ReaderWriterLockSlim Constructor ()

The following example shows a simple synchronized cache that holds strings with integer keys. An instance of ReaderWriterLockSlim is used to synchronize access to the Dictionary<TKey, TValue> that serves as the inner cache. The parameterless constructor is used to create the lock.

The example includes simple methods to add to the cache, delete from the cache, and read from the cache. To demonstrate time-outs, the example includes a method that adds to the cache only if it can do so within a specified time-out.

To demonstrate upgradeable mode, the example includes a method that retrieves the value associated with a key and compares it with a new value. If the value is unchanged, the method returns a status indicating no change. It no value is found for the key, the key/value pair is inserted. If the value has changed, it is updated. Upgradeable mode allows the thread to upgrade from read access to write access as needed, without the risk of deadlocks.

The example includes a nested enumeration that specifies the return values for the method that demonstrates upgradeable mode.

The example uses the default constructor to create the lock, so recursion is not allowed. Programming the ReaderWriterLockSlim is simpler and less prone to error when the lock does not allow recursion.

The following code then uses the SynchronizedCache object to store a dictionary of vegetable names. It creates three tasks. The first writes the names of vegetables stored in an array to a SynchronizedCache instance. The second and third task display the names of the vegetables, the first in ascending order (from low index to high index), the second in descending order. The final task searches for the string "cucumber" and, when it finds it, calls the EnterUpgradeableReadLock method to substitute the string "green bean".