Client tracking

Applies To: yes OData Client V7

OData Client for .NET supports two levels tracking : entity tracking and property tracking(only top level properties). Entity tracking enables you to track an entity in DataServiceContext. You can enable property tracking by aid of DataServiceCollectionOfT.

Entity Tracking

DataServiceContext provides several ways to track an entity.

  1. Newly added entities will be automatically tracked.
  2. If you use DataServiceContext.AttachTo to attach an entity, DataServiceContext will track the entity.
  3. Entities returned by queries are also tracked if DataServiceContext.MergeOption is not MergeOption.NoTracking.

Once entities are tracked, you can use DataServiceContext.EntityTracker to get each entity descriptor which is used to describe the entity on client side. the entity tracker can also be used to get the link descriptor of all tracked links.

Once entities are tracked, the changes of these entities can be sent back to the data service when you call DataServiceContext.SaveChanges method.

If you are using MergeOption.NoTracking when you query an entity. You cannot get ETag of the entity from DataServiceContext if it exists, since you cannot get the entity descriptor for the entity. Then, if you want to call AttachTo to track the entity, you need provide the ETag of the entity.

DataServiceContext tracks each relationship as a link. You can use methods AddRelatedObject, AttachLink, AddLink, SetLink, DetachLink, DeleteLink to track a link.

One sample to use AttachTo and DeleteLink.

	DefaultContainer dsc = new DefaultContainer(new Uri(""));

    public void ClientEntityTracking()
        var person = new Person()
	        UserName = "clydeguess"
	    var oneFriend = new Person()
	        UserName = "keithpinckney"
	    dsc.AttachTo("People", person);
	    dsc.AttachTo("People", oneFriend);
	    dsc.DeleteLink(person, "Friends", oneFriend);

Property Tracking

Please refer to client property tracking for patch for detail.