The following code sample demonstrates explicit and implicit locking, within and outside of transaction state.
// Lock objects outside transaction state.
TimeSpan timeOut = TimeSpan.FromSeconds(10);
context.Lock(obj1, LockType.Reserve, LockDuration.Transaction, timeOut);
context.Lock(obj2, LockType.Shared, LockDuration.Transaction, timeOut);
context.Lock(obj3, LockType.Shared, LockDuration.Session, timeOut);
using (System.Data.IDbTransaction tran = context.BeginTransaction())
{
// Lock an object in transaction state.
context.Lock(obj4, LockType.Exclusive, LockDuration.Transaction, timeOut);
coll1.Add(obj1); // Acquires an implicit exclusive lock on coll1.
// Acquire an explicit update lock. This can only be done in transaction state.
context.Lock(coll2, LockType.Update, LockDuration.Transaction, timeOut);
coll2.Add(obj2); // No implicit lock, as coll2 is already locked.
context.Unlock(obj2); // This is ignored in transaction state.
context.Unlock(obj3); // This is ignored in transaction state.
obj5.Attr1 = "X"; // Acquires an implicit exclusive lock.
tran.Commit(); // Upgrades coll2’s update lock to exclusive,
// commits the updates,
// then unlocks coll1, coll2, obj1, obj2, obj4, and obj5.
// obj3 remains locked as it has session duration.
}
context.Unlock(obj3); // This will unlock obj3.
// Specify implicit update locks are to be used.
context.SetImplicitUpdatingLockType(LockType.Update);
using (System.Data.IDbTransaction tran = context.BeginTransaction())
{
coll3.Add(obj2); // Acquires an implicit update lock on coll3.
tran.Commit(); // Upgrades the update lock to an exclusive lock,
// commits the update,
// then unlocks coll3.
}
context.SetImplicitUpdatingLockType(LockType.Exclusive);