WPF DataGrid with Entity Framework Core - Updating a row

It looks like there is something i don't understand with WPF Datagrid:

If i use DataGridTextColumn then it is working as expected. If i change a field and the to SaveChanges(); it will Save the changes as expected. But if i use DataGridTemplateColumn for the same field, in a TextBox, if i do SaveChanges(), it will not save. So what do i miss ? I've studied numerous tutorials but i can not find an answer. 

Deleting a row and inserting a row works always. I guess is because i populate the Datagrid using .ToObservableCollection();

So, i guess, my question is: How to SaveChanges() in DataGrid using Entity Framework Core ? 

I'm not expert in WPF. I'm trying to learn.

Thanks.