mRemoteNG/mRemoteNG · error · ArgumentException

Option key cannot exceed 255 characters.

Error message

Option key cannot exceed 255 characters.

What it means

Thrown by OptionsRepository.ValidateKey when option.Key.Length > 255. The SQLite schema defines key as TEXT but the repository enforces a 255-character business cap (matching the index/key budget). Longer keys are rejected with ArgumentException.

Source

Thrown at mRemoteNG/Config/Settings/OptionsRepository.cs:120

        }

        #region Validation

        private static void ValidateOption(OptionInfo option)
        {
            if (option == null)
                throw new ArgumentNullException(nameof(option));

            ValidateKey(option.Key);
        }

        private static void ValidateKey(string key)
        {
            if (string.IsNullOrWhiteSpace(key))
                throw new ArgumentException("Option key cannot be null or whitespace.", nameof(key));

            if (key.Length > 255)
                throw new ArgumentException("Option key cannot exceed 255 characters.", nameof(key));
        }

        private static void ValidateCategory(string category)
        {
            if (string.IsNullOrWhiteSpace(category))
                throw new ArgumentException("Category cannot be null or whitespace.", nameof(category));

            if (category.Length > 255)
                throw new ArgumentException("Category cannot exceed 255 characters.", nameof(category));
        }

        private static void ValidateId(int id)
        {
            if (id <= 0)
                throw new ArgumentException("ID must be greater than 0.", nameof(id));
        }

        #endregion

View on GitHub (pinned to 9211babf35)

Solutions

1. Keep keys short identifiers (e.g. 'ui.theme', 'timeout.seconds'); store long data in Value, not Key.
2. Hash or truncate long identifiers before using them as a key (ensure uniqueness with a prefix/suffix).
3. Validate key.Length <= 255 in your input layer before calling the repository.
4. If you genuinely need long keys, raise the cap in ValidateKey and the schema.

Example fix

// before
await repo.AddOptionAsync(new OptionInfo { Key = veryLongString });

// after
const int MaxKey = 255;
string key = veryLongString.Length > MaxKey
    ? veryLongString.Substring(0, MaxKey)
    : veryLongString;
await repo.AddOptionAsync(new OptionInfo { Key = key });

const int MaxKey = 255;
if (option.Key.Length > MaxKey)
    throw new ArgumentException($"Option key exceeds {MaxKey} characters.");

static bool IsKeyWithinLimit(string key) => key != null && key.Length <= 255;

try { await repo.AddOptionAsync(option); }
catch (ArgumentException ex) when (ex.Message.Contains("255"))
{ option.Key = option.Key.Substring(0, 255); await repo.AddOptionAsync(option); }

When it happens

Trigger: Calling any key-accepting method with a key longer than 255 characters — e.g. a generated GUID-heavy string, a base64 blob, or a path used as a key.

Common situations: Using a full file path, URL, or serialized object as the option key; concatenating identifiers without a length budget.

Related errors

• Category cannot exceed 255 characters.
• An option with key '{option.Key}' already exists.
• Option key cannot be null or whitespace.
• Category cannot be null or whitespace.
• ID must be greater than 0.

AI-assisted analysis of mRemoteNG/mRemoteNG@9211babf35 (2026-08-13). Data as JSON: /api/errors/0a906a0bb5e2c9d8. Report an issue: GitHub.