Changes API: How to Subscribe to Document Changes

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Subscribe to document changes using ForDocument, ForDocumentsInCollection, ForDocumentsStartingWith, or ForAllDocuments.

The Subscribe method on the observable these methods return accepts only an IObserver object by default.
To instead subscribe with a delegate, like the change => ... lambda used in the examples below, add the System.Reactive package to your project.
This adds Subscribe overloads that take delegates, including ones with error and completion handlers.

• In this article:
  • ForDocument
  • ForDocumentsInCollection
  • ForDocumentsStartingWith
  • ForAllDocuments
  • DocumentChange and DocumentChangeTypes syntax

ForDocument

Single document changes can be observed using ForDocument method.

Syntax

IChangesObservable<DocumentChange> ForDocument(string docId);

Parameters
docId	string	ID of a document for which notifications will be processed.

Return Value
IChangesObservable<DocumentChange>	Observable that allows to add subscriptions to notifications for given document.

Example

IDisposable subscription = store
    .Changes()
    .ForDocument("employees/1")
    .Subscribe(
        change =>
        {
            switch (change.Type)
            {
                case DocumentChangeTypes.Put:
                    // do something
                    break;
                case DocumentChangeTypes.Delete:
                    // do something
                    break;
            }
        });

ForDocumentsInCollection

To observe all document changes in particular collection use ForDocumentInCollection method. This method filters documents by @collection metadata property value.

Syntax

IChangesObservable<DocumentChange> ForDocumentsInCollection(string collectionName);

IChangesObservable<DocumentChange> ForDocumentsInCollection<TEntity>();

Parameters
collectionName	string	Name of document collection for which notifications will be processed.

Return Value
IChangesObservable<DocumentChange>	Observable that allows to add subscriptions to notifications for given document collection name.

Overload with TEntity type uses Conventions.GetCollectionName to get collection name.

Example

IDisposable subscription = store
    .Changes()
    .ForDocumentsInCollection<Employee>()
    .Subscribe(change => Console.WriteLine("{0} on document {1}", change.Type, change.Id));

or

string collectionName = store.Conventions.FindCollectionName(typeof(Employee));
IDisposable subscription = store
    .Changes()
    .ForDocumentsInCollection(collectionName)
    .Subscribe(change => Console.WriteLine("{0} on document {1}", change.Type, change.Id));

ForDocumentsStartingWith

To observe all document changes for documents with ID that contains given prefix use ForDocumentsStartingWith method.

Syntax

IChangesObservable<DocumentChange> ForDocumentsStartingWith(string docIdPrefix);

Parameters
docIdPrefix	string	Document ID prefix for which notifications will be processed.

Return Value
IChangesObservable<DocumentChange>	Observable that allows to add subscriptions to notifications for given document ID prefix.

Example

IDisposable subscription = store
    .Changes()
    .ForDocumentsStartingWith("employees/1") // employees/1, employees/10, employees/11, etc.
    .Subscribe(change => Console.WriteLine("{0} on document {1}", change.Type, change.Id));

ForAllDocuments

To observe all document changes use ForAllDocuments method.

Syntax

IChangesObservable<DocumentChange> ForAllDocuments();

Return Value
IChangesObservable<DocumentChange>	Observable that allows to add subscriptions to notifications for all documents.

Example

IDisposable subscription = store
    .Changes()
    .ForAllDocuments() // employees/1, orders/1, customers/1, etc.
    .Subscribe(change => Console.WriteLine("{0} on document {1}", change.Type, change.Id));

DocumentChange and DocumentChangeTypes syntax

• DocumentChange
• DocumentChangeTypes

The notification object delivered to subscribers when a document changes.

class DocumentChange
{
    DocumentChangeTypes Type
    string Id
    string CollectionName
    string ChangeVector
}

Property	Type	Description
Type	DocumentChangeTypes	Document change type enum
Id	string	Document identifier
CollectionName	string	Document's collection name
ChangeVector	string	Document's ChangeVector

enum DocumentChangeTypes
{
    None,
    Put,
    Delete,
    BulkInsertStarted,
    BulkInsertEnded,
    BulkInsertError,
    DeleteOnTombstoneReplication,
    Conflict,
    Common,
}

Name	Value
None	0
Put	1
Delete	2
BulkInsertStarted	4
BulkInsertEnded	8
BulkInsertError	16
DeleteOnTombstoneReplication	32
Conflict	64
Common	Put | Delete