Sequential async execution in .NET: SemaphoreSlim, Channels, and TaskFlow
Familiar pattern? using System ; using System.Threading ; using System.Threading.Tasks ; public sealed class InstrumentController : IDisposable { private readonly IInstrumentSession _session ; private readonly SemaphoreSlim _gate = new ( 1 , 1 ); private bool _disposed ; // Takes exclusive ownership of a session that is not thread-safe. public InstrumentController ( IInstrumentSession session )…
The provided example demonstrates a pattern for managing concurrent access to a non-thread-safe resource in .NET. The `InstrumentController` class owns an `IInstrumentSession` object, which is not thread-safe. To ensure exclusive access to the session, the class uses a `SemaphoreSlim` with a count of 1, allowing only one thread to access the session at a time.
The `InstrumentController` class exposes methods for setting the range, reading, and calibrating the instrument asynchronously. Each method acquires the semaphore before performing the corresponding operation and releases it afterward. This ensures that the session is not accessed concurrently by multiple threads, preventing potential data races or inconsistent states.
The disposal contract of the `InstrumentController` class is crucial. The `Dispose` method must be called only once, and it must wait for all ongoing asynchronous operations to complete before releasing the resources. This is achieved by marking the object as disposed and disposing of the `IInstrumentSession` and `SemaphoreSlim` in a finally block, ensuring that the disposal process is not concurrent with other members.
The example showcases a simple yet effective way to manage concurrent access to a non-thread-safe resource using a `SemaphoreSlim`. It demonstrates the importance of proper resource management and synchronization in concurrent programming scenarios.
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