BCUninstaller/Bulk-Crap-Uninstaller · error · ArgumentException

Argument {argument} has already been defined

Error message

Argument {argument} has already been defined

What it means

AddSingle enforces that an argument key appears exactly once. Calling it a second time for the same key (when the key already exists in _parameters) throws ArgumentException, since a single-value argument must not be defined more than once. Contrast with Add(), which allows multiple values per key.

Source

Thrown at source/KlocTools/IO/Arguments.cs:162

        /// <summary>
        /// Adds the specified argument.
        /// </summary>
        /// <param name="argument">The argument.</param>
        /// <param name="value">The value.</param>
        public void Add(string argument, string value)
        {
            if (!_parameters.ContainsKey(argument))
                _parameters.Add(argument, new Collection<string>());

            _parameters[argument].Add(value);
        }

        public void AddSingle(string argument, string value)
        {
            if (!_parameters.ContainsKey(argument))
                _parameters.Add(argument, new Collection<string>());
            else
                throw new ArgumentException($"Argument {argument} has already been defined");

            _parameters[argument].Add(value);
        }

        public void Remove(string argument)
        {
            if (_parameters.ContainsKey(argument))
                _parameters.Remove(argument);
        }

        /// <summary>
        /// Determines whether the specified argument is true.
        /// </summary>
        /// <param name="argument">The argument.</param>
        /// <returns>
        ///     <c>true</c> if the specified argument is true; otherwise, <c>false</c>.
        /// </returns>
        public bool IsTrue(string argument)

View on GitHub (pinned to 608321de98)

Solutions

1. Use Add() instead of AddSingle() when multiple values are acceptable.
2. Call Remove(argument) before AddSingle() to replace the value.
3. Deduplicate the input before parsing it into the Arguments object.

Example fix

// before
args.AddSingle("mode", "a");
args.AddSingle("mode", "b"); // throws
// after
args.Remove("mode");
args.AddSingle("mode", "b");

if (args.Exists(argument)) args.Remove(argument);
args.AddSingle(argument, value);

When it happens

Trigger: Parsing CLI input where the same flag is provided twice and routed through AddSingle; a programmatic double-add of the same key.

Common situations: Duplicate flags in a script; two code paths adding the same argument; merged argument sources without dedup.

Related errors

• {argument} has been specified more than once, expecting sing
• Pattern doesn't match the string. Sum of the pattern's parts
• New value must be equal to or in between the minimum and max
• Minimum value must be lower than or equal to the maximum val
• Font size must be higher than 0

AI-assisted analysis of BCUninstaller/Bulk-Crap-Uninstaller@608321de98 (2026-08-13). Data as JSON: /api/errors/f947b934db835f10. Report an issue: GitHub.