The property <property name> cannot be deleted because it is participating in the association <association name>
The selected property is set as the Association Property for the association between the classes indicated in the error message. Properties cannot be deleted if they are participating in an association between data classes.
Set the Association Property to a different property of the data class to enable successful deletion of the desired property.
To correct this error
Select the association line on the O/R Designer that connects the data classes indicated in the error message.
Double-click the line to open the Association Editor dialog box.
Remove the property from the Association Properties.
Try to delete the property again.