litedb-org/LiteDB · error · ArgumentNullException

engine

Error message

engine

What it means

ArgumentNullException thrown by the LiteDatabase(ILiteEngine, ...) constructor when engine is null. This overload wraps a pre-existing engine instance (e.g. a shared or mocked ILiteEngine); a null engine leaves LiteDatabase with nothing to delegate to, so it is rejected immediately.

Source

Thrown at LiteDB/Client/Database/LiteDatabase.cs:98

                    // Without a dedicated log stream the WAL lives purely in memory; force
                    // checkpointing to ensure commits reach the underlying data stream.
                    var originalCheckpointSize = _engine.Pragma(Pragmas.CHECKPOINT);

                    if (originalCheckpointSize != 1)
                    {
                        _engine.Pragma(Pragmas.CHECKPOINT, 1);
                        _checkpointOverride = originalCheckpointSize;
                    }
                }
            }
        }

        /// <summary>
        /// Start LiteDB database using a pre-exiting engine. When LiteDatabase instance dispose engine instance will be disposed too
        /// </summary>
        public LiteDatabase(ILiteEngine engine, BsonMapper mapper = null, bool disposeOnClose = true)
        {
            _engine = engine ?? throw new ArgumentNullException(nameof(engine));
            _mapper = mapper ?? BsonMapper.Global;
            _disposeOnClose = disposeOnClose;
        }

        #endregion

        #region Collections

        /// <summary>
        /// Get a collection using an entity class as strong typed document. If collection does not exist, create a new one.
        /// </summary>
        /// <param name="name">Collection name (case insensitive)</param>
        /// <param name="autoId">Define autoId data type (when object contains no id field)</param>
        public ILiteCollection<T> GetCollection<T>(string name, BsonAutoId autoId = BsonAutoId.ObjectId)
        {
            return new LiteCollection<T>(name, autoId, _engine, _mapper);
        }

View on GitHub (pinned to f906a5f850)

Solutions

1. Provide a real or mock ILiteEngine, e.g. new LiteDatabase(new LiteEngine(settings)).
2. Register ILiteEngine in the DI container so resolution succeeds.
3. Null-check the engine at the call site with a descriptive error before constructing LiteDatabase.

Example fix

// before
var db = new LiteDatabase((ILiteEngine)null);

// after
var engine = engineFactory.Create() ?? throw new InvalidOperationException("Engine factory returned null.");
var db = new LiteDatabase(engine);

ILiteEngine engine = engineFactory.Create()
    ?? throw new InvalidOperationException("Engine factory returned null; check DI registration.");
var db = new LiteDatabase(engine);

static bool HasEngine(ILiteEngine engine) => engine != null;

When it happens

Trigger: Constructing new LiteDatabase((ILiteEngine)null); a DI container resolving ILiteEngine to null; passing a factory result that returned null; wiring a mock engine in tests but forgetting to instantiate it.

Common situations: Dependency injection registration missing for ILiteEngine; a factory/orchestrator returning null on misconfiguration; test setup forgetting to create the mock engine.

Related errors

• connectionString
• stream
• name
• oldName
• newName

AI-assisted analysis of litedb-org/LiteDB@f906a5f850 (2026-08-13). Data as JSON: /api/errors/ee0c93cf503afbce. Report an issue: GitHub.