Working with "custom" XML

The Engine supports the association of arbitrary XML with each event in a DCR graph. This feature is used extensively by the DCR Solutions Portal, Designer, and Active Repository offerings. This document describes how to work with custom XML in event definitions.

Retrieving custom XML

Custom XML lives inside the Marking of an event. Suppose we want to retrive the custom XML of an event Activity2 in graph graph:

  Path eid = new Path ("Activity2");      // Construct a path for the event
  Marking m = graph.GetMarking(eid);      // Retrieve the marking of the event
  XElement xelem = m.Custom;              // Retrieve the custom XML from the marking

It may be convenient to do to these operations in one line, as is done in the Samples project:

  XElement xelem = graph.GetMarking(new Path("Activity2")).Custom;

Writing custom XML

To write custom XML, replace it in its entirety in the marking. Remember to write back the updated marking to the graph. Assume we have suitable XML in a variable custom of type XElement.

  Path eid = new Path ("Activity2");      // Construct a path for the event
  Marking m = graph.GetMarking(eid);      // Retrieve the marking of the event
  m.Custom = custom;                      // Set custom XML in marking
  graph.SetMarking(eid, m);               // Set marking of event

Writing custom XML when constructing events

To set custom XML in events constructed using [AddEvent](xref:M:DCR.Graph.AddEvent(DCR.Path,DCR.Marking) and variants, one may first construct the event, then use the pattern of the preceding section to update the XML. However, custom XML can also be set directly when constructing a Marking. Here is how to construct an event at the root with id A, label Authorised payout, and custom XML as specified in the variable custom of type XElement:

  XElement custom = ...;

  graph.AddEvent(new Path("A"), new Marking("Authorised payout", custom));

See the Marking constructor.