如何访问具有DataTemplate并分配了DataType的DataObject的DataTemplate？

I have a DataObject and a DataTemplate that has the DataType=x:Type DataObject. I have a ContentControl which has as Content the DataObject. On OnContentChanged() of that ContentControl I need to access smtg from the DataTemplate of the new Conten which is a DataObject.I have a DataObject and a DataTemplate that has