Develop Reference

INotifyPropertyChanged in wpf application of List

Problem
I want to refresh my wpf view when a change is made in a List of objects in my application, but it wont register the INotifyChanged method when I change a value.
What I've tried
I went to multiple different stackoverflow pages with sort of the same problem but I don't get it working right. It wont register a change in a object in the list.
my code
below is the code for the MainWindow of the WPF application in wher with the last button click I change the value of XLocation in an object out of a list.
public partial class MainWindow : Window
{
private string filePathArtist { get; set; }
private string filePathGrid { get; set; }
public Game.Game Game { get; set; }
public MainWindow()
{
InitializeComponent();
filePathGrid = String.Empty;
filePathArtist = String.Empty;
}
private void BtnOpen_Click(object sender, RoutedEventArgs e)
{
OpenFileDialog openFileDialog = new OpenFileDialog();
bool? res = openFileDialog.ShowDialog();
if (res == true)
{
string filepathgrid = openFileDialog.FileName;
filePathGrid = filepathgrid;
GridTextBox.Text = filepathgrid;
}
}
private void PickArtistBtn_Click(object sender, RoutedEventArgs e)
{
OpenFileDialog openFileDialog = new OpenFileDialog();
bool? res = openFileDialog.ShowDialog();
if (res == true)
{
string filepathartist = openFileDialog.FileName;
filePathArtist = filepathartist;
ArtistTextBox.Text = filepathartist;
}
}
private void CreateGridBtn_Click(object sender, RoutedEventArgs e)
{
Game = new Game.Game(filePathGrid, filePathArtist);
this.DataContext = Game;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
Game.Artists[0].XLocation = 30;
}
}
Next code is the Game class where is implemented a INotfyPropertyChanged on the list of Artists.
public class Game : INotifyPropertyChanged
{
public List<Artist> _artists;
public List<Artist> Artists
{
get
{
return _artists;
}
set
{
_artists = value;
OnPropertyChanged("Artists");
}
}
public List<ITile> Tiles { get; set; }
public Game()
{
}
public Game(string graphPath, string artistPath)
{
IDataParser graphParser = DataFactory.DataFactory.Instance.CreateParser(graphPath);
IDataParser artistParser = DataFactory.DataFactory.Instance.CreateParser(artistPath);
Tiles = graphParser.ParseGridData(graphPath);
Artists = artistParser.ParseArtistData(artistPath);
Test = "new Game";
}
public string Test { get; set; } = "t";
public event PropertyChangedEventHandler? PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Ive also added the INotifyPropertyChanged in the Artists class
public class Artist : INotifyPropertyChanged
{
private float _xLocation;
private float _yLocation;
private int _xVelocity;
private int _yVelocity;
public float XLocation
{
get => _xLocation;
set
{
_xLocation = value;
OnPropertyChanged("XLocation");
}
}
public float ConvertedXLoc
{
get => XLocation * (float)3.75;
set { }
}
public float YLocation
{
get => _yLocation;
set
{
_yLocation = value;
OnPropertyChanged("YLocation");
}
}
public float ConvertedYLoc
{
get => YLocation * (float)3.75;
set { }
}
public int XVelocity
{
get => _xVelocity;
set
{
_xVelocity = value;
}
}
public int YVelocity
{
get => _yVelocity;
set
{
_yVelocity = value;
}
}
public event PropertyChangedEventHandler? PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Then here is the Xaml code where I bind the objects to the wpf UI.
<Window x:Class="BroadwayBoogie.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:game="clr-namespace:BroadwayBoogie.Game"
mc:Ignorable="d"
Title="MainWindow" Height="900" Width="900"
>
<Window.DataContext>
<game:Game/>
</Window.DataContext>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="201*"/>
<ColumnDefinition Width="199*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="21*"/>
<RowDefinition Height="401*"/>
<RowDefinition Height="20*"/>
</Grid.RowDefinitions>
<Button x:Name="BtnOpen" Content="Pick Grid" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top" Click="BtnOpen_Click"/>
<TextBox x:Name="GridTextBox" HorizontalAlignment="Center" TextWrapping="NoWrap" VerticalAlignment="Center" Width="266" />
<Button x:Name="PickArtistBtn" Content="Pick Artist" HorizontalAlignment="Left" Margin="356,0,0,0" VerticalAlignment="Center" Click="PickArtistBtn_Click" RenderTransformOrigin="-0.135,0.647"/>
<TextBox x:Name="ArtistTextBox" HorizontalAlignment="Left" Margin="30,14,0,0" TextWrapping="NoWrap" VerticalAlignment="Top" Width="231" Grid.Column="1"/>
<Button x:Name="CreateGridBtn" Grid.Column="1" Content="Create Grid" HorizontalAlignment="Left" Margin="311,14,0,0" VerticalAlignment="Top" Click="CreateGridBtn_Click"/>
<Canvas Width="800" Height="800" Grid.ColumnSpan="2" Margin="49,15,51,27" Grid.Row="1" Background="DarkSeaGreen" Grid.RowSpan="2">
<ItemsControl Name="tilesItemsControl" ItemsSource="{Binding Tiles}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Canvas>
<Rectangle
Width="15"
Height="15"
Fill="{Binding Color}"
Canvas.Left ="{Binding ConvertedXLoc}"
Canvas.Top="{Binding ConvertedYLoc}" />
</Canvas>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<ItemsControl Name="ArtistItemsControl" ItemsSource="{Binding Artists}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Canvas>
<Rectangle
Width="3.75"
Height="3.75"
Fill="Black"
Canvas.Left ="{Binding ConvertedXLoc}"
Canvas.Top="{Binding ConvertedYLoc}" />
</Canvas>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Canvas>
<Grid/>
<Button Content="Button" HorizontalAlignment="Left" Margin="4,0,0,0" Grid.Row="2" VerticalAlignment="Center" Click="Button_Click"/>
</Grid>
So with the press of the button I added for testing purposes. It changes a value in the List and then the PropertyChanged method should detect that but it doesn't detect it it just skips it.
Question
So my basic question is, how do I detect the change of a property from objects out of the List of Artists.

OnPropertyChanged will only be executed when the property itself is changed. A new item in a list is not a property change. That's the reason why no updates happens.
Instead a List, try an ObservableCollection. An ObservableCollection implements an additional INotifyCollectionChanged which makes the UI able to react on changing items in the list.

Simple DataBinding in wpf application

Hi I am trying to study simple data binding in wpf. I tried and am not succeeding.. please suggest ways..
<Window x:Class="WpfTestApp.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="250" Width="350">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="70"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="50"/>
<RowDefinition Height="50"/>
<RowDefinition Height="50"/>
<RowDefinition Height="50"/>
</Grid.RowDefinitions>
<Label Content="First Name" Grid.Row="0" Grid.Column="0" Height="25" HorizontalAlignment="Stretch"/>
<Label Content="Last Name" Grid.Row="1" Grid.Column="0" Height="25" HorizontalAlignment="Stretch"/>
<Label Content="Full Name" Grid.Row="2" Grid.Column="0" Height="25" HorizontalAlignment="Stretch"/>
<TextBox x:Name="fName" Text="{Binding FirstName, UpdateSourceTrigger=PropertyChanged}" Grid.Row="0" Grid.Column="1" Height="25" HorizontalAlignment="Stretch"/>
<TextBox x:Name="lName" Text="{Binding LastName, UpdateSourceTrigger=PropertyChanged}" Grid.Row="1" Grid.Column="1" Height="25" HorizontalAlignment="Stretch"/>
<Label x:Name="lblFullName" Content="{Binding FirstName}" Grid.Row="2" Grid.Column="1" Height="25" HorizontalAlignment="Stretch"/>
<Button x:Name="cmdCommand" Content="Command" Grid.Row="3" Grid.Column="1" Margin="2" VerticalAlignment="Center" HorizontalAlignment="Center" Click="cmdCommand_Click"/>
</Grid>
</Window>
Now you see, I want that the label lblFullName to be automatically updated as soon as I type name in textboxes.
Now the my codebehind file looks like this:
public partial class MainWindow : Window, INotifyPropertyChanged
{
private string _firstName;
public string FirstName
{
get { return _firstName; }
set
{
if (value != _firstName)
{
_firstName = value;
OnPropertyChanged("FirstName");
}
}
}
private string _lastName;
public string LastName
{
get { return _lastName; }
set
{
if (value != _lastName)
{
_lastName = value;
OnPropertyChanged("LastName");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Notifies objects registered to receive this event that a property value has changed.
/// </summary>
/// <param name="propertyName">The name of the property that was changed.</param>
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public MainWindow()
{
InitializeComponent();
}
private void cmdCommand_Click(object sender, RoutedEventArgs e)
{
lblFullName.Content = FirstName + " " + LastName;
}
}
needless to say, even clicking the command button is not working...
any suggestions?

Setting the DataContext to point to the window itself will solve the immediate problem:
public MainWindow()
{
InitializeComponent();
this.DataContext = this;
}
The paths in the Binding expressions in the Xaml are all relative to the DataContext of the controls so the DataContext has to be set.
However, I strongly suggest that you put the first name and last name in a separate class (e.g. PersonViewModel) That will make the code easier to read and to maintain.
public class PersonViewModel : INotifyPropertyChanged
{
private string _firstName;
public string FirstName
{
get { return _firstName; }
set
{
if (value != _firstName)
{
_firstName = value;
OnPropertyChanged("FirstName");
}
}
}
private string _lastName;
public string LastName
{
get { return _lastName; }
set
{
if (value != _lastName)
{
_lastName = value;
OnPropertyChanged("LastName");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new PersonViewModel();
}
private void cmdCommand_Click(object sender, RoutedEventArgs e)
{
lblFullName.Content = FirstName + " " + LastName;
}
}
Now the last part of this code does not work anymore. There are two solutions.
The quick and dirty solution:
private void cmdCommand_Click(object sender, RoutedEventArgs e)
{
var person = this.DataContext as PersonViewModel;
if(person == null) return;
lblFullName.Content = string.Format("{0} {1}", person.FirstName, person.LastName);
}
A better way, when trying to do proper MVVM is to put an extra property in the ViewModel (note the change in the First and Last name properties!):
public class PersonViewModel : INotifyPropertyChanged
{
public string FullName
{
get
{
return string.Format("{0} {1}", FirstName, LastName);
}
}
private string _firstName;
public string FirstName
{
get { return _firstName; }
set
{
if (value != _firstName)
{
_firstName = value;
OnPropertyChanged("FirstName");
OnPropertyChanged("FullName");
}
}
}
private string _lastName;
public string LastName
{
get { return _lastName; }
set
{
if (value != _lastName)
{
_lastName = value;
OnPropertyChanged("LastName");
OnPropertyChanged("FullName");
}
}
}
// remainder of the class remains the same
}
Remove the button and its click handler. Bind the label to this new property:
<Label Content="{Binding FullName}"
Grid.Row="2" Grid.Column="1"
Height="25" HorizontalAlignment="Stretch"/>

How to share Database within pages in Windows Phone 8?

I am creating a to do list application. At the moment I want to add a new to do list from todolistPage.xaml and after adding, I want to take the data to be able to view in the MainPage.xaml . I am able to view it from the todolistPage but not sure how to bring it to to another page. Hope to have some help. Thanks.
Below are my codes
MainPage.xaml.cs
namespace PivotApp3
{
public partial class MainPage : PhoneApplicationPage
{
// Constructor
public MainPage()
{
InitializeComponent();
// Set the data context of the listbox control to the sample data
DataContext = App.ViewModel;
// Sample code to localize the ApplicationBar
//BuildLocalizedApplicationBar();
}
// Load data for the ViewModel Items
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (!App.ViewModel.IsDataLoaded)
{
App.ViewModel.LoadData();
}
}
private void LongListSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var si = mLongListSelector.SelectedItem as PivotApp3.ViewModels.ItemViewModel;
if (mLongListSelector.SelectedItem == null)
return;
if (si.LineOne.Equals("+ To Do List"))
NavigationService.Navigate(new Uri("/todolistPage.xaml", UriKind.Relative));
else if (si.LineOne.Equals("+ Reminder"))
NavigationService.Navigate(new Uri("/reminderPage.xaml", UriKind.Relative));
// Reset selected item to null (no selection)
mLongListSelector.SelectedItem = null;
}
}
MainPage.xaml
<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
<!-- LOCALIZATION NOTE:
To localize the displayed strings copy their values to appropriately named
keys in the app's neutral language resource file (AppResources.resx) then
replace the hard-coded text value between the attributes' quotation marks
with the binding clause whose path points to that string name.
For example:
Text="{Binding Path=LocalizedResources.ApplicationTitle, Source={StaticResource LocalizedStrings}}"
This binding points to the template's string resource named "ApplicationTitle".
Adding supported languages in the Project Properties tab will create a
new resx file per language that can carry the translated values of your
UI strings. The binding in these examples will cause the value of the
attributes to be drawn from the .resx file that matches the
CurrentUICulture of the app at run time.
-->
<!--Pivot Control-->
<phone:Pivot Title="DAILY ROUTINE">
<!--Pivot item one-->
<phone:PivotItem Header="activity">
<!--Double line list with text wrapping-->
<phone:LongListSelector x:Name="mLongListSelector" Margin="0,0,-12,0" ItemsSource="{Binding Items}" SelectionChanged="LongListSelector_SelectionChanged">
<phone:LongListSelector.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0,0,0,17">
<TextBlock Text="{Binding LineOne}" TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}"/>
</StackPanel>
</DataTemplate>
</phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>
</phone:PivotItem>
<!--Pivot item two-->
<phone:PivotItem Header="today">
</phone:PivotItem>
</phone:Pivot>
<!--Uncomment to see an alignment grid to help ensure your controls are
aligned on common boundaries. The image has a top margin of -32px to
account for the System Tray. Set this to 0 (or remove the margin altogether)
if the System Tray is hidden.
Before shipping remove this XAML and the image itself.-->
<!--<Image Source="/Assets/AlignmentGrid.png" VerticalAlignment="Top" Height="800" Width="480" Margin="0,-32,0,0" Grid.Row="0" IsHitTestVisible="False" />-->
</Grid>
todolistPage.xaml.cs
namespace PivotApp3
{
public partial class todolistPage : PhoneApplicationPage, INotifyPropertyChanged
{
// Data context for the local database
private ToDoDataContext toDoDB;
// Define an observable collection property that controls can bind to.
private ObservableCollection<ToDoItem> _toDoItems;
public ObservableCollection<ToDoItem> ToDoItems
{
get
{
return _toDoItems;
}
set
{
if (_toDoItems != value)
{
_toDoItems = value;
NotifyPropertyChanged("ToDoItems");
}
}
}
//constructor
public todolistPage()
{
InitializeComponent();
// Connect to the database and instantiate data context.
toDoDB = new ToDoDataContext(ToDoDataContext.DBConnectionString);
// Data context and observable collection are children of the main page.
this.DataContext = this;
}
private void deleteTaskButton_Click(object sender, RoutedEventArgs e)
{
// Cast parameter as a button.
var button = sender as Button;
if (button != null)
{
// Get a handle for the to-do item bound to the button.
ToDoItem toDoForDelete = button.DataContext as ToDoItem;
// Remove the to-do item from the observable collection.
ToDoItems.Remove(toDoForDelete);
// Remove the to-do item from the local database.
toDoDB.ToDoItems.DeleteOnSubmit(toDoForDelete);
// Save changes to the database.
toDoDB.SubmitChanges();
// Put the focus back to the main page.
this.Focus();
}
}
private void newToDoTextBox_GotFocus(object sender, RoutedEventArgs e)
{
// Clear the text box when it gets focus.
newToDoTextBox.Text = String.Empty;
}
private void newToDoAddButton_Click(object sender, RoutedEventArgs e)
{
// Create a new to-do item based on the text box.
ToDoItem newToDo = new ToDoItem { ItemName = newToDoTextBox.Text };
// Add a to-do item to the observable collection.
ToDoItems.Add(newToDo);
// Add a to-do item to the local database.
toDoDB.ToDoItems.InsertOnSubmit(newToDo);
}
protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
{
// Call the base method.
base.OnNavigatedFrom(e);
// Save changes to the database.
toDoDB.SubmitChanges();
}
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
// Define the query to gather all of the to-do items.
var toDoItemsInDB = from ToDoItem todo in toDoDB.ToDoItems
select todo;
// Execute the query and place the results into a collection.
ToDoItems = new ObservableCollection<ToDoItem>(toDoItemsInDB);
// Call the base method.
base.OnNavigatedTo(e);
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
// Used to notify the app that a property has changed.
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
public class ToDoDataContext : DataContext
{
// Specify the connection string as a static, used in main page and app.xaml.
public static string DBConnectionString = "Data Source=isostore:/ToDo.sdf";
// Pass the connection string to the base class.
public ToDoDataContext(string connectionString)
: base(connectionString)
{ }
// Specify a single table for the to-do items.
public Table<ToDoItem> ToDoItems;
}
[Table]
public class ToDoItem : INotifyPropertyChanged, INotifyPropertyChanging
{
// Define ID: private field, public property and database column.
private int _toDoItemId;
[Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)]
public int ToDoItemId
{
get
{
return _toDoItemId;
}
set
{
if (_toDoItemId != value)
{
NotifyPropertyChanging("ToDoItemId");
_toDoItemId = value;
NotifyPropertyChanged("ToDoItemId");
}
}
}
// Define item name: private field, public property and database column.
private string _itemName;
[Column]
public string ItemName
{
get
{
return _itemName;
}
set
{
if (_itemName != value)
{
NotifyPropertyChanging("ItemName");
_itemName = value;
NotifyPropertyChanged("ItemName");
}
}
}
// Define completion value: private field, public property and database column.
private bool _isComplete;
[Column]
public bool IsComplete
{
get
{
return _isComplete;
}
set
{
if (_isComplete != value)
{
NotifyPropertyChanging("IsComplete");
_isComplete = value;
NotifyPropertyChanged("IsComplete");
}
}
}
// Version column aids update performance.
[Column(IsVersion = true)]
private Binary _version;
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
// Used to notify the page that a data context property changed
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
#region INotifyPropertyChanging Members
public event PropertyChangingEventHandler PropertyChanging;
// Used to notify the data context that a data context property is about to change
private void NotifyPropertyChanging(string propertyName)
{
if (PropertyChanging != null)
{
PropertyChanging(this, new PropertyChangingEventArgs(propertyName));
}
}
#endregion
}
todolistPage.xaml
<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<!--TitlePanel contains the name of the application and page title-->
<StackPanel Grid.Row="0" Margin="12,17,0,28">
<TextBlock Text="TO DO LIST" Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock Text="add" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
</StackPanel>
<!-- Bind the list box to the observable collection. -->
<ListBox x:Name="toDoItemsListBox" ItemsSource="{Binding ToDoItems}"
Grid.Row="1" Margin="12,0,28,210" Width="440">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid HorizontalAlignment="Stretch" Width="440">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="50" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="100" />
</Grid.ColumnDefinitions>
<CheckBox
IsChecked="{Binding IsComplete, Mode=TwoWay}"
Grid.Column="0"
VerticalAlignment="Center"/>
<TextBlock
Text="{Binding ItemName}"
FontSize="{StaticResource PhoneFontSizeLarge}"
Grid.Column="1"
VerticalAlignment="Center"/>
<Button
Grid.Column="2"
x:Name="deleteTaskButton"
BorderThickness="0"
Margin="0"
Click="deleteTaskButton_Click">
<Image Source="appbar.delete.rest.png"/>
</Button>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<!--ContentPanel - place additional content here-->
<Grid x:Name="ContentPanel" Grid.Row="2" Margin="12,465,12,0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="10*"/>
<ColumnDefinition Width="9*"/>
</Grid.ColumnDefinitions>
<TextBox
x:Name="newToDoTextBox"
Grid.Column="0"
Text="add new task"
FontFamily="{StaticResource PhoneFontFamilyLight}"
GotFocus="newToDoTextBox_GotFocus" Margin="0,-65,0,104" Grid.ColumnSpan="2"/>
<Button
Content="add"
x:Name="newToDoAddButton"
Click="newToDoAddButton_Click" Margin="150,43,130,10" Grid.ColumnSpan="2"/>
</Grid>
</Grid>
Database Created
using (ToDoDataContext db = new ToDoDataContext(ToDoDataContext.DBConnectionString))
{
if (db.DatabaseExists() == false)
{
//Create the database
db.CreateDatabase();
}
}

Put your database into App.xaml.cs:
// Data context for the local database
public ToDoDataContext toDoDB;
add this code to App.xaml.cs:
public new static App Current
{
get
{
return (App)Application.Current;
}
}
Then you can access your database everywhere by using:
App.Current.toDoDB...

You can create class to manipulate data in sql and make it avaiable from App.xaml.cs
Here is sample code
ToDoDataViewModel class:
public class ToDoDataViewModel : INotifyPropertyChanged
{
ToDoDataContext db;
public ToDoDataViewModel(string connectionString)
{
db = new ToDoDataContext(connectionString);
}
private ObservableCollection<ToDoItem> _toDoItems;
public ObservableCollection<ToDoItem> ToDoItems
{
get { return this._toDoItems; }
set
{
this._toDoItems = value;
NotifyPropertyChanged("ToDoItems");
}
}
public void LoadCollectionsFromDatabase()
{
var toDos = from todo in db.ToDoItems
select todo;
_toDoItems = new ObservableCollection<ToDoItem>(toDos);
}
public void InsertToDoItem(ToDoItem item)
{
db.ToDoItems.InsertOnSubmit(item);
_toDoItems.Add(item);
db.SubmitChanges();
}
public void DeleteToDoItem(ToDoItem item)
{
db.ToDoItems.DeleteOnSubmit(item);
_toDoItems.Remove(item);
db.SubmitChanges();
}
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
In App.xaml.cs:
public partial class App : Application
{
private static ToDoDataViewModel _viewModel;
public static ToDoDataViewModel ViewModel
{
get { return _viewModel; }
}
//other methods of App
public App()
{
//place this code at the and of the contructor
CreateDb();
}
private void CreateDb()
{
using(var db=new ToDoDataContext(ToDoDataContext.DBConnectionString))
{
if(!db.DatabaseExists())
{
db.CreateDatabase();
}
}
_viewModel=new ToDoDataViewModel(ToDoDataContext.DBConnectionString);
_viewModel.LoadCollectionsFromDatabase();
}
}
And place this code in the constructors of your pages:
this.DataContext=App.ViewModel;
This way you separated your database logic from application logic
Now you can update your newToDoAddButton_Click method as following:
private void newToDoAddButton_Click(object sender, RoutedEventArgs e)
{
// Create a new to-do item based on the text box.
ToDoItem newToDo = new ToDoItem { ItemName = newToDoTextBox.Text };
//Add to-do item to the local database
App.ViewModel.InsertToDoItem(newToDo);
this.Focus();
}
And your deleteTaskButton_Click method:
private void deleteTaskButton_Click(object sender, RoutedEventArgs e)
{
var button = sender as Button;
if (button != null)
{
// Get a handle for the to-do item bound to the button.
ToDoItem toDoForDelete = button.DataContext as ToDoItem;
// Remove the to-do item from the local database.
App.ViewModel.DeleteToDoItem(toDoForDelete);
this.Focus();
}
}

MVVM viewmodel events (commands?)

I have a MVVM setup that creates a View on my MainWindow. I am not sure how to know when a user Clicks on a specific Notification Item inside the View. Where would I add the event, or a command to know when that happens?
here are is my MVVM code :
MainWindow
cs:
NotificationViewModel notificationViewModel = new NotificationViewModel();
notificationViewModel.AddNoticiation(new NotificationModel() { Message = "Error", Name = "Station 21" });
NotificationView.DataContext = notificationViewModel;
xaml:
<notification:NotificationView x:Name="NotificationView" />
NotificationModel
public class NotificationModel : INotifyPropertyChanged
{
private string _Message;
public string Message
{
get { return _Message; }
set
{
if (_Message != value)
{
_Message = value;
RaisePropertyChanged("Message");
}
}
}
private string _Name;
public string Name
{
get { return _Name; }
set
{
if (_Name != value)
{
_Name = value;
RaisePropertyChanged("Name");
}
}
}
public string TimeStamp
{
get { return DateTime.Now.ToString("h:mm:ss"); }
}
#region PropertChanged Block
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
#endregion
}
NotificationViewModel
public class NotificationViewModel
{
private ObservableCollection<NotificationModel> _Notifications = new ObservableCollection<NotificationModel>();
public ObservableCollection<NotificationModel> Notifications
{
get { return _Notifications; }
set { _Notifications = value; }
}
public void AddNoticiation(NotificationModel notification)
{
this.Notifications.Insert(0, notification);
}
}
NotificationView
<Grid>
<StackPanel HorizontalAlignment="Left" >
<ItemsControl ItemsSource="{Binding Path=Notifications}"
Padding="5,5,5,5">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Background="SlateGray"
CornerRadius="4">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100" />
<ColumnDefinition Width="100" />
<ColumnDefinition Width="100" />
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0"
Text="{Binding Path=TimeStamp}" />
<TextBlock Grid.Column="1"
Text="{Binding Path=Name}" />
<TextBlock Grid.Column="2"
Text="{Binding Path=Message}" />
</Grid>
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
</Grid>

There's no real selection mechanism built into an ItemsControl. It would probably solve your problem to switch out your ItemsControl for a ListBox.
If you do that, you can bind to SelectedItem, then handle any changes made to SelectedItem using the PropertyChanged event.
Example:
In your view model's constructor:
PropertyChanged += NotificationViewModel_PropertyChanged;
Add a property to your view model to allow the binding:
private string _selectedNotification;
public string SelectedNotification
{
get { return _selectedNotification; }
set
{
if (_selectedNotification != value)
{
_selectedNotification = value;
RaisePropertyChanged("SelectedNotification");
}
}
}
Finally, add the event handler to your view model:
NotificationViewModel_PropertyChanged(object sender, PropertyChangedEventArgs e))
{
if (e.PropertyName = "SelectedNotification") DoStuff();
}
You may find that you don't even need to hook into PropertyChanged if you just want to update another control in your view based on the selected item in your list box. You can just bind directly to the property within xaml.

How to bind usercontrols in xaml?

I have MainWindow containing a datagrid and a "filter panel". The filter panel can change by a user input(button click). I try to achieve it with databinding. The problem that Im facing is the filter panel(which is a user control) is not loaded or refreshed.
Mainwindow xaml:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="250*" />
<ColumnDefinition Width="253*" />
</Grid.ColumnDefinitions>
<DataGrid AutoGenerateColumns="True" Height="200" HorizontalAlignment="Left" Margin="23,28,0,0" Name="dataGrid1" VerticalAlignment="Top" Width="200" ItemsSource="{Binding OverviewableItems}" />
<UserControl Grid.Column="1" Content="{Binding UserControl}" DataContext="{Binding}" Grid.ColumnSpan="2" />
<Button Content="PersonFilter" Height="23" HorizontalAlignment="Left" Margin="23,268,0,0" Name="buttonPersonFilter" VerticalAlignment="Top" Width="75" Click="buttonPersonFilter_Click" />
<Button Content="ProjectFilter" Height="23" HorizontalAlignment="Left" Margin="132,268,0,0" Name="buttonProjectFilter" VerticalAlignment="Top" Width="75" Click="buttonProjectFilter_Click" />
</Grid>
code behind:
private ViewModel _viewModel;
public MainWindow()
{
_viewModel = new ViewModel(new DataProvider());
DataContext = _viewModel;
_viewModel.PropertyChanged += _viewModel.SetFilterType;
InitializeComponent();
}
private void buttonProjectFilter_Click(object sender, RoutedEventArgs e)
{
_viewModel.OverviewType = OverviewType.Project;
}
private void buttonPersonFilter_Click(object sender, RoutedEventArgs e)
{
_viewModel.OverviewType = OverviewType.Person;
}
First user control:
<Grid>
<DatePicker Grid.Column="1" Grid.Row="1" Height="25" HorizontalAlignment="Left" Margin="19,18,0,0" Name="datePickerFundingTo" VerticalAlignment="Top" Width="115" Text="{Binding ElementName=ProjectFilter, Path=FundingTo}" />
</Grid>
code behind for this user control is only this:
public DateTime FundingTo { get; set; }
public ProjectFilter()
{
FundingTo = DateTime.Now;
InitializeComponent();
}
Other user control: just simply contains a TextBox and a Button, for the sake of simplicity I didnt add any code behind to it.
ViewModel of the MainWindow:
public class ViewModel : INotifyPropertyChanged
{
private UserControl _userControl;
public UserControl UserControl
{
get { return _userControl; }
set
{
if (_userControl == value)
{
return;
}
OnPropertyChanged("UserControl");
_userControl = value;
}
}
private OverviewType _overviewType = OverviewType.None;
public OverviewType OverviewType
{
get { return _overviewType; }
set
{
if (_overviewType == value)
{
return;
}
OnPropertyChanged("OverviewType");
_overviewType = value;
}
}
private ObservableCollection<IOverviewItem> _overviewableItems;
public ObservableCollection<IOverviewItem> OverviewableItems
{
get { return _overviewableItems; }
set
{
if (_overviewableItems == value)
{
return;
}
_overviewableItems = value;
}
}
private readonly DataProvider _dataProvider;
public event PropertyChangedEventHandler PropertyChanged;
public ViewModel(DataProvider dataProvider)
{
_dataProvider = dataProvider;
}
public void SetFilterType(object sender, EventArgs eventArgs)
{
switch (_overviewType)
{
case OverviewType.Project:
_userControl = new ProjectFilter();
break;
case OverviewType.Person:
_userControl = new PersonFilter();
break;
}
}
public void OnPropertyChanged(string name)
{
if (PropertyChanged == null)
return;
var eventArgs = new PropertyChangedEventArgs(name);
PropertyChanged(this, eventArgs);
}
}
plus I have an enum OverviewType with None,Project,Person values.
The property changed event fired properly, but the user control is not refreshed. Could anyone enlight me, where is the flaw in my solution?
And the other question I have, how can I communicate from the usercontrols to the mainwindow viewmodel? Forex: the datagrid should be changed according to its filter.
Any help would be greatly appreciated. Cheers!

There are different problems here.
As Clemens said, you must fire your event after the value is updated. But it's not the main issue here.
Second problem: you are affecting your new usercontrol to the private member, so you're totally bypassing your property.
Replace
_userControl = new ProjectFilter();
by
this.UserControl = new ProjectFilter();
Third problem, which is not directly related to your question but actually is your biggest problem: you have an architecture design issue. You're exposing in your viewmodel a UserControl, which is an anti-pattern. Your viewmodel must not know anything about the view, so it must NOT have any reference to the controls inside the view. Instead of the binding you wrote, you could fire an event from the viewmodel and add an event handler in your view so it's your view that updates the usercontrol.

Try to fire the PropertyChanged after changing a property's backing field:
public UserControl UserControl
{
get { return _userControl; }
set
{
if (_userControl != value)
{
_userControl = value; // first
OnPropertyChanged("UserControl"); // second
}
}
}
Similar for OverviewType.