As far as I know, you can't do this with autogenerated columns via xaml.
You have several options to do it:
- Iterate through the columns after the binding and set either the CellStyle or the CellTemplate.
- Create the columns in advance and then override the CellStyle or CellTemplate.
- Replace the data binding of each column with a new binding with a string format.
If I'll come up with another option I'll comment again.