WPF Update DataGrid/ListBox GroupItem Text

I have a DataGrid/ListBox grouped by ListCollectionView. I have set a control template for GroupItem too. Everything works great.

I show sum of a column in the GroupItem using a converter class i wrote. The problem is that when i edit a开发者_Python百科 cell value, the GroupItem text is not updated.

I appreciate your helps :)

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Does your data object implement INotifyPropertyChanged so that the UI is notified properly when the underlying data is changed?