Entity toEntity = new Entity("activityparty");
toEntity.Attributes.Add("partyid", new EntityReference(ToEntityName, ToId));
Entity fromEntity = new Entity("activityparty");
fromEntity.Attributes.Add("partyid", new EntityReference(FromEntityName, FromId));
letter["from"] = new Entity[] { fromEntity };
letter["to"] = new Entity[] { toEntity };
类似以上.