litedb-org/LiteDB · error · ArgumentException

At least two Query should be passed

Error message

At least two Query should be passed

What it means

Query.And(params BsonExpression[] queries) folds many filters with AND. At Query.cs:206 it throws ArgumentException("At least two Query should be passed") when queries is null or has fewer than two elements, because AND is a binary operation that needs at least two operands. Passing a single filter or none is a usage error, not a null-element problem. This is an ArgumentException, not ArgumentNullException.

Source

Thrown at LiteDB/Client/Structures/Query.cs:206

        public static QueryAny Any() => new QueryAny();

        /// <summary>
        /// Returns document that exists in BOTH queries results. If both queries has indexes, left query has index preference (other side will be run in full scan)
        /// </summary>
        public static BsonExpression And(BsonExpression left, BsonExpression right)
        {
            if (left == null) throw new ArgumentNullException(nameof(left));
            if (right == null) throw new ArgumentNullException(nameof(right));

            return $"({left.Source} AND {right.Source})";
        }

        /// <summary>
        /// Returns document that exists in ALL queries results.
        /// </summary>
        public static BsonExpression And(params BsonExpression[] queries)
        {
            if (queries == null || queries.Length < 2) throw new ArgumentException("At least two Query should be passed");

            var left = queries[0];

            for (int i = 1; i < queries.Length; i++)
            {
                left = And(left, queries[i]);
            }

            return left;
        }

        /// <summary>
        /// Returns documents that exists in ANY queries results (Union).
        /// </summary>
        public static BsonExpression Or(BsonExpression left, BsonExpression right)
        {
            if (left == null) throw new ArgumentNullException(nameof(left));
            if (right == null) throw new ArgumentNullException(nameof(right));

View on GitHub (pinned to f906a5f850)

Solutions

1. Guard the collection: if fewer than 2 filters, return the single one (or Query.All) instead of calling And.
2. Use the binary Query.And(left, right) when you know there are exactly two.
3. Ensure at least two non-null elements are passed.

Example fix

// before
var q = Query.And(filters.ToArray()); // filters may have 0 or 1 element

// after
var q = filters.Count switch
{
    0 => Query.All(),
    1 => filters[0],
    _ => Query.And(filters.ToArray())
};

var q = filters.Count switch
{
    0 => Query.All(),
    1 => filters[0],
    _ => Query.And(filters.ToArray())
};

static bool CanFold(IReadOnlyList<BsonExpression> q) =>
    q is not null && q.Count >= 2 && q.All(x => x is not null);

When it happens

Trigger: Calling Query.And(), Query.And(single), Query.And(arr) where arr.Length < 2, or Query.And(null). A null array also triggers it (the check uses ||).

Common situations: Dynamically collecting filters from a request where only one (or zero) was provided; passing a list whose Count was not checked before folding.

Related errors

• Value cannot be null. (Parameter 'left')
• field
• Value cannot be null. (Parameter 'field')
• Value cannot be null. (Parameter 'arrayField')
• Multiple OrderBy calls are not supported. Use ThenBy for add

AI-assisted analysis of litedb-org/LiteDB@f906a5f850 (2026-08-13). Data as JSON: /api/errors/3bdf7243512576c4. Report an issue: GitHub.