Design time data for datatemplate in xaml

Question

This may be a stupid question, but is it possible to define some sample data as DataContext in order to see my DataTemplate in DesignView?

At the moment I always have to run my application to see whether my changes are working.

E.g. with the following code DesignView just shows an empty list box:

 <ListBox x:Name="standardLayoutListBox" ItemsSource="{Binding myListboxItems}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <Label Grid.Column="0" Content="{Binding text1}" />
                <Label Grid.Column="1" Content="{Binding text2}" />
            </Grid>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

Gid

Please see the solutions presented in this post: #1890466 – Exchequer

I read many samples for this by now, but I'm really not able to get this simple Listbox be filled at design time. I'm sure I'm missing something, but I can't find out what. Is it possible for you to provide a working sample for my listbox? – Gid

See my answer below for the sample code. – Exchequer

I have it running now, but I don't know why:-( For those interested, this sample helped a great deal: st-lange.net/post/… – Gid

Answer 1

public class MyMockClass
{
    public MyMockClass()
    {
        MyListBoxItems.Add(new MyDataClass() { text1 = "test text 1", text2 = "test text 2" });
        MyListBoxItems.Add(new MyDataClass() { text1 = "test text 3", text2 = "test text 4" });
    }
    public ObservableCollection<MyDataClass> MyListBoxItems { get; set; }
}

public class MyDataClass
{
    public string text1 { get; set; }
    public string text2 { get; set; }
}

In Your XAML

Add the namespace declaration

 xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

Add the mock data context to window/control resources

<UserControl.Resources> 
    <local:MyMockClass x:Key="DesignViewModel"/> 
</UserControl.Resources>

Then Modify Your ListBox to Reference the design time object

<ListBox x:Name="standardLayoutListBox" 
 d:DataContext="{Binding Source={StaticResource DesignViewModel}}"
ItemsSource="{Binding MyListBoxItems}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <Label Grid.Column="0" Content="{Binding text1}" />
                <Label Grid.Column="1" Content="{Binding text2}" />
            </Grid>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

Exchequer

After adding myListBoxItems = new ObservableCollection<MyDataClass>(); to the constructor of MyMockClass there is no error message, but Listbox is nonetheless empty. – Gid

I can't see any other problems. If you are really serious about wanting design time data, I would recommend that you look into MEF concepts. I use Cinch (Search for "ViewModel Design" to see some design time support). Sorry I can't help with a simpler solution. – Exchequer

Don't forget to set mc:Ignorable in the namespace declarations: xmlns:mc="schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" – Crabber

This solution appears to work for homogenous lists where the data template is attached directly to the 'ItemTemplate' property. However, there doesn't seem to be a solution for pure MVVM solutions where you want the items control to pick up any DataTemplate found in the resources that can be associated with a view model. – Cart

The local resource definition can be excluded if the design DataContext references the type like this: d:DataContext="{d:DesignInstance IsDesignTimeCreatable=True, Type=local:MyMockData}" – Monstrosity

@DaveAndersen (or others): With either approach, I get the error: "Object reference not set to an instance of an object." The underlined error is either the tag <local:MyMockClass ... /> or the parameter d:DataContext ... local:MyMockClass}". In either case, MyMockClass shows up in the Intellisense box when I type local:. Thoughts? – July

@Steven, is your mock class marked as public? That's all I can think of off the top of my head. – Monstrosity

@DaveAndersen It is public. I created a separate question for this issue. See: #45990657 – July

Answer 2

Wen you are in the designer you should not have to mess with the view models therefore I think it's bet to include design time data in xaml and not in c#, have a look at this simple POCO representation

<ListView ItemsSource="{Binding Items}">
        <d:ListView.ItemsSource>
            <x:Array Type="{x:Type models:Monkey}">
                <models:Monkey Name="Baboon" Location="Africa and Asia"/>
                <models:Monkey Name="Capuchin Monkey" Location="Central and South America"/>
                <models:Monkey Name="Blue Monkey" Location="Central and East Africa"/>
            </x:Array>
        </d:ListView.ItemsSource>
        <ListView.ItemTemplate>
            <DataTemplate x:DataType="models:Monkey">
                <TextCell Text="{Binding Name}"
                          Detail="{Binding Location}" />
            </DataTemplate>
        </ListView.ItemTemplate>

Huguenot