microsoft/aspire · error · ArgumentException

Must not be null or empty

Error message

Must not be null or empty

What it means

Thrown by Guard.ThrowIfNullOrEmpty in the vendored ConfluentKafka instrumentation's Guard helper when a required string parameter is null or the empty string. It wraps ArgumentException with the offending parameter name and asserts the value is non-null on exit. It guards required string configuration such as names, keys, or identifiers.

Solutions

1. Read paramName from the ArgumentException and supply a non-empty value for that argument before the call.
2. Validate string inputs with Guard.ThrowIfNullOrEmpty or ArgumentException.ThrowIfNullOrEmpty at your own boundary.
3. Trace back the string to its source (config/env var) and fix the empty value there.

Example fix

// before
var bootstrap = configuration["Kafka:BootstrapServers"]; // ""
UseBootstrapServers(bootstrap);

// after
var bootstrap = configuration["Kafka:BootstrapServers"];
ArgumentException.ThrowIfNullOrEmpty(bootstrap);
UseBootstrapServers(bootstrap);

if (string.IsNullOrEmpty(value))
{
    throw new ArgumentException("Must not be null or empty", nameof(value));
}

try
{
    instrumented.Configure(name);
}
catch (ArgumentException ex) when (ex.ParamName == "name")
{
    logger.LogError(ex, "'name' must be a non-empty string");
}

When it happens

Trigger: Calling a guarded API with a required string argument set to null or "", e.g. an empty bootstrap servers string, empty operation/topic name, or unset configuration value passed straight through.

Common situations: Connection strings or bootstrap servers read from configuration that resolved to an empty string; missing environment variables whose defaults are empty; string fields initialized to "" instead of real values.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• Must not be null or whitespace
• Must be in the range
• Must not be null
• Must not be null or empty
• Must not be null or whitespace

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/0996d49d91fd33cc. Report an issue: GitHub.

Appendix: source

Thrown at src/Vendoring/OpenTelemetry.Instrumentation.ConfluentKafka/Shared/Guard.cs:82

            if (value is null)
            {
                throw new ArgumentNullException(paramName, "Must not be null");
            }
        }

        /// <summary>
        /// Throw an exception if the value is null or empty.
        /// </summary>
        /// <param name="value">The value to check.</param>
        /// <param name="paramName">The parameter name to use in the thrown exception.</param>
        [DebuggerHidden]
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void ThrowIfNullOrEmpty([NotNull] string? value, [CallerArgumentExpression("value")] string? paramName = null)
#pragma warning disable CS8777 // Parameter must have a non-null value when exiting.
        {
            if (string.IsNullOrEmpty(value))
            {
                throw new ArgumentException("Must not be null or empty", paramName);
            }
        }
#pragma warning restore CS8777 // Parameter must have a non-null value when exiting.

        /// <summary>
        /// Throw an exception if the value is null or whitespace.
        /// </summary>
        /// <param name="value">The value to check.</param>
        /// <param name="paramName">The parameter name to use in the thrown exception.</param>
        [DebuggerHidden]
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void ThrowIfNullOrWhitespace([NotNull] string? value, [CallerArgumentExpression("value")] string? paramName = null)
#pragma warning disable CS8777 // Parameter must have a non-null value when exiting.
        {
            if (string.IsNullOrWhiteSpace(value))
            {
                throw new ArgumentException("Must not be null or whitespace", paramName);
            }

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