Changes API

The RavenDB client offers a push notification feature that allows you to receive messages from a server about events that occurred there. You are able to subscribe to events for all documents, indexes, and operations as well as to indicate a particular one that you are interested in. This mechanism lets you notify users if something has changed without the need to do any expensive polling.

Accessing Changes API

The changes subscription is accessible by a document store through its IDatabaseChanges interface.

IDatabaseChanges Changes(string database = null);

Connection interface

IDatabaseChanges inherits from IConnectableChanges<TChanges> interface that represent the connection.

public interface IConnectableChanges<TChanges> : IDisposable
    where TChanges : IDatabaseChanges
{
    // returns state of the connection
    bool Connected { get; }

    // A task that ensures that the connection to the server was established.
    Task<TChanges> EnsureConnectedNow();

    //An event handler to detect changed to the connection status
    event EventHandler ConnectionStatusChanged;

    //An action to take if an error occured in the connection to the server
    event Action<Exception> OnError;
}

Subscriptions

In order to retrieve notifications you have to subscribe to server-side events by using one of the following methods:

• ForAllDocuments
• ForAllCounters
• ForAllIndexes
• ForAllOperations
• ForDocument
• ForDocumentsInCollection
• ForDocumentsStartingWith
• ForCounter
• ForCounterOfDocument
• ForCountersOfDocument
• ForIndex
• ForOperationId

Unsubscribing

In order to end subscription (stop listening for particular notifications) you must Dispose it.

IDatabaseChanges subscription = store.Changes();
await subscription.EnsureConnectedNow();
subscription.ForAllDocuments().Subscribe(change => Console.WriteLine("{0} on document {1}", change.Type, change.Id));

try
{
    // application code here
}
finally
{
    if (subscription != null)
        subscription.Dispose();
}

Remarks