General Actions:
Last modified on January 25, 2013 16:21
DevForce’s client-side cache enables applications to operate in a partially connected or fully disconnected environment. You can query, modify, and even create new entities while offline, and you can save the cache to the file system to preserve the state of the entities if the application or computer needs to be shut down.
Query entities offline
With a few small exceptions, the same LINQ queries you execute while connected will work disconnected, except that they will be fulfilled entirely from the client-side cache. While disconnected, the EntityManager will use a QueryStrategy of CacheOnly for all queries since the EntityServer is not available. (To learn more about QueryStrategies, see Control query execution.)
Create, modify, and delete entities offline
Creating and modifying entities is not affected by being disconnected, as these are purely client-side operations until they are committed to the server by SaveChanges or SaveChangesAsync. Similarly, you can mark the deletion of an entity while disconnected, and the EntityState will change to Deleted, but the entity will not be committed until the save.
Connect and Disconnect
By default a new EntityManager will connect to the EntityServer. If you wish to create a new disconnected EntityManager, then pass a value of false for the shouldConnect parameter in the constructor. The signature for this constructor is shown below, but you can learn more about this in Create an offline EntityManager.
| C# | public EntityManager(bool shouldConnect = true, String dataSourceExtension = null, EntityServiceOption entityServiceOption = EntityServiceOption.UseDefaultService, String compositionContextName = null) |
You can tell the EntityManager to enter the disconnected state by calling the Disconnect method. When network access is restored, you can reconnect by calling Connect or ConnectAsync. While disconnected, the IsConnected property will return false.
If the EntityManager is in the connected state and it experiences a loss of connection, it will:
- Enter into the disconnected state.
- Raise the EntityServerError event with an EntityServerConnectionException in the EntityServerErrorEventArgs, which you should handle and indicate to the user.
- Throw an EntityServerConnectionException if the EntityServerErrorEventArgs was not marked as handled in the EntityServerError event.
When creating a new EntityManager while offline, you should pass false for the shouldConnect parameter. This will keep the EntityManager from automatically attempting to establish a connection to the entityserver.