System.Collections.ObjectModel is included. Visual studio 2012 still says Type or namespace name 'ObservableCollection' could not be found.
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Code:
class ObservableClass : ObservableCollection<OtherClass>
{
}
EDIT: This is .NET Framework 3.5 and is a console application
You’re probably missing an assembly reference… depending on which framework you are targeting, this class might be found: