Missing ValueMemberBinding In AutoComplete Box Class

In XAML, ValueMemberBinding can be defined like the following:
<input:AutoCompleteBox x:Name="a" Grid.Column="2" Grid.Row="4" Style="{StaticResource masterautocompleteStyle}"
SelectedItem="{Binding Path=item1}"
ValueMemberBinding="{Binding itemlist}" >

But in coding, I found that there is no such valuememberbinding. For example:
FactoryEdit = New FrameworkElementFactory(GetType(AutoCompleteBox))
FactoryEdit.SetBinding(AutoCompleteBox.???)
I cannot find ValueMemerBinding in the AutoCompleteBox class.