Develop Reference

File path to file name String converter not working

Using a wpf ListBox I'm trying to display a list of filename without displaying the full path (more convenient for user).
Data comes from an ObservableCollection which is filled using Dialog.
private ObservableCollection<string> _VidFileDisplay = new ObservableCollection<string>(new[] {""});
public ObservableCollection<string> VidFileDisplay
{
get { return _VidFileDisplay; }
set { _VidFileDisplay = value; }
}
In the end I want to select some items and get back the full file path. For this I have a converter :
public class PathToFilenameConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
//return Path.GetFileName(value.ToString());
string result = null;
if (value != null)
{
var path = value.ToString();
if (string.IsNullOrWhiteSpace(path) == false)
result = Path.GetFileName(path);
}
return result;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return value;
}
}
Which I bind to my listbox itemsource :
<ListBox x:Name="VideoFileList" Margin="0" Grid.Row="1" Grid.RowSpan="5" Template="{DynamicResource BaseListBoxControlStyle}" ItemContainerStyle="{DynamicResource BaseListBoxItemStyle}" ScrollViewer.HorizontalScrollBarVisibility="Disabled" ItemsSource="{Binding Path=DataContext.VidFileDisplay, Converter={StaticResource PathToFileName},ElementName=Ch_Parameters, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" SelectedItem="{Binding Path=SelectedVidNames,ElementName=Ch_Parameters, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
Without the converter, it is working fine (but of course this is the full path displayed in the listbox). With the converter I have one character per line... displaying this :
System.Collections.ObjectModel.ObservableCollection`1[System.String]
Where am I wrong ?
Thank you

In ItemsSource binding converter applies to the whole list and not to each item in the collection. If you want to apply your converter per item you need to do it ItemTemplate
<ListBox x:Name="VideoFileList" ItemsSource="{Binding Path=DataContext.VidFileDisplay, ElementName=Ch_Parameters}" ...>
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=., Converter={StaticResource PathToFileName}}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

Binding items in ListBox in WP8

In a Windows Phone 8 app,
I have a listbox with 2 TextBlocks and a button.
I have a list of 2 strings and a boolean & I am able to bind the strings to the TextBlocks.
<ListBox Name="ListboxTest">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Key}" TextWrapping="Wrap"/>
<TextBlock Text="{Binding Value}" TextWrapping="Wrap"/>
<Button />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
And this is the C# code to bind to the list box.
public class Detail
{
public string Key { get; set; }
public string Value { get; set; }
public bool check { get; set; }
}
public List<Detail> ClassList = new List<Detail>();
ListboxTest.ItemsSource = ClassList;
I want to display the button only when the boolean value is true.
How do I do it?

Take a look at this. Actually what you really need is a Converter by implementing the IValueConverter. This is also a good example where you could read about it. Bind the boolean value with the visibility property of the button and you are done! ;)

You can use boolean to visibility converter to hide, show button
Here are example:
public class BoolToVisibility : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var boolValue = false;
if (value != null) boolValue = (bool)value;
return boolValue ? Visibility.Visible : Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
In app.xaml
<my:BoolToVisibility x:Key="BoolToVisibility"/>
In your data template
<Button Visibility="{Binding Path=YourBoolProperty,Converter={StaticResource BoolToVisibility}}>

Or, you could add this property to the Detail class:
public Visibility ButtonVisibility {
get {
return this.check == true ? Visibility.Visible : Visibility.Collapsed;
}
}
And then just bind the button's Visibility to the ButtonVisibility property without any converters.
<Button Visibility="{Binding ButtonVisibility}" />

Please try those use Triggers.
Various Triggers in windows phone Msdn.
Please use ObservableCollection in WP8 for binding instead of List.
Please make your properties are implemented with INotifyPropertyChanged If your Boolean property is not implemented with inotifypropertychanged the view will not know the value is changed.hence the Data trigger will not work.
Namespace
xmlns:interactivity="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
xmlns:ec="clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions"
x:Class="XXX_XXXX"
<Button Content="My button"
Stretch="None"
HorizontalAlignment="Stretch"
VerticalAlignment="Top">
<interactivity:Interaction.Triggers>
<ec:DataTrigger Binding="{Binding Check}" Value="True">
<ec:ChangePropertyAction PropertyName="Visibility">
<ec:ChangePropertyAction.Value>
<Visibility>Visible</Visibility>
</ec:ChangePropertyAction.Value>
</ec:ChangePropertyAction>
</ec:DataTrigger>
<ec:DataTrigger Binding="{Binding Check}" Value="False">
<ec:ChangePropertyAction PropertyName="Visibility">
<ec:ChangePropertyAction.Value>
<Visibility>Collapsed</Visibility>
</ec:ChangePropertyAction.Value>
</ec:ChangePropertyAction>
</ec:DataTrigger>
</interactivity:Interaction.Triggers>
</Button>
Note Answered from phone syntax may not be correct

WPF Visibility Binding to Converted Instance Property

So I have a button. I want to set the visibility of the button according to the value of an integer property of a class. This requires a data binding and a converter.
The XAML code for the button is as follows:
<Window.Resources>
<local:Button1VisibilityConverter x:Key="Button1VisibilityConverter"/>
<local:ModeValues x:Key="ModeHolder"/>
</Window.Resources>
<Grid>
<StackPanel HorizontalAlignment="Left" Height="150" Margin="92,90,0,0" VerticalAlignment="Top" Width="301">
<Button Content="1" Height="58" Background="#FFA20000" Foreground="White" Visibility="{Binding Source={StaticResource ModeHolder}, Path=State, Converter=Button1VisibilityConverter}"/>
<Button Content="2" Height="58" Background="#FF16A200" Foreground="White"/>
<Button Content="3" Height="58" Background="#FF4200A2" Foreground="White"/>
</StackPanel>
</Grid>
My converter is as follows:
class Button1VisibilityConverter : IValueConverter
{
public object Convert(object value, Type targettype, object parameter, System.Globalization.CultureInfo culture)
{
int mode = (int)value;
if (mode == ModeValues.Red)
return System.Windows.Visibility.Visible;
else
return System.Windows.Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return null;
}
}
The class that has the property I want to control the visibility is as follows:
public class ModeValues : IObservable<int>
{
private int _state = -1;
public static int Red
{
get
{
return 0;
}
}
public static int Green
{
get
{
return 1;
}
}
public static int Purple
{
get
{
return 2;
}
}
public int State
{
get
{
return this._state;
}
set
{
this.State = value;
}
}
}
I have no idea why it isn't working. I thought I had to bind the visibility to the property of the instance of the ModeHolder, make the ModeHolder observable, and convert the int to a visibility. What am I missing?

Converter=Button1VisibilityConverter
should be:
Converter={StaticResource Button1VisibilityConverter}

Conditional element in xaml depending on the binding content

Is it possible to display this TextBlock, only if the Address.Length > 0 ? I'd like to do this directly into the xaml, I know I could put all my controls programmatically
<TextBlock Text="{Binding Path=Address}" />

Basically, you're going to need to write an IValueConverter so that you can bind the Visibility property of your TextBox to either the Address field, or a new field that you create.
If you bind to the Address field, here's how the binding might look like::
<TextBlock Text="{Binding Path=Address}"
Visibility="{Binding Path=Address, Converter={StaticResource StringLengthVisibilityConverter}}" />
And then StringLengthVisiblityConverter could look something like this:
public class StringLengthVisiblityConverter: IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value == null || value.ToString().Length == 0)
{
return Visibility.Collapsed;
}
else
{
return Visibility.Visible;
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
// Don't need to implement this
}
}
Then you'd just need to add your converter as a resource, using syntax like this (where src is mapped to the namespace where the converter is defined):
<src:StringLengthVisiblityConverter x:Key="StringLengthVisiblityConverter" />

I would do this with another boolean property called HasAddress which returns Address.Length > 0.
<!-- In some resources section -->
<BooleanToVisibilityConverter x:Key="Bool2VisibilityConverter" />
<TextBlock
Text="{Binding Address}"
Visibility="{Binding HasAddress, Converter={StaticResource Bool2VisibilityConverter}}"
/>
You should also remember to notify the property change for HasAddress in the setter of Address.

You can create a StringToVisibility converter.
It will return Visibility.Visible if bound string is not null or empty and Visibility.Collapsed if it is.
Use this converter while binding Address with Visibility property of your TextBlock.
Example:
<TextBlock Text="{Binding Path=Address}" Visibility="{Binding Address, Converter={StaticResource StringToVisibilityConverter}}" />

Silverlight: Difficulty with binding to visiblity

I have two elements: a listbox and a "this list is empty" message. I'd like to bind their visibility to the list box's ItemsSource being empty. However, I'm not sure how to do this:
<TextBlock Text="No favorite searches yet. Add some by searching, then clicking 'Add to Favorites'"
Padding="10,0"
VerticalAlignment="Center"
Visibility="{Binding Path=FavoriteFilters.IsEmpty, Converter={StaticResource visibilityConverter}}"
/>
<ListBox ItemsSource="FavoriteFilters"
x:Name="favoriteFiltersList"
Visibility="{Binding Path=FavoriteFilters.IsEmpty, Converter={StaticResource visibilityConverter}}">
<ListBox.ItemTemplate>
<DataTemplate>
<my:FavoriteFilterLink />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
They are both visible, although the ItemsSource is empty. Also, I'm not sure how to invert the condition for the ListBox.
The visibility converter:
public class VisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value is bool?)
{
if (string.IsNullOrEmpty((string)parameter))
{
return (value as bool?).Value ? Visibility.Visible : Visibility.Collapsed;
} else
{
return (value as bool?).Value ? Visibility.Collapsed : Visibility.Visible;
}
}
throw new ArgumentException();
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}

You might be better off writing two converters, one for the ListBox the other for the TextBlock. The logic of each would be simpler and you wouldn't need to pass a parameter to get the correct result.
While it might not be as elegant as a single converter solution it will be far more maintainable.
If you really want to pass a parameter then you need to use the ConverterParameter.
There's an example here but I'm not 100% sure it'll meet your requirements. The simplified XAML syntax is:
<TextBlock Visibility="{Binding FavoriteFilters.IsEmpty,
Converter={StaticResource visibilityConverter}, ConverterParameter=false}"/>
<ListBox Visibility="{Binding FavoriteFilters.IsEmpty,
Converter={StaticResource visibilityConverter}, ConverterParameter=true}"/>
Then in your converter (simplified):
bool show = (bool)value;
bool visible = (bool)parameter;
if (visible)
{
return show ? Visibility.Visible : Visibility.Collapsed;
}
else
{
return show ? Visibility.Collapsed : Visibility.Visible;
}