Unity-Technologies/UnityCsReference · error · ArgumentNullException

columnIndices

Error message

columnIndices

What it means

Thrown by MultiColumnHeader.SetSortingColumns when the columnIndices array is null. The method pairs each column index with a sort-ascending flag, so a null column array makes the operation impossible.

Source

Thrown at Editor/Mono/GUI/TreeView/MultiColumnHeader.cs:72

            get { return m_State; }
            set
            {
                if (value == null)
                    throw new ArgumentNullException("state", "MultiColumnHeader state is not allowed to be null");
                m_State = value;
            }
        }

        public MultiColumnHeader(MultiColumnHeaderState state)
        {
            m_State = state;
            m_HeaderButtonsControlID = GUIUtility.GetPermanentControlID();
        }

        public void SetSortingColumns(int[] columnIndices, bool[] sortAscending)
        {
            if (columnIndices == null)
                throw new ArgumentNullException("columnIndices");

            if (sortAscending == null)
                throw new ArgumentNullException("sortAscending");

            if (columnIndices.Length != sortAscending.Length)
                throw new ArgumentException("Input arrays should have same length");

            if (columnIndices.Length > state.maximumNumberOfSortedColumns)
                throw new ArgumentException("The maximum number of sorted columns is " + state.maximumNumberOfSortedColumns + ". Trying to set " + columnIndices.Length + " columns.");

            if (columnIndices.Length != columnIndices.DistinctCount())
                throw new ArgumentException("Duplicate column indices are not allowed", "columnIndices");

            bool changed = false;

            if (!columnIndices.AsSpan().SequenceEqual(state.sortedColumns))
            {
                state.sortedColumns = columnIndices;

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Pass an empty int array (Array.Empty<int>()) instead of null to clear sorting.
2. Initialize columnIndices before the call; default to the currently sorted columns.
3. Null-check at the caller and substitute a sensible default.

Example fix

// before
header.SetSortingColumns(sortCols, sortAsc); // sortCols may be null

// after
int[] cols = sortCols ?? Array.Empty<int>();
bool[] asc = sortAsc ?? Array.Empty<bool>();
header.SetSortingColumns(cols, asc);

int[] cols = columnIndices ?? Array.Empty<int>();

static bool IsValidSortArray(int[] a) => a != null;

When it happens

Trigger: Calling SetSortingColumns(null, sortFlags); passing a lazily-initialized array that was never populated.

Common situations: Resetting sort to defaults but passing null instead of an empty array; a binding that yields null when no sort columns are configured.

Related errors

• MultiColumnHeader state is not allowed to be null
• sortAscending
• columns are no allowed to be null
• visibleColumns should not be set to null
• Input arrays should have same length

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/054fc54abfacc174. Report an issue: GitHub.