This is an example of the Expression Editor from WPF I just got some great news after testing current beta bits of the Pivot Grid controls across all versions use much less memory (can be up to 4 time less depending on data type) for Unbound Field Values.
This is great news for users who are using the Unbound Field feature of the pivot grid. If you have not worked with Unbound Fields they can be quite handy for displaying data that is not in your source data. To use the feature all you need to do is mark a pivot field’s UnboundType property to an appropriate UnboundColumnType and then you can either set it's UnboundExpression property or for event more flexibility you can handle the CustomUnboundFieldData event. When the event is fired you can do any type of logic you would like to populate the unbound fields. To give you context for the field the CustomUnboundFieldData event receives CustomFieldDataEventArgs which contains information on the current field, the current row's index in the data source and the Value property that you will need to populate.
There is a nice demo of this feature for ASP.NET called Data Shaping Features - Unbound Fields the basic steeps used in this demo are the same across all versions of the pivot grid.
We hope you will enjoy this increase in performance and maybe play with a unused feature.