TheAlgorithms/C-Sharp · error · ArgumentException

The sequence may only contain ones or zeros

Error message

The sequence may only contain ones or zeros

What it means

ThrowIfSequenceIsInvalid validates that a binary string sequence contains only '0' and '1' characters (via the Match regex/utility). It is used by the BitArray string constructor and Compile(sequence); any other character makes the sequence unparseable as binary, so an ArgumentException is thrown.

Solutions

1. Sanitize the input: strip whitespace/underscores and verify every character is '0' or '1' before constructing or calling Compile.
2. Trim the string and remove formatting characters (spaces, separators) that may have been added for readability.
3. If the input is decimal/hex, convert it to binary with Convert.ToString(value, 2) instead of passing it as a raw sequence.
4. Validate with a regex ^[01]+$ and reject or normalize invalid input at the boundary.

Example fix

// before
var ba = new BitArray("10 01"); // space -> throws

// after
var raw = "10 01";
var seq = raw.Replace(" ", "");
if (!System.Text.RegularExpressions.Regex.IsMatch(seq, "^[01]+$"))
    throw new ArgumentException("Invalid binary sequence");
var ba = new BitArray(seq);

bool IsValidSequence(string s) => System.Text.RegularExpressions.Regex.IsMatch(s?.Trim() ?? "", "^[01]+$");

bool IsBinaryString(string s) => !string.IsNullOrEmpty(s) && s.All(c => c is '0' or '1');

try { var ba = new BitArray(seq); } catch (ArgumentException ex) when (ex.Message.Contains("ones or zeros")) { /* sanitize and retry or reject input */ }

When it happens

Trigger: new BitArray("10a01") or Compile("12") — any string passed to the sequence constructor or Compile containing characters other than '0' and '1' (letters, whitespace, '+', '-', punctuation, etc.).

Common situations: Reading binary values from user input, config files, or HTTP payloads without sanitizing; copying bit strings with hidden whitespace or BOM characters; accidentally passing decimal strings like "102" as binary.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Value is too big to fit into Int64
• Value is too big to fit into Int32
• Capacity must be at least 1.
• The length of key should be divisible by 16
• Discount rate cannot be negative

AI-assisted analysis of TheAlgorithms/C-Sharp@96e2905cab (2026-09-13). Data as JSON: /api/errors/2958d1e82d100697. Report an issue: GitHub.

Appendix: source

Thrown at DataStructures/BitArray.cs:769

                return false;
            }
        }

        return true;
    }

    /// <summary>
    ///     Gets has-code of bit-array.
    ///     Assumes bit-array length must been smaller or equal to 32.
    /// </summary>
    /// <returns>hash-code for this BitArray instance.</returns>
    public override int GetHashCode() => ToInt32();

    private static void ThrowIfSequenceIsInvalid(string sequence)
    {
        if (!Match(sequence))
        {
            throw new ArgumentException("The sequence may only contain ones or zeros");
        }
    }

    /// <summary>
    ///     Utility method for checking a given sequence contains only zeros and ones.
    ///     This method will used in Constructor (sequence : string) and Compile(sequence : string).
    /// </summary>
    /// <param name="sequence">String sequence.</param>
    /// <returns>returns True if sequence contains only zeros and ones; False otherwise.</returns>
    private static bool Match(string sequence) => sequence.All(ch => ch == '0' || ch == '1');
}

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