dotnet/BenchmarkDotNet · error · ArgumentNullException

Value cannot be null. (Parameter 'values')

Error message

Value cannot be null. (Parameter 'values')

What it means

CreateArgumentTextRepresentation throws ArgumentNullException(nameof(values)) when the values array is null. Because values is a params parameter, a null array is only produced by explicitly passing null (e.g. new MsBuildProperty("name", null) where the compiler binds null to string[]); omitting values yields an empty array, not null.

Source

Thrown at src/BenchmarkDotNet/Jobs/Argument.cs:126

    /// An MSBuild property argument (<c>/p:name=value</c>).
    /// It escapes MSBuild special characters in the value (for example, semicolons) so that
    /// list-like values can be passed without manual encoding.
    /// </summary>
    [PublicAPI]
    public class MsBuildProperty : MsBuildArgument
    {
        public MsBuildProperty(string name, params string[] values)
            : base(CreateArgumentTextRepresentation(name, values), escapeSpecialCharacters: true)
        {
        }

        private static string CreateArgumentTextRepresentation(string name, string[] values)
        {
            if (string.IsNullOrWhiteSpace(name))
                throw new ArgumentException("Property name must be non-empty.", nameof(name));

            if (values is null)
                throw new ArgumentNullException(nameof(values));

            for (int i = 0; i < values.Length; i++)
                if (values[i] is null)
                    throw new ArgumentException("Property values can not contain null.", nameof(values));

            string value = values.Length switch
            {
                0 => string.Empty,
                1 => values[0],
                _ => string.Join(";", values)
            };

            return $"/p:{name}={value}";
        }
    }
}

View on GitHub (pinned to b515068b61)

Solutions

1. Omit values entirely for an empty property: new MsBuildProperty("name").
2. Coalesce a null array to an empty one before passing: values ?? Array.Empty<string>().
3. Pass a concrete value: new MsBuildProperty("name", "value").

Example fix

// before
job.WithArgument(new MsBuildProperty("MyCustomSetting", null));

// after
job.WithArgument(new MsBuildProperty("MyCustomSetting"));

var safeValues = values ?? Array.Empty<string>();
job.WithArgument(new MsBuildProperty(name, safeValues));

When it happens

Trigger: Calling new MsBuildProperty("name", null) (null binds to the params array), or passing a string[] variable that is null as the values argument.

Common situations: Passing a single null literal expecting an empty value, forwarding a possibly-null array variable, or constructing properties in a loop over a null collection.

Related errors

• Property name must be non-empty.
• The value {value} is not assignable to {characteristic} prop
• String cannot be empty.
• String cannot be empty or whitespace.
• {name} can't be null

AI-assisted analysis of dotnet/BenchmarkDotNet@b515068b61 (2026-08-13). Data as JSON: /api/errors/09e3130f779bc588. Report an issue: GitHub.