I need to access the container's DataContext from a UserControl (a grid containing textboxes and a listbox: I need to insert items in this list box) that I created in WPF: which is the best way to do it?
I was thinking to pass the DataContext as parameter to user control but think there is a cleaner way to do it.
Normally the
DataContext
will be inherited, just do not explicitly set it on theUserControl
and it will get it from its parent. If you have to set it you could still use theParent
property to get the parent, which you then can safe-cast to aFrameworkElement
and if it is not null you can grab itsDataContext
.H.B. answers the question in your title.
However the text poses a different design question. I'd ask you to reconsider your design.
A control inherits the DataContext property of its ancestor as long as no one in between explicitly overrides.
If the user control needs data, it should get it from its data source (a viewmodel for the user control). So in this case, the user control can obtain the data it needs from the
ListItemsForDisplay
property exposed on theSomeViewModel
instance. No need to get parent and cast.. much cleaner.Add this BindingProxy class to your project:
Data="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}},Path=DataContext}"
If you needed something more complex you could use a custom converter.Now you have access to that parent's DataContext:
{Binding Data.MyCommand, Source={StaticResource BindingProxy}}
I sometimes have nested User controls and a grandchild usercontrol sometimes needs the grandparent's view's data context. The easiest way I have found so far (and I'm somewhat of a newbie) is to use the following:
I wrote up a more detailed example on my blog if you want more specifics.