Question

I like design time data, especially when creating small widgets. For this very simple use case I’m having trouble binding to the properties of a design-time list which I have created in xaml.

Please find my ViewModel, View and SampleData below;

ViewModel

internal class SummaryViewModel : ViewModelBase
{
    public string Title { get; set; }

    public IList<Person> PersonList { get; set; }

    internal SummaryViewModel()
    {
        PersonList = new List<Person>();
    }
}

Sample Data

<ViewModel:SummaryViewModel xmlns:ViewModel="ViewModel" Title="Test Title">
    <ViewModel:SummaryViewModel.Connections>
        <ViewModel:ConnectionViewModel Id="0" />
        <ViewModel:ConnectionViewModel Id="1" />
    </ViewModel:SummaryViewModel.Connections> 
</ViewModel:SummaryViewModel>

View

<StackPanel x:Class="View.SummaryView"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
            xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 

            mc:Ignorable="d" 
            d:DesignHeight="100" 
            d:DesignWidth="100"
            d:DataContext="{d:DesignData Source=/DesignData/SampleSummaryViewModel.xaml}"

            Orientation="Vertical"
            Background="LightGreen">

    <!-- This Works -->
    <Label FontSize="10" FontWeight="Bold" Content="{Binding Title}" />

    <!-- This Works -->
    <ListBox ItemsSource="{Binding PersonList}" />

    <!-- This DOESN'T work -->
    <Label FontSize="8" Content="{Binding PersonList, Path=Count}"/>
</StackPanel>

How would you configure SampleData such that you could bind to the Count of a list specified therein?

I have tried setting the resource type as both DesignData and DesignDataWithDesignTimeCreatableTypes with no luck.

Answer 1

It should be:

<Label FontSize="8" Content="{Binding Path=PersonList.Count}"/>

Also Mårten is correct, you should use an ObservableCollection instead.

HTH