JamesNK/Newtonsoft.Json · error · Exception

Cannot deserialize non-cubical array as multidimensional arr

Error message

Cannot deserialize non-cubical array as multidimensional array.

What it means

Thrown by CollectionUtils.CopyFromJaggedToMultidimensionalArray when the jagged-array representation of a deserialized multidimensional array has rows of unequal length (non-cubical). A multidimensional array (e.g. int[2,3]) is rectangular; if the JSON encodes rows with different lengths the resulting jagged structure is not cubical and cannot be copied into a rectangular array.

Source

Thrown at Src/Newtonsoft.Json/Utilities/CollectionUtils.cs:331

            return dimensions;
        }

        private static void CopyFromJaggedToMultidimensionalArray(IList values, Array multidimensionalArray, int[] indices)
        {
            int dimension = indices.Length;
            if (dimension == multidimensionalArray.Rank)
            {
                multidimensionalArray.SetValue(JaggedArrayGetValue(values, indices), indices);
                return;
            }

            int dimensionLength = multidimensionalArray.GetLength(dimension);
            IList list = (IList)JaggedArrayGetValue(values, indices);
            int currentValuesLength = list.Count;
            if (currentValuesLength != dimensionLength)
            {
                throw new Exception("Cannot deserialize non-cubical array as multidimensional array.");
            }

            int[] newIndices = new int[dimension + 1];
            for (int i = 0; i < dimension; i++)
            {
                newIndices[i] = indices[i];
            }

            for (int i = 0; i < multidimensionalArray.GetLength(dimension); i++)
            {
                newIndices[dimension] = i;
                CopyFromJaggedToMultidimensionalArray(values, multidimensionalArray, newIndices);
            }
        }

        private static object JaggedArrayGetValue(IList values, int[] indices)
        {
            IList currentList = values;

View on GitHub (pinned to 4f73e74372)

Solutions

Validate/normalize the JSON so every row array has the same length before deserializing.
Deserialize into a jagged array (T[][]) instead of a rectangular multidimensional array (T[,]).
Use a custom JsonConverter that pads or rejects non-rectangular input explicitly.
Fix the producer to always emit rectangular data.

Example fix

// before: non-cubical JSON into int[,]
int[,] grid = JsonConvert.DeserializeObject<int[,]>("[[1,2,3],[4,5]]");
// after: deserialize jagged then convert
int[][] jagged = JsonConvert.DeserializeObject<int[][]>("[[1,2,3],[4,5,0]]");
int[,] grid = ToRectangular(jagged);

Defensive patterns

Strategy: validation

Validate before calling

bool IsCubical<T>(T[][] jagged) => jagged.Length == 0 || jagged.All(r => r.Length == jagged[0].Length);

Type guard

static bool IsCubical(Array jagged) { if (jagged.Length == 0) return true; int len = ((Array)jagged.GetValue(0)).Length; for (int i=1;i<jagged.Length;i++) if (((Array)jagged.GetValue(i)).Length != len) return false; return true; }

Try / catch

try { var arr = JsonConvert.DeserializeObject<int[,]>(json); }
catch (Exception ex) when (ex.Message.Contains("non-cubical array")) {
    logger.Error(ex, "rows have unequal length; deserialize as jagged or normalize JSON."); throw;
}

Prevention

Validate row lengths are uniform before deserializing into a multidimensional array.
Prefer T[][] (jagged) target types for variable-length row data.
Use a custom JsonConverter to enforce rectangular shape with a clear error.
Ensure producers always emit rectangular data.

When it happens

Trigger: Deserializing JSON into a multidimensional array (e.g. int[,] target) where the JSON arrays per row have differing counts, e.g. [[1,2,3],[4,5]].

Common situations: Source JSON produced by a jagged-array producer rather than a rectangular one; sparse matrix data; mismatched schema where the producer assumes jagged but the consumer declares a multidimensional array; malformed/partial payload from an external API.

Related errors

AI-assisted analysis of JamesNK/Newtonsoft.Json@4f73e74372 (2026-08-07). Data as JSON: /api/errors/faab217ed02727c9. Report an issue: GitHub.