Binding to DependancyProperty - wpf

Question

My XAML won't bind and I can't see why
Using MVVM, I have the following code in my MyView.xaml
<Expander Header="{Binding ThresholdName}" IsExpanded="False" >
<properties:PropertiesVm Name="{Binding ThresholdName}" />
</Expander>
And this has a DataTemplate of MyViewModel.cs
As you can see, I'm using the ThresholdName twice. When I run my application, I can see the ThrehsoldName in the Header of the Expander indicating that the binding at this point is fine. The issue is binding to my "properties" object.
The Properties View is
<Grid>
<TextBlock Text="{Binding Name}" />
</Grid>
And the ViewModel(which inherits from DependancyObject) is
public static readonly DependencyProperty NameProperty = DependencyProperty.Register("Name", typeof(string), typeof(PropertiesVm));
public string Name
{
get { return (Convert.ToString(GetValue(NameProperty))); }
set { SetValue(NameProperty, value); }
}
The error message I get is
System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=Time; DataItem=null; target element is 'PropertiesVm' (HashCode=6494098); target property is 'Name' (type 'String')
And within my Dictionary, I have set the DataTemplate as
<DataTemplate DataType="{x:Type viewModel:PropertiesVm}">
<view:PropertiesView />
</DataTemplate>
This post suggests adding x:Name but that didn't help
Why does the property Name in my Properties ViewModel never get set? Or can I only do this with a UserControl, binding to code behind?

Answer 1

You've got things a bit about face.
Your Expander content needs to bind to a property of your top level view model which exposes your instance of PropertiesVm. A bit like:
public class TopLevelVm
{
public string ThresholdName { get; }
public PropertiesVm Properties { get; }
}
Then your XAML could be like:
<Expander Header="{Binding ThresholdName}" Content="{Binding }" />
Then the DataTemplate will pick the same DataContext, and your DataTemplate could look like this:
<Grid>
<TextBlock Text="{Binding ThresholdName}" />
<!-- Do something with .Properties -->
</Grid>