What does DataContext="{Binding}" mean?

Question

I'm trying to find out where the items in a HeaderedContentControl come from in a project that's not mine. Here's the code:

        <HeaderedContentControl              Content="{Binding Path=Workspaces}"             ContentTemplate="{StaticResource WorkspacesTemplate}"             Header="Workspaces"             Style="{StaticResource MainHCCStyle}"              DataContext="{Binding}" // <--- this         />  <DataTemplate x:Key="WorkspacesTemplate"> <TabControl    IsSynchronizedWithCurrentItem="True"    ItemsSource="{Binding}"    ItemTemplate="{StaticResource ClosableTabItemTemplate}"   Margin="4"   /> 

so let's examine it:

1. ContentTemplate attribute describes how the items are desplayed.
2. WorkspacesTemplate sets ItemsSource's attribute to {Binding} meaning it's bound to its DataContext property (DataContext of HeaderedContentControl)
3. So I look at HeaderedContentControl's dataContext, but it is described as "{Binding}" as well...

What does that mean?

Answer 1

Without seeing more of your code it is hard to be certain, but DataContext="{Binding}" is quite often unnecessary, as any object in the current binding context will automatically have its DataContext property set to the equivalent of {Binding}.

Remember:

• Property="{Binding}" means "set this.Property to the evaluated value of this.DataContext"
• Property="{Binding Path=SubProperty}" means "set this.Property to the evaluated value of this.DataContext.SubProperty"
• etc

This means that DataContext="{Binding}" means "set this.DataContext to the evaluated value of this.DataContext", which (in most cases) is redundant!

Answer 2

{Binding} is something like bind 'this' or current data context - assigned or inherited from parents. For better understanding, equivalent for {Binding} is {Binding .} or {Binding Path=.}