litedb-org/LiteDB · error · ArgumentNullException

Value cannot be null. (Parameter 'dict')

Error message

Value cannot be null. (Parameter 'dict')

What it means

Thrown when the BsonDocument constructor that accepts a ConcurrentDictionary<string, BsonValue> receives a null argument. The constructor copies elements from the supplied dictionary into the new document's internal storage, so a null source is rejected early via ArgumentNullException. This is a fail-fast guard before any iteration begins.

Source

Thrown at LiteDB/Document/BsonDocument.cs:22

using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using static LiteDB.Constants;

namespace LiteDB
{
    public class BsonDocument : BsonValue, IDictionary<string, BsonValue>
    {
        public BsonDocument()
            : base(BsonType.Document, new Dictionary<string, BsonValue>(StringComparer.OrdinalIgnoreCase))
        {
        }

        public BsonDocument(ConcurrentDictionary<string, BsonValue> dict)
            : this()
        {
            if (dict == null) throw new ArgumentNullException(nameof(dict));

            foreach(var element in dict)
            {
                this.Add(element);
            }
        }

        public BsonDocument(IDictionary<string, BsonValue> dict)
            : this()
        {
            if (dict == null) throw new ArgumentNullException(nameof(dict));

            foreach (var element in dict)
            {
                this.Add(element);
            }
        }

View on GitHub (pinned to f906a5f850)

Solutions

1. Check the dictionary for null before constructing the BsonDocument and either supply an empty ConcurrentDictionary or handle the missing-data case explicitly.
2. Use the parameterless `new BsonDocument()` when you have no initial data, then add entries individually.
3. Trace upstream to find why the ConcurrentDictionary is null and fix the source.

Example fix

// before
var doc = new BsonDocument(maybeNullDict);
// after
var doc = new BsonDocument(maybeNullDict ?? new ConcurrentDictionary<string, BsonValue>());

if (dict == null) throw new ArgumentException("Source dictionary is required.");
var doc = new BsonDocument(dict);

static bool IsValidDocumentSource(ConcurrentDictionary<string, BsonValue> dict) => dict != null;

try { var doc = new BsonDocument(dict); }
catch (ArgumentNullException ex) when (ex.ParamName == "dict")
{ /* log and supply empty doc or rethrow with context */ }

When it happens

Trigger: Calling `new BsonDocument((ConcurrentDictionary<string, BsonValue>)null)` or passing a variable that resolved to null at runtime into the ConcurrentDictionary overload of the BsonDocument constructor.

Common situations: A dictionary retrieved from a cache, config, or upstream service is null because of a cache-miss or deserialization failure and is passed directly to BsonDocument without a null-check. Generic code that wraps dictionary creation and sometimes returns null.

Related errors

• Value cannot be null. (Parameter 'array')
• Value cannot be null. (Parameter 'items')
• Value cannot be null. (Parameter 'doc')
• Value cannot be null. (Parameter 'buffer')
• Value cannot be null. (Parameter 'collection')

AI-assisted analysis of litedb-org/LiteDB@f906a5f850 (2026-08-13). Data as JSON: /api/errors/854b1bf86163da35. Report an issue: GitHub.