Develop Reference

XAML: Show button on ComboBox item highlight

I have a ComboBox with an ItemTemplateSelector, using 2 different DataTemplates, one for when its drop down is visible and another when it is not. For the drop down template, each ComboBox item is represented by a TextBlock and a Button that should only be visible whenever that item is focused/highlighted/mouse over. This is what I've tried:
<ComboBox x:Name="Windows" ItemsSource="{Binding Windows}" SelectedItem="{Binding Window}" Focusable="False" MaxDropDownHeight="238">
<ComboBox.ItemTemplateSelector>
<s:ComboBoxItemTemplateSelector>
<s:ComboBoxItemTemplateSelector.SelectedTemplate>
<DataTemplate>
<TextBlock Text="{Binding TitleShort}" ToolTip="{Binding Title}" />
</DataTemplate>
</s:ComboBoxItemTemplateSelector.SelectedTemplate>
<s:ComboBoxItemTemplateSelector.DropDownTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" VerticalAlignment="Center">
<TextBlock Text="{Binding TitleShort}" />
<Button Content="X">
<Button.Style>
<Style TargetType="Button">
<Setter Property="Visibility" Value="Collapsed" />
<Style.Triggers>
<DataTrigger Binding="{Binding IsFocused, ElementName=Windows}" Value="True">
<Setter Property="Visibility" Value="Visible" />
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
</StackPanel>
</DataTemplate>
</s:ComboBoxItemTemplateSelector.DropDownTemplate>
</s:ComboBoxItemTemplateSelector>
</ComboBox.ItemTemplateSelector>
<ComboBox.ItemContainerStyle>
<Style BasedOn="{StaticResource MaterialDesignComboBoxItemStyle}" TargetType="ComboBoxItem">
<Setter Property="ToolTip">
<Setter.Value>
<TextBlock Text="{Binding Title}" />
</Setter.Value>
</Setter>
</Style>
</ComboBox.ItemContainerStyle>
</ComboBox>
public class ComboBoxItemTemplateSelector : DataTemplateSelector
{
public DataTemplate SelectedTemplate { get; set; }
public DataTemplate DropDownTemplate { get; set; }
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
ComboBoxItem comboBoxItem = GetVisualParent<ComboBoxItem>(container);
if (comboBoxItem == null)
{
return SelectedTemplate;
}
return DropDownTemplate;
}
private static T GetVisualParent<T>(object childObject) where T : Visual
{
DependencyObject child = childObject as DependencyObject;
while ((child != null) && !(child is T))
{
child = VisualTreeHelper.GetParent(child);
}
return child as T;
}
}

ComboBox generates ComboBoxItem as a container for every item in its itemssource. You can bind to its properties with RelativeSource binding.
This should get you the expected behavior:
<Button Content="X">
<Button.Style>
<Style TargetType="Button">
<Setter Property="Visibility" Value="Collapsed" />
<Style.Triggers>
<DataTrigger Binding="{Binding IsMouseOver, RelativeSource={RelativeSource AncestorType=ComboBoxItem}}" Value="True">
<Setter Property="Visibility" Value="Visible" />
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>

Pass Color to IValueConverter

I am making a WPF application using the MVVM design pattern. Part of the app is a signal strength bar. We created it with just a rectangular user control and created a 4 column grid, so all we need to do is change either the background or foreground color of the control.
My idea on how to do this is a simply store Boolean values for each of the 4 sections and use a value converter. However, there are 3 instances of this control, each with a different color. How can I pass the needed color into the converter? I know converters have a parameter argument, but I haven't been able to find any examples using it, so I'm not even sure if the parameter argument is what I'm looking for.

Your case may not be best addressed by the method you've chosen (it makes it hard to parameterize the colors of the segments), but your specific question is a good one, so I'll answer it.
As you've found, it's tough to pass anything but a string to ConverterParameter. but you don't have to. If you derive a converter from MarkupExtension, you can assign named and typed properties when you use it, and also not have to create it as a resource (indeed, creating it as a resource would break the thing, since that would be a shared instance and the properties are initialized when it's created). Since the XAML parser knows the types of the properties declared on the class, it will apply the default TypeConverter for Brush, and you'll get the exact same behavior as if you were assigning "PapayaWhip" to "Border.Background" or anything else.
This works with any type, of course, not just Brush.
namespace HollowEarth.Converters
{
public class BoolBrushConverter : MarkupExtension, IValueConverter
{
public Brush TrueBrush { get; set; }
public Brush FalseBrush { get; set; }
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return System.Convert.ToBoolean(value) ? TrueBrush : FalseBrush;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
return this;
}
}
}
Usage:
<TextBox
xmlns:hec="clr-namespace:HollowEarth.Converters"
Foreground="{Binding MyFlagProp, Converter={hec:BoolBrushConverter TrueBrush=YellowGreen, FalseBrush=DodgerBlue}}"
/>
You could give BoolBrushConverter a constructor that takes parameters, too.
public BoolBrushConverter(Brush tb, Brush fb)
{
TrueBrush = tb;
FalseBrush = fb;
}
And in XAML...
<TextBox
xmlns:hec="clr-namespace:HollowEarth.Converters"
Foreground="{Binding MyFlagProp, Converter={hec:BoolBrushConverter YellowGreen, DodgerBlue}}"
/>
I don't think that's a good fit for this case. But sometimes the semantics are so clear, the property name is unnecessary. {hec:GreaterThan 4.5}, for example.
UPDATE
Here's a complete implementation of a SignalBars control. This has five segments to your four, but you can easily remove one; that's only in the template, and the Value property is a double that could be subdivided any way you like (again, in the template).
SignalBars.cs
using System;
using System.ComponentModel;
using System.Windows.Media;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Markup;
namespace HollowEarth
{
public class SignalBars : ContentControl
{
static SignalBars()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(SignalBars), new FrameworkPropertyMetadata(typeof(SignalBars)));
}
#region Value Property
public double Value
{
get { return (double)GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
public static readonly DependencyProperty ValueProperty =
DependencyProperty.Register("Value", typeof(double), typeof(SignalBars),
new PropertyMetadata(0d));
#endregion Value Property
#region InactiveBarFillBrush Property
[Bindable(true)]
[Category("Appearance")]
[DefaultValue("White")]
public Brush InactiveBarFillBrush
{
get { return (Brush)GetValue(InactiveBarFillBrushProperty); }
set { SetValue(InactiveBarFillBrushProperty, value); }
}
public static readonly DependencyProperty InactiveBarFillBrushProperty =
DependencyProperty.Register("InactiveBarFillBrush", typeof(Brush), typeof(SignalBars),
new FrameworkPropertyMetadata(Brushes.White));
#endregion InactiveBarFillBrush Property
}
public class ComparisonConverter : MarkupExtension, IMultiValueConverter
{
public virtual object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (values.Length != 2)
{
throw new ArgumentException("Exactly two values are expected");
}
var d1 = GetDoubleValue(values[0]);
var d2 = GetDoubleValue(values[1]);
return Compare(d1, d2);
}
/// <summary>
/// Overload in subclasses to create LesserThan, EqualTo, whatever.
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <returns></returns>
protected virtual bool Compare(double a, double b)
{
throw new NotImplementedException();
}
protected static double GetDoubleValue(Object o)
{
if (o == null || o == DependencyProperty.UnsetValue)
{
return 0;
}
else
{
try
{
return System.Convert.ToDouble(o);
}
catch (Exception)
{
return 0;
}
}
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
return this;
}
}
public class GreaterThan : ComparisonConverter
{
protected override bool Compare(double a, double b)
{
return a > b;
}
}
}
Themes\Generic.xaml
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>
<Style
xmlns:he="clr-namespace:HollowEarth"
TargetType="{x:Type he:SignalBars}"
>
<!-- Foreground is the bar borders and the fill for "active" bars -->
<Setter Property="Foreground" Value="Black" />
<Setter Property="InactiveBarFillBrush" Value="White" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Control">
<ControlTemplate.Resources>
<Style TargetType="Rectangle">
<Setter Property="Width" Value="4" />
<Setter Property="VerticalAlignment" Value="Bottom" />
<Setter Property="Stroke" Value="{Binding Foreground, RelativeSource={RelativeSource TemplatedParent}}" />
<Setter Property="StrokeThickness" Value="1" />
<Setter Property="Fill" Value="{Binding InactiveBarFillBrush, RelativeSource={RelativeSource TemplatedParent}}" />
<Setter Property="Margin" Value="0,0,1,0" />
<Style.Triggers>
<DataTrigger Value="True">
<DataTrigger.Binding>
<MultiBinding Converter="{he:GreaterThan}">
<MultiBinding.Bindings>
<Binding
Path="Value"
RelativeSource="{RelativeSource TemplatedParent}"
/>
<Binding
Path="Tag"
RelativeSource="{RelativeSource Self}"
/>
</MultiBinding.Bindings>
</MultiBinding>
</DataTrigger.Binding>
<Setter Property="Fill" Value="{Binding Foreground, RelativeSource={RelativeSource TemplatedParent}}" />
</DataTrigger>
</Style.Triggers>
</Style>
</ControlTemplate.Resources>
<ContentControl
ContentTemplate="{Binding ContentTemplate, RelativeSource={RelativeSource TemplatedParent}}">
<StackPanel
Orientation="Horizontal"
SnapsToDevicePixels="True"
UseLayoutRounding="True"
>
<!-- Set Tags to the minimum threshold value for turning the segment "on" -->
<!-- Remove one of these to make it four segments. To make them all equal height, remove Height here
and set a fixed height in the Rectangle Style above. -->
<Rectangle Height="4" Tag="0" />
<Rectangle Height="6" Tag="2" />
<Rectangle Height="8" Tag="4" />
<Rectangle Height="10" Tag="6" />
<Rectangle Height="12" Tag="8" />
</StackPanel>
</ContentControl>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ResourceDictionary>
Example XAML:
<StackPanel
xmlns:he="clr-namespace:HollowEarth"
Orientation="Vertical"
HorizontalAlignment="Left"
>
<Slider
Minimum="0"
Maximum="10"
x:Name="SignalSlider"
Width="200"
SmallChange="1"
LargeChange="4"
TickFrequency="1"
IsSnapToTickEnabled="True"
/>
<he:SignalBars
HorizontalAlignment="Left"
Value="{Binding Value, ElementName=SignalSlider}"
InactiveBarFillBrush="White"
Foreground="DarkRed"
/>
</StackPanel>

Usually you may need a ColorToBrushConverter, but not a BooleanToColor.
I would simply create different styles with triggers for each bar, like
<Style.Triggers>
<DataTrigger Binding="{Binding IsOffline}" Value="True">
<Setter Property="Background" Value="Salmon" />
</DataTrigger>
<DataTrigger Binding="{Binding IsPrinting}" Value="True">
<!--<Setter Property="Background" Value="Honeydew" />-->
<Setter Property="Background" Value="LightGreen" />
</DataTrigger>
</Style.Triggers>

Data trigger not firing off correct string value

So here's the idea.
If the textbox is empty, 'DataTrigger' should set the outline (BorderBrush) to red.
If the textbox is not empty / has text; then the dataTrigger should set the BorderBrush to Blue.
xmlns:conv="clr-namespace:WpfApplication1"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<!-- conv is referenced in the "clr-namespace:WpfApplication1" namespace. It's bassically a referal to a converter I'm using -->
<conv:IsNullConverter x:Key="isNullConverter"/>
<Style TargetType="{x:Type TextBox}">
<Style.Triggers>
<!-- if the textbox is empty, then the setter should set the border colour to red-->
<DataTrigger Binding="{Binding Words, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource isNullConverter}}" Value="True">
<Setter Property="BorderBrush" Value="Red"/>
</DataTrigger>
<!-- If it has text inside it, setter should set the border colour to blue -->
<DataTrigger Binding="{Binding Words, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource isNullConverter}}" Value="False">
<Setter Property="BorderBrush" Value="Blue"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid>
<TextBox x:Name="first" FontSize="14" TabIndex="1" Background="Black" BorderThickness="5" Foreground="White" Margin="29,10,132,272" />
</Grid>
Because it's not possible for datatriggers to see if a value is NOT null indipendently, I had to add some code to help it do that.
using System.Windows.Data;
using System.Globalization;
using System.ComponentModel;
namespace WpfApplication1
{
public class IsNullConverter : IValueConverter, INotifyPropertyChanged
{
// The string that the 'conv:' checks against
private string FOO;
// The DataTriggrer is bound to 'Words'
public string Words
{
get
{
return FOO;
}
set
{
if (FOO != value)
{
FOO = value;
RaisePropertyChanged("Words");
}
}
}
private void RaisePropertyChanged(string prop)
{
if (PropertyChanged == null)
{
PropertyChanged(this, new PropertyChangedEventArgs(prop));
}
}
public event PropertyChangedEventHandler PropertyChanged;
public string Error
{
get { return null; }
}
// This is the 'Convert' Parameter conv checks against. Here is the problem is
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
//This checks against the FOO string at the top of this class. Not the FOO in 'Words' get & set string
if (FOO == null)
{
value = true;
}
// So even if 'Words' raises the property changed, The origional FOO string remains unaffected.
// So the Datatrigger is never fired
if (FOO != null)
{
value = false;
}
return value;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new InvalidOperationException("IsNullConverter can only be used OneWay.");
}
}
}
The thing is if I append the string FOO like;
private string FOO = "Something";
The Datatrigger fires at runtime and changes the outline colour to blue.
But I need the colour to be based on the textbox content rather than what I directly declare the string as.
I tried binding the data Trigger to the 'Words' string but the outline colour remains red, empty or not.
And suggestions? I really don't mind if I have to completely throw this code upside down if there's a better way of doing it.

Here you go:
<TextBox x:Name="first" FontSize="14" TabIndex="1" Background="Black" BorderThickness="5" Foreground="White" Margin="29,10,132,272">
<TextBox.Style>
<Style TargetType="TextBox">
<Setter Property="BorderBrush" Value="Blue"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Text, RelativeSource={RelativeSource Self}}" Value="">
<Setter Property="BorderBrush" Value="Red"/>
</DataTrigger>
<DataTrigger Binding="{Binding Text, RelativeSource={RelativeSource Self}}" Value="{x:Null}">
<Setter Property="BorderBrush" Value="Red"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>

Bind to the TextBox.Text property by using RelativeSource:
<DataTrigger Binding="{Binding Text, RelativeSource={RelativeSource Self}, Converter={StaticResource isNullConverter}}" Value="True">
<!--apropriate setter-->
</DataTrigger>
This trigger sets the BorderBrush if Text is empty. To set the border brush when Text is not empty, just use normal Setter, without DataTrigger.
Also, note that within your ValueConverter you should use String.IsNullOrEmpty instead of plain NULL comparison.

You can simplify your converter to look something like
public class IsNullConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return String.IsNullOrEmpty((string) value);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new InvalidOperationException("IsNullConverter can only be used OneWay.");
}
}
and then in style bind TextBox.Text via converter
<Window.Resources>
<conv:IsNullConverter x:Key="isNullConverter"/>
<Style TargetType="{x:Type TextBox}">
<Setter Property="BorderBrush" Value="Blue"/>
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Text, Converter={StaticResource isNullConverter}}" Value="True">
<Setter Property="BorderBrush" Value="Red"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Window.Resources>
this will work but only if TextBox is not focused as then default template will take over and change BorderBrush. You can make it work but then you'll need to change default template as well where simpliest template would be another Setter in your Style
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBox}">
<Border
BorderBrush="{TemplateBinding BorderBrush}"
Background="{TemplateBinding Background}"
BorderThickness="{TemplateBinding BorderThickness}">
<ScrollViewer x:Name="PART_ContentHost"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>

Listbox groupstyle bind expander IsExpanded property

I have a list with users that are ordered in some groups.
This is my ListBox xaml :
<ListBox x:Name="UserContainer"
ItemsSource="{Binding allUserViewModel.UserView}"
Background="Transparent"
HorizontalContentAlignment="Stretch"
ScrollViewer.HorizontalScrollBarVisibility="Disabled"
ScrollViewer.VerticalScrollBarVisibility="Auto"
BorderThickness="0" Margin="0,0,0,7" Padding="0"
ItemContainerStyle="{DynamicResource ListBoxItemStyle}"
Visibility="{Binding allUserViewModel.UserView.Count, Converter={StaticResource ShowIfHasUsersConverter}}"
MouseEnter="UserContainer_OnMouseEnter" MouseLeave="UserContainer_OnMouseLeave">
<ListBox.Style>
<Style>
<Style.Triggers>
<Trigger Property="ListBox.IsGrouping" Value="true">
<Setter Property="ScrollViewer.CanContentScroll" Value="false" />
</Trigger>
</Style.Triggers>
</Style>
</ListBox.Style>
<ListBox.GroupStyle>
<GroupStyle>
<GroupStyle.ContainerStyle>
<Style TargetType="{x:Type GroupItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type GroupItem}">
<Expander IsExpanded="{Binding Path=Name.IsExpanded}" Style="{StaticResource EditedMetroExpander}" Padding="0,3,0,3">
<Expander.Header>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Left">
<TextBlock Text="{Binding Name}" Foreground="Silver"
FontSize="18" FontFamily="Segoe UI Light" VerticalAlignment="Center" />
</StackPanel>
</Expander.Header>
<ItemsPresenter />
</Expander>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</GroupStyle.ContainerStyle>
</GroupStyle>
</ListBox.GroupStyle>
<ListBox.Resources>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent" />
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black" />
<SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Color="Transparent" />
</ListBox.Resources>
<ListBox.ItemTemplate>
<DataTemplate>
<view:UserControlButton x:Name="UserControlButton" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
This is a list of users. Each user has a userviewmodel with a certain groupId to see in which group he should be.
So in my mainviewmodel which contains a list of those userviewmodels I set my groupdescriptions
public AllUserViewModel()
{
UserList = new ObservableCollection<UserViewModel>();
OnlineContacts = new List<UserViewModel>();
LocalContacts = new List<UserViewModel>();
UserView = (CollectionView)CollectionViewSource.GetDefaultView(UserList);
// Filter
if (UserView.CanFilter)
UserView.Filter = OnFilterUsers;
// Group
if (UserView.CanGroup && UserView.GroupDescriptions != null)
UserView.GroupDescriptions.Add(new PropertyGroupDescription(UserViewModel.GroupIdPropertyKey, new GroupDescriptionConverter()));
// Sorting
if (UserView.CanSort)
{
// Custom sort only available with ListCollectionView
ListCollectionView userListView = (ListCollectionView)CollectionViewSource.GetDefaultView(UserList);
userListView.CustomSort = new CustomUserComparer();
}
}
And this is my GroupDescriptionConverter
public class GroupDescriptionConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var groupId = (int)value;
var group = GroupController.Instance.GetGroup(groupId);
return group.Name;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
I want to bind the IsExpanded property on my expander on the ExpandGroup property of my group object.
public class Group
{
public int Id { get; set; }
public int OrderId { get; set; }
public string Name { get; set; }
public bool ExpandGroup { get; set; }
public bool NewLine { get; set; }
public Group()
{
}
}

A simple solution for this is to add a
private bool _isExpanded = true;
public bool IsExpanded
{
get { return _isExpanded; }
set { _isExpanded = value; }
}
property to your UserViewModel
and then do:
<Expander IsExpanded="{Binding Items[0].IsExpanded}">
on your template.
Simple and effective just like WPF should be

Enable/Disable Button, by rows in Grid

I have following code. Here listClear is an object, which is filled by ViewModel. I am using properties of this object to fill a Grid. In below code what property should I use to make Button disable in DataTrigger. I want Button to be disabled when Grid is empty, otherwise it should be enabled.
<Button Grid.Column="3" Margin="2" Command="{Binding Path=ClearCommand}" Content="Clear">
<Button.Style>
<Style TargetType="Button">
<Setter Property="IsEnabled" Value="True" />
<Style.Triggers>
<DataTrigger Binding="{Binding Path=listClear}" Value="">
<Setter Property="IsEnabled" Value="False"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>

You can use the List Count property for this to indicate empty
Example:
public partial class MainWindow : Window
{
private ObservableCollection<string> myVar = new ObservableCollection<string>();
public MainWindow()
{
InitializeComponent();
MyList.Add("test");
}
public ObservableCollection<string> MyList
{
get { return myVar; }
set { myVar = value; }
}
private void Button_Click(object sender, RoutedEventArgs e)
{
MyList.Clear();
}
}
Xaml:
<Window x:Class="WpfApplication11.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication11"
Title="MainWindow" Height="136.3" Width="208" x:Name="UI">
<Grid DataContext="{Binding ElementName=UI}">
<Button Content="Clear" Click="Button_Click">
<Button.Style>
<Style TargetType="Button">
<Setter Property="IsEnabled" Value="True" />
<Style.Triggers>
<DataTrigger Binding="{Binding Path=MyList.Count}" Value="0">
<Setter Property="IsEnabled" Value="False"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
</Grid>
</Window>
If your only using IEnumerable<T> its a bit more difficult because IEnumerable has no public properties to bint to, you would have to make a converter.
Something like this
public class IsEmptyConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is IEnumerable)
{
var enumerable = (IEnumerable)value;
foreach (var item in enumerable)
{
return false;
}
}
return true;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
Xaml:
<Window x:Class="WpfApplication11.MainWindow"
xmlns:local="clr-namespace:Namespace for converter"
....
....
<Window.Resources>
<local:IsEmptyConverter x:Key="IsEmptyConverter" />
</Window.Resources>
....
....
<DataTrigger Binding="{Binding Path=MyList, Converter={StaticResource IsEmptyConverter}}" Value="true">