JamesNK/Newtonsoft.Json · error · ArgumentOutOfRangeException

Index is equal to or greater than Count.

Error message

Index is equal to or greater than Count.

What it means

RemoveItemAt throws ArgumentOutOfRangeException when index >= ChildrenTokens.Count, i.e. the slot does not exist. The upper bound is Count-1.

Source

Thrown at Src/Newtonsoft.Json/Linq/JContainer.cs:423

            {
                OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item, index));
            }
#endif

            return true;
        }

        internal virtual void RemoveItemAt(int index)
        {
            IList<JToken> children = ChildrenTokens;

            if (index < 0)
            {
                throw new ArgumentOutOfRangeException(nameof(index), "Index is less than 0.");
            }
            if (index >= children.Count)
            {
                throw new ArgumentOutOfRangeException(nameof(index), "Index is equal to or greater than Count.");
            }

            CheckReentrancy();

            JToken item = children[index];
            JToken? previous = (index == 0) ? null : children[index - 1];
            JToken? next = (index == children.Count - 1) ? null : children[index + 1];

            if (previous != null)
            {
                previous.Next = next;
            }
            if (next != null)
            {
                next.Previous = previous;
            }

            item.Parent = null;

View on GitHub (pinned to 4f73e74372)

Solutions

1. Loop backwards when removing, or recompute Count each iteration.
2. Validate index < container.Count before calling RemoveAt.
3. Prefer Remove(item) when removing by reference rather than by position.

Example fix

// before
for (int i = 0; i < arr.Count; i++) arr.RemoveAt(i);
// after
for (int i = arr.Count - 1; i >= 0; i--) arr.RemoveAt(i);

if (index >= arr.Count || index < 0) return;
arr.RemoveAt(index);

try { arr.RemoveAt(index); }
catch (ArgumentOutOfRangeException ex) when (ex.ParamName == "index") {
    // index out of range; recompute and retry or skip
}

When it happens

Trigger: jArray.RemoveAt(jArray.Count); a stale/cached count larger than the live collection; loop variable overshooting.

Common situations: Iterating and removing in a forward loop without adjusting indices; cached Count after items were removed.

Related errors

• Index is less than 0.
• Index must be within the bounds of the List.
• arrayIndex is less than 0.
• arrayIndex is equal to or greater than the length of array.
• The number of elements in the source JObject is greater than

AI-assisted analysis of JamesNK/Newtonsoft.Json@4f73e74372 (2026-08-07). Data as JSON: /api/errors/31c4c3a8e653ffd6. Report an issue: GitHub.