ReadOnly property cause wrong update

I’m using Gridview with AccessDataSource control. I have enable edit button to change  all the field value. In this condition all work fine.< xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Than I need to avoid that some fields can be editate so I have set the ReadOnly property for this filed to True.

In this condition when I select Upgrade the value of the fields with ReadOnly property set True are replaced whit empty value.

Why this happen

Many thanks for your support. Best Regards. Riccardo.