void ITransactedModelEvent.Rollback(ModelTransaction transaction)
{
Prepare(transaction);
ModelEventScope.Perform(() =>
{
ModelContext context = Instance.Type.Context;
ModelInstanceList list = Instance.GetList(Property);
if (Added != null)
{
foreach (ModelInstance item in Added)
{
list.Remove(item);
}
}
if (Removed != null)
{
foreach (ModelInstance item in Removed)
{
list.Add(item);
}
}
});
}
/// <summary>
/// Combines two or more transactions creating a new transaction.
/// </summary>
/// <param name="transactions"></param>
/// <returns></returns>
public static ModelTransaction Combine(IEnumerable <ModelTransaction> transactions)
{
// Get the first transaction
ModelTransaction first = transactions.FirstOrDefault();
if (first == null)
{
return(null);
}
// Verify that all transactions are tied to the same context
if (transactions.Skip(1).Any(t => t.Context != first.Context))
{
throw new InvalidOperationException("Cannot combine ModelTransactions that are associated with different ModelContexts");
}
// Verify than none of the transactions are still active
if (transactions.Any(t => t.IsActive))
{
throw new InvalidOperationException("Cannot combine ModelTransactions that are still active");
}
// Create a new transaction and combine the information from the specified transactions
// Return the combined transactions
var newTransaction = new ModelTransaction();
foreach (var transaction in transactions)
{
// Copy new instances
if (transaction.newInstances != null)
{
if (newTransaction.newInstances == null)
{
newTransaction.newInstances = new Dictionary <string, ModelInstance>();
}
foreach (var entry in transaction.newInstances)
{
newTransaction.newInstances.Add(entry.Key, entry.Value);
}
}
// Copy events
foreach (var evt in transaction.events)
{
newTransaction.events.AddLast(evt);
}
}
return(newTransaction);
}
/// <summary>
/// Performs a set of previous changes, performs the specified operation, and records new changes that
/// occur as a result of the previous changes and the specified operation.
/// </summary>
/// <param name="operation"></param>
/// <param name="transaction"></param>
/// <returns></returns>
public ModelTransaction Perform(Action operation, ModelTransaction transaction)
{
// Create an event scope to track changes that occur as a result of applying previous changes
ModelEventScope eventScope = new ModelEventScope();
try
{
// Perform previous changes
Perform();
// Return the new changes that occurred while applying the previous changes
return(Chain(transaction).Record(() =>
{
// Allow model subscribers to be notified of the previous changes
eventScope.Exit();
// Clear the reference to the event scope to ensure it is not disposed twice
eventScope = null;
// Perform the specified operation
if (operation != null)
{
operation();
}
}));
}
catch (Exception actionException)
{
try
{
if (eventScope != null)
{
eventScope.Exit();
}
}
catch (Exception disposalException)
{
throw new ModelEventScope.ScopeException(disposalException, actionException);
}
throw;
}
}
void Prepare(ModelTransaction transaction)
{
// Resolve the root instance
Instance = EnsureInstance(transaction, Instance);
// Resolve added instances
var added = (ModelInstance[])Added;
for (int i = 0; i < added.Length; i++)
{
added[i] = EnsureInstance(transaction, added[i]);
}
// Resolve removed instances
var removed = (ModelInstance[])Removed;
for (int i = 0; i < removed.Length; i++)
{
removed[i] = EnsureInstance(transaction, removed[i]);
}
}
/// <summary>
/// Allows multiple <see cref="ModelTransaction"/> instances to be applied in sequence, or "chained",
/// by propogating information about newly created instances from one transaction to the next.
/// </summary>
public ModelTransaction Chain(ModelTransaction nextTransaction)
{
// Immediately exit if the transaction is being chained with itself
if (nextTransaction == this)
{
return(nextTransaction);
}
// Propogate the new instance cache forward to the next transaction
if (newInstances != null)
{
foreach (ModelInstance instance in newInstances.Values)
{
nextTransaction.RegisterNewInstance(instance);
}
}
// Link the next transaction to the previous transaction
nextTransaction.PreviousTransaction = this;
// Return the next transaction
return(nextTransaction);
}
public void Rollback(ModelTransaction transaction)
{
throw new NotSupportedException("Rollback is not supported by the ModelSaveEvent.");
}
public void Perform(ModelTransaction transaction)
{
Instance = EnsureInstance(transaction, Instance);
Instance.Save();
}
/// <summary>
/// Verifies that the specified <see cref="ModelInstance"/> refers to a valid real instance
/// and if not, uses the type and id information to look up the real instance.
/// </summary>
/// <param name="transaction"></param>
/// <param name="instance"></param>
/// <returns></returns>
protected ModelInstance EnsureInstance(ModelTransaction transaction, ModelInstance instance)
{
return(instance.Instance == null?transaction.GetInstance(instance.Type, instance.Id) : instance);
}
