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You can bind to the navigation property of entity framework. Use an observable collection for the Company combobox and bind the employee combobox to the navigation property. So in ViewModel you only need: <pre><code>Public Property Companies As ObservableCollection(Of Company) Public Property SelectedCompany As Company Public Property SelectedEmployee As Employee </code></pre> Lets say that your entity framework has a navigation property on your comapny entity named company_employee. You can bind directly to that in your view like: <pre><code><ComboBox ItemsSource="{Binding SelectedCompany.company_employee}" SelectedItem="{Binding Path=SelectedEmployee,Mode=TwoWay}" /> </code></pre> WPF and entity framework will get the required data for you. and it will only be the employees that have the matching company. WHat I do is use a usercontrol as my view and have a grid/usercontrol/contentcontrol that would bind (set its datacontext) to the SelectedCompany in side my View. ie <pre><code><ContentControl Name="DetailControl" DataContext="{Binding Path=SelectedCompany, Mode=TwoWay}" > </code></pre> Then within that contentcontrol the binding for a combox or datagrid or listview is as follows if you still want to have a selectedemployee binding: <pre><code><ComboBox ItemsSource="{Binding company_employee}" SelectedValue="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}},Path=DataContext.SelectedEmployee}" /> </code></pre> But if you don't need the selectedEMployee you can just bind to the EMployeeID in the company Table as follows: <pre><code><ComboBox ItemsSource="{Binding company_employee}" SelectedValue="{Binding EmplyeeID, Mode=TwoWay" /> </code></pre> You just bind directely to the navigation property and use the employee Foreign key. I just typed these out so you might need to double check all the names etc.. Hope these options help EDIT 1: Include example (in vb.net) <pre><code> Dim MyQuery As IQueryable(Of Company) = CType((From MyResults In Context.Company.Include("Employee") Select MyResults), IQueryable(Of Company)) </code></pre> see: <a href="http://msdn.microsoft.com/en-us/library/gg696450%28v=vs.103%29.aspx" rel="nofollow">Include Method MSDN Documentation</a>
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1. POWPF MVVM master-detail collections with Entity Framework
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1. USJ King
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1. COOk. Is this efficient, I mean the database is not hit every time the SelectedCompany is changed, assuming the corresponding Employees data has been already loaded once? (I can't unfortunately profile the database queries here)
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2. COi quess it depends on why you don't want a db hit. If you have 1000 records and your user only interacts with a couple of them, then your db only gets hit a couple of times, but if you want to load the navigation properties at initial query, you can do that using the include method. See edited answer for include option.
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Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.