[Member name] Snapshot [Description] 
Volatile data can be read. Before a transaction modifies data, it verifies if another transaction has changed the data after it was initially read. If the data has been updated, an error is raised. This allows a transaction to get to the previously committed value of the data. When you try to promote a transaction that was created with this isolation level, an InvalidOperationException is thrown with the error message "Transactions with IsolationLevel Snapshot cannot be promoted".