An external data property is used to reference a file stored on the client device’s file system. This file is external to the application’s production data. The file data itself is not stored with the production data. This property type is normally used in conjunction with the file transfer functionality. The default display value of an external data property is the full path and file name of the referenced file.
For object properties the attributes of this property type related to the location for the file specify where the file will be stored on the client device when retrieved from the back end system. For transaction properties these same attributes specify the default location from which the user should make a selection. The file dialog opened in this case does allow the user to navigate the file system to select the desired file. Two separate paths can be defined for the external data property, one for client devices running the Windows PC group of operating systems, and a second for client devices running supported versions of the Mobile Windows OS’s.
The attributes of this data type also allow for designating whether the file should be read-only on the client device, the file extension for the file, and whether or not to delete the file when the parent object to the property is deleted.
The recommended use for this property type is define an object that represents the document and includes this property, as well as other information about the file. The external data property itself will reference the location of the file and can return the file’s full path and name, just the file name, just the file path, just the file extension, as well as metadata about the file such as its last modified date and time and whether or not it has been modified since it was downloaded to the client device. Many of these values are exposed via rules and/or format strings. A separate property of a data type other than external data must exist and be referenced by the external data property that contains the name the file will be given when saved on the client device. This value must be set during synchronization prior to transferring the file itself.