");
this.execute = execute;
this.canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return canExecute == null ? true : canExecute();
}
public event EventHandler CanExecuteChanged
{
add
{
if (canExecute != null)
CommandManager.RequerySuggested += value;
}
remove
{
if (canExecute != null)
CommandManager.RequerySuggested -= value;
}
}
public void Execute(object parameter)
{
execute();
}
}
Live for today. Plan for tomorrow. Party tonight!
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I would look at using a resource file for maintaining different languages.
See WPF Localization Using RESX Files[^] for an example.
Too much of heaven can bring you underground
Heaven can always turn around
Too much of heaven, our life is all hell bound
Heaven, the kill that makes no sound
modified on Thursday, September 1, 2011 7:23 AM
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With WCF you can retrieve data, etc into silverlight UI using asyncronous calls...
Then is there any reason for backgrooundworker process to be used in silverlight?
Thanks
modified on Thursday, September 1, 2011 1:28 AM
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Define required! I am yet to use a BGW process in SL.
Never underestimate the power of human stupidity
RAH
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Hello,
I updated the question.
Thanks
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I'm sure you've asked this question before. Yes, you can use a background worker to do something in Silverlight, but in most cases it's not necessary because of the asynchronous nature of the client/server roundtrip. Saying that, you could be attempting to do something entirely on the client side, e.g. performing a long running calculation, and you should use some form of threading for this.
The answer you are looking for:
Roundtrip = asynchronous = no need for additional threading
Client side only = synchronous = you might want to use threading here.
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In that case, on the client side, to use threading, I can use background worker? and not manually creating threads like thread t = new thread(...)?
Thanks
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arkiboys wrote: on the client side, to use threading, I can use background worker
Yes.
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I see.
So in silverlight, I do not need to learn how to do manual threading as long as I know backgroundworker process?
Thanks
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That's correct. Learning manual threading is good knowledge to have, it will make you a better coder, but it isn't absolutely necessary.
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I see.
This is now clear.
Thanks
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To be able to develop in windows phone, as well as having the visual studio express 2010, should I also install the VS.NET 2010 Express for Windows Phone
Thanks
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Hi!
Please help me to solve the problem:
I got DataSet, which contains 2 DataTables:
Categories (CategoryID, CategoryName)
Products(ProductID, CategoryID, Name)
These tables are linked using DataRelation by CategoryID key.
So, each product has category.
I got TreeView bound to DataSet.Tables["Categories"] - no problem here. Category names are displayed correctly as tree view items(having DisplayMemberPath=CategoryName)
And I got ListView.
So, I need to show Products in this ListView, that contains only the products of category selected in TreeView.
I don't know how to bind. Could you please help me?
Thanks!
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Personally, I think you are going about things the wrong way. When it comes to WPF, as I told you before, using datasets and trying to bind to them is seriously a PITA. For a start, I would create 2 classes, one for Products and one for Categories. These can be really basic. The Category class should have a property that returns a List of Products. Then I would have another class (call it a viewmodel if you will) that would implement the INotifyPropertyChanged[^] Interface. This viewmodel need only have 2 properties, one which returns an ObservableCollection of Categories, call it Categories(to be original), and another that returns a specific Category (call it SelectedCategory). These properties should call your NotifyPropertyChanged event handler whenever they are changed. The viewmodel should also be able to populate the collection of categories, either from a database or some other source, or it could be populated in the constructor. Then in your Window/UserControl constructor, all you need to do is create an instance of the viewmodel class, and set the Window/UserControl's datacontext to the instance (this can be done in the constructor). In your XAML, you set up 2 ListViews. The first ListView should have it's ItemsSource property set to bind to the Categories property of the view model. The second ListView, the one with 2 columns for each property of the product, should have it's ItemsSource bound to the SelectedCategory's Products Property, with the first column bound to the product Id, and the second Column bound to the Name. And that's it, Simples.
Doing things this way, will make your life so easier. If you have any problems with implementing this, I will try and help if I can.
Live for today. Plan for tomorrow. Party tonight!
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