This property allows a client program, in an AssociationRequest event, to select which transfer syntax to accept for a given presentation context, the list offered being found in the OfferedTS property.  If none of the offered contexts is acceptable, then instead of setting this value, the Reject method should be called.
If no value is set, and Reject is not called, then DicomObjects will automatically select a value, based on the registry settings.

On an established association, whether incoming or outgoing, the client may use this property to check which transfer syntax will be used, especially if the same abstract context exists in more than one presentation context.  The DicomConnection’s PreferredPCID property may then be set to the appropriate DicomContext’s ContextID value.

DicomContext Object  | DicomContext Members