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 StackExchangeRedis instrumentation's Guard helper when a required string parameter is null or empty. On .NET targets it delegates to ArgumentException.ThrowIfNullOrEmpty; otherwise it throws ArgumentException with "Must not be null or empty". Guards required string values such as names or configuration strings.

Solutions

1. Supply a valid non-empty value for the argument named in the exception.
2. Fix the configuration source that yielded the empty string (missing key, blank entry).
3. Validate with ArgumentException.ThrowIfNullOrEmpty at your own boundary for clearer diagnostics.

Example fix

// before
var connStr = configuration["Redis:ConnectionString"]; // null
UseConnectionString(connStr);

// after
var connStr = configuration["Redis:ConnectionString"];
ArgumentException.ThrowIfNullOrEmpty(connStr);
UseConnectionString(connStr);

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

try
{
    AddRedisInstrumentation(o => o.ConnectionString = connectionString);
}
catch (ArgumentException ex) when (ex.ParamName == "connectionString")
{
    logger.LogError(ex, "connection string missing from configuration");
}

When it happens

Trigger: Passing null or "" to a guarded string parameter, e.g. an empty connection string, empty service name, or unset configuration key read from configuration that defaulted to empty.

Common situations: Missing environment variables defaulting to empty; connection strings defined but left blank in appsettings; string interpolation producing "" when an upstream value is missing.

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 not be null
• Must not be null or empty
• Must not be null or whitespace
• Error message cannot be null or empty.

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/dbb13ea4a140936b. Report an issue: GitHub.

Appendix: source

Thrown at src/Vendoring/OpenTelemetry.Instrumentation.StackExchangeRedis/Shared/Guard.cs:88

#endif
        }

        /// <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(nameof(value))] string? paramName = null)
#pragma warning disable CS8777 // Parameter must have a non-null value when exiting.
        {
#if NET
            ArgumentException.ThrowIfNullOrEmpty(value, paramName);
#else
            if (string.IsNullOrEmpty(value))
            {
                throw new ArgumentException("Must not be null or empty", paramName);
            }
#endif
        }
#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(nameof(value))] string? paramName = null)
#pragma warning disable CS8777 // Parameter must have a non-null value when exiting.
        {
#if NET
            ArgumentException.ThrowIfNullOrWhiteSpace(value, paramName);
#else

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