- In the navigation pane of App Studio, click Case types, and then click the case type that you want to open.
- On the Workflow tab, click a stage name.
- In the Stage property pane, click Validation.
- In the Attachments required for stage entry pane, click Add required attachment to display the list of attachment categories that your case type supports.
- Select an attachment category from the list.
- Click Save.
Caution: Your case needs to have at least one attachment in each of the required attachment categories, otherwise the application displays an error at run time.