This is not a question, but stating a fact. Here's a simple test program. DataItem has an indexed property. MainPage uses an instance of this class as a data context. When I click the button, DataContext is set to null. When I bind to textboxes via indexed
property, programme crashes with AccessViolationException after clicking the button. When I bind via wrapped properties Prop1 and Prop2, values disappear from controls and there is no crash, as expected. Is this an error or by definition? I am really glad
I was able to isolate this problem, these crashes were driving me mad and I could not find out why. I wanted to save myself a bit of coding with indexed properties, but it looks like I have to rewrap them with normal properties and save myself a
headache :)
Ivan
public class DataItem : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string property)
{
if(PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
Dictionary<int, int> _Values;
public int Prop1
{
get { return this[1]; }
set { this[1] = value; RaisePropertyChanged("Prop1"); }
}
public int Prop2
{
get { return this[2]; }
set { this[2] = value; RaisePropertyChanged("Prop2"); }
}
public int this[int index]
{
get
{
int value;
if (_Values == null)
_Values = new Dictionary<int, int>();
if (!_Values.TryGetValue(index, out value))
_Values[index] = value = 0;
return value;
}
set
{
if (this[index] != value)
{
_Values[index] = value;
RaisePropertyChanged("item[]");
}
}
}
}
MainPage.xaml.cs:
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
DataContext = new DataItem();
}
/// <summary>
/// Invoked when this page is about to be displayed in a Frame.
/// </summary>
/// <param name="e">Event data that describes how this page was reached. The Parameter
/// property is typically used to configure the page.</param>
protected override void OnNavigatedTo(NavigationEventArgs e)
{
}
private void Button_Click(object sender, RoutedEventArgs e)
{
DataContext = null;
}
}
and XAML:
<Page
x:Class="Indexed.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Indexed"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
<StackPanel Orientation="Vertical" >
<TextBox Text="{Binding [1], Mode=TwoWay}"/>
<TextBox Text="{Binding [2], Mode=TwoWay}"/>
<!--<TextBox Text="{Binding Prop1, Mode=TwoWay}"/>
<TextBox Text="{Binding Prop2, Mode=TwoWay}"/>-->
<Button Content="Crash!" Click="Button_Click"/>
</StackPanel>
</Grid>
</Page>
