Called by Lightstreamer Kernel through the Remote Server to know whether the Data Adapter, after a subscription for an Item, will send some Snapshot Item Events before sending the updates. An Item Snapshot can be represented by zero, one or more Item Events, also depending on the Item type. The decision whether to supply or not to supply Snapshot information is entirely up to the Data Adapter. 

The method should be nonblocking. The availability of the snapshot for an Item should be a known architectural property. When the snapshot, though expected, cannot be obtained at subscription time, then it can only be considered as empty. 

bool IsSnapshotAvailable(string itemName);

bool IsSnapshotAvailable(string itemName);

Function IsSnapshotAvailable(itemName As string) As bool