dotnet/machinelearning · error · ArgumentOutOfRangeException

Strings.IndexIsGreaterThanColumnLength

Error message

Strings.IndexIsGreaterThanColumnLength

What it means

StringDataFrameColumn stores rows in fixed-capacity buffers; GetBufferIndexContainingRowIndex maps a logical row index to a buffer. It throws ArgumentOutOfRangeException when rowIndex >= the column's Length, i.e. you asked for a row that does not exist in this column.

Source

Thrown at src/Microsoft.Data.Analysis/DataFrameColumns/StringDataFrameColumn.cs:107

        {
            var column = inPlace ? this : Clone();

            for (long i = 0; i < column.Length; i++)
            {
                var value = column[i];

                if (value != null)
                    column[i] = func(value);
            }

            return column;
        }

        private int GetBufferIndexContainingRowIndex(long rowIndex)
        {
            if (rowIndex >= Length)
            {
                throw new ArgumentOutOfRangeException(Strings.IndexIsGreaterThanColumnLength, nameof(rowIndex));
            }
            return (int)(rowIndex / MaxCapacity);
        }

        protected override object GetValue(long rowIndex)
        {
            int bufferIndex = GetBufferIndexContainingRowIndex(rowIndex);
            return _stringBuffers[bufferIndex][(int)(rowIndex % MaxCapacity)];
        }

        protected override IReadOnlyList<object> GetValues(long startIndex, int length)
        {
            var ret = new List<object>();
            int bufferIndex = GetBufferIndexContainingRowIndex(startIndex);
            int bufferOffset = (int)(startIndex % MaxCapacity);
            while (ret.Count < length && bufferIndex < _stringBuffers.Count)
            {
                for (int i = bufferOffset; ret.Count < length && i < _stringBuffers[bufferIndex].Count; i++)

View on GitHub (pinned to 7b76e69cf9)

Solutions

1. Check rowIndex against column.Length before indexing
2. Ensure loops use strict less-than (i < column.Length)
3. Verify the column was fully populated (same row count as the DataFrame)
4. Wrap indexed access in try/catch for ArgumentOutOfRangeException in data-driven code

Example fix

// before
var value = column[column.Length];
// after
if (rowIndex >= 0 && rowIndex < column.Length)
    var value = column[rowIndex];

if (rowIndex < 0 || rowIndex >= column.Length) throw new ArgumentOutOfRangeException(nameof(rowIndex));

bool IsValidIndex(long i, long length) => i >= 0 && i < length;

try { var v = column[rowIndex]; } catch (ArgumentOutOfRangeException) { /* handle missing row */ }

When it happens

Trigger: Accessing this[rowIndex] or bufferIndex with an index equal to or beyond the column's current row count; often from passing a 0-based index that is actually a count, or using a DataFrame with more rows than this column.

Common situations: Off-by-one loops (i <= Length), indexing after rows were removed, joining columns of mismatched lengths.

Related errors

• nameof(row)
• Strings.IndexIsGreaterThanColumnLength
• nameof(row)
• nameof(groupByColumnIndex)
• row

AI-assisted analysis of dotnet/machinelearning@7b76e69cf9 (2026-09-11). Data as JSON: /api/errors/859df43cd7264fbb. Report an issue: GitHub.