Find the bugWhen you can't rely on your own identity
time to read 2 min | 234 words

We had a need to generate unique ids for connections in our db. We used the following code:

public class NotificationsClientConnection : IDisposable
{
    private static int _counter = 0;

    private readonly WebSocket _webSocket;
    private readonly DocumentDatabase _documentDatabase;
    private readonly DateTime _startedAt;


    public NotificationsClientConnection(WebSocket webSocket, DocumentDatabase documentDatabase)
    {
        _webSocket = webSocket;
        _documentDatabase = documentDatabase;
        _startedAt = SystemTime.UtcNow;
    }

    public int Id => Interlocked.Increment(ref _counter);

    public TimeSpan Age => SystemTime.UtcNow - _startedAt;
}

Do you see the bug? It is a subtle one.

When you are ready, peek below.

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The issue is in the following line:

    public int Id => Interlocked.Increment(ref _counter);

The intent was to create a field that would be initialized on startup. Unfortunately, the usage of the lambda symbol "=>" instead of assignment "=" turned that into a computed property, which will return a new value on every call.

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