Class AsyncReaderWriterLock

Implements an async/await friendly equivalent of ReaderWriterLock.

Inheritance

AsyncReaderWriterLock

Namespace: Neon.Tasks

Assembly: Neon.Common.dll

Syntax

public class AsyncReaderWriterLock

Remarks

This class can be used to grant a single writer task exclusive access to a resource or multiple reader tasks. This class is pretty easy to use. Simply instantiate an instance and then call GetReadLockAsync() or GetWriteLockAsync() within a using statement:

var rwLock = new AsyncReaderWriterLock();
using (await rwLock.GetReadLockAsync())
{
// Protected reading code
}
using (await rwLock.GetWriteLockAsync())
{
// Protected writing code
}

note

Be very sure to include the await within the using statement to avoid hard to debug problems. The await ensures that the using statement will dispose the acquired lock as opposed to the Task that returns the lock.

Applications that cannot use a using statement may release the lock explicitly by disposing the object returned by the lock method, like this:

var rwLock   = new AsyncReaderWriterLock();
var readLock = await rwLock.GetReadLockAsync();
// Protected reading code.
readLock.Dispose();

AsyncReaderWriterLock's Dispose() method ensures that any tasks waiting for a lock will be unblocked with an ObjectDisposedException.

This class is implemented is fairly simple and always favors writers over readers. Also, all waiting readers will be released together.

note

AsyncReaderWriterLock does not support any kind of reentrant Task locking support. Child tasks will be considered to be completely independent of the parent and will not inherit the parent's lock and a single task will not be able to acquire the same lock multiple times.

Constructors

AsyncReaderWriterLock()

Constructor.

Declaration

public AsyncReaderWriterLock()

Methods

Close()

Releases any important resources associated with the instance.

Declaration

public void Close()

Remarks

note

This method will cause a ObjectDisposedException to be thrown on any task waiting to acquire this lock.

Dispose()

Releases any important resources associated with the instance.

Declaration

public void Dispose()

Remarks

note

This method will cause a ObjectDisposedException to be thrown on any task waiting to acquire this lock.

Dispose(bool)

Releases any important resources associated with the instance.

Declaration

protected void Dispose(bool disposing)

Parameters

Type	Name	Description
bool	disposing	Pass `true` if the instance is being disposed as opposed to being finalized.

~AsyncReaderWriterLock()

Finalizer.

Declaration

protected ~AsyncReaderWriterLock()

GetReadLockAsync()

Acquires a non-exclusive read lock.

Declaration

public Task<IDisposable> GetReadLockAsync()

Returns

Type	Description
Task<IDisposable>	The IDisposable instance to be disposed to release the lock.

Remarks

note

This class allows multiple readers to hold the lock at any given time but requires that writers have exclusive access. Writers are given priority over readers.

Exceptions

Type	Condition
ObjectDisposedException	Thrown if the lock is disposed before or after this method is called.

GetWriteLockAsync()

Acquires an exclusive write lock.

Declaration

public NonDisposableTask<IDisposable> GetWriteLockAsync()

Returns

Type	Description
NonDisposableTask<IDisposable>	The IDisposable instance to be disposed to release the lock.

Remarks

note

This class allows multiple readers to hold the lock at any given time but requires that writers have exclusive access. Writers are given priority over readers.

Exceptions

Type	Condition
ObjectDisposedException	Thrown if the lock is disposed before or after this method is called.