WPF - ItemsControl 中的条件绑定

Question

I'm very new to WPF, and am just getting started with data binding. What I'd like to do is generate a list of checkboxes based on a list in my view model. The XAML I have at the moment is:

<ItemsControl ItemsSource="{Binding Path=TestList, UpdateSourceTrigger=PropertyChanged}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <StackPanel Orientation="Vertical" />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <CheckBox Content="{Binding Path=Name}" IsChecked="{Binding Path=Enabled, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Margin="10,5,10,5" />
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

This works correctly, and generates a checkbox for every item in TestList . What I'd like to do is only generate checkboxes for items where the condition TestList[i].Type == "Mode" is true. I believe that I may need to use a <DataTrigger> element, but I don't know the details of how to do this.

[EDIT] Just to clarify, each element of TestList has Name , Enabled , and Type properties.

Answer 1

There are several ways to do this. However, the simplest static approach would be to just filter it at your ViewModel

Filtered = new ObservableCollection(TestList.Where(x => x.Type == "Mode"));

...

<ItemsControl ItemsSource="{Binding Path=Filtered , UpdateSourceTrigger=PropertyChanged}">

_{Note : There are fancier more dynamic ways to achieve this, though this might help you out}

Answer 2

As I guess that you want to make the checkbox appear if TestList.Type changes, I would suggest make a Converter and Bind it to the CheckBox Visibility.

public sealed class CheckBoxVisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value == null || parameter == null)
            return Visibility.Visible;

        var type = (string)value;
        var condition  = (string)parameter;
        return type.Equals(condition) ? Visibility.Visible : Visibility.Collapsed;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value;
    }
}

And then in the dictionary add the reference to your namespace

xmlns:converters="clr-namespace:Projct.Converters;

and in the resources dictionary

 <converters:CheckBoxVisibilityConverter x:Key="CheckBoxConverter"/>

Finally in the xaml

<ItemsControl.ItemTemplate>
    <DataTemplate>
        <CheckBox
            Margin="10,5,10,5"
            Content="{Binding Path=Name}"
            IsChecked="{Binding Path=Enabled, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
            Visibility="{Binding Path=Type, Converter={StaticResource CheckBoxConverter}, ConverterParameter=Mode}" />    
    </DataTemplate>
</ItemsControl.ItemTemplate>