Expression Blend binding list doesn't list interface properties for binding.

Question

Made a much simpler example, hopefully someone can follow this and help me

Here is my code.

ViewModel

public class ViewModel
{
    private Person _noninterfacePerson;
    private IPerson _interfacePerson;

    public ViewModel()
    {
        _noninterfacePerson = new Person();
        _interfacePerson = new Person();
    }

    public Person NonInterfacePerson
    {
        get { return _noninterfacePerson; }
    }

    public IPerson InterfacePerson
    {
        get { return InterfacePerson; }
    }

}

Person

public class Person : IPerson
{
    public Person()
    {

    }

    public string Name
    {
        get;
        set;
    }

    public int age
    {
        get;
        set;
    }

}

IPerson

public interface IPerson
{
    int age { get; set; }
    string Name { get; set; }
}

View

<Window x:Class="WpfApplication2.MainWindow"
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication2"
        mc:Ignorable="d"
 Title="MainWindow" Height="350" Width="525">
 <Grid d:DataContext="{d:DesignInstance local:ViewModel}">

 </Grid>
</Window>

In Expression Blend if I insert a textblock, click on the "Advanced Options" -> Data Binding... -> Data Context I see both InterfacePerson and NonInterfacePerson as options to bind to. However, NonInterfacePerson has a little arrow showing the other properties I can bind to. Age and Name in this case.

The same thing happens when I set d:DataContext to a d:DesignData Source. I didn't use that for this example because it is more complicated. But that is where I really want this to work because then I can see all my binding options AND have sample data.

If I instead do this in my view:

<Window x:Class="WpfApplication2.MainWindow"
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication2"
        mc:Ignorable="d"
 Title="MainWindow" Height="350" Width="525">
 <Window.Resources>
 <local:ViewModel x:Key="DummyVM"/>
 </Window.Resources>
 <Grid d:DataContext="{Binding Source={StaticResource DummyVM}}">

 </Grid>
</Window>

Then I CAN see the properties of InterfacePerson, however, I still cant get the easy implementation of sample data that I would like using d:DesignData.

It should be noted that in all cases, if I manually type in the path it works fine. This is purely a matter of getting Blend to show them so it is easier to set up the bindings.

Thanks for any help you can provide on this!

Answer 1

I am pretty sure they use reflection to identify the properties of an object and an Interface is only a description of layout, not a real object, so has no reflected properties.

Hope this helps.