What causes "{parameterName} can not be null!" in abpframework/abp?

abpframework/abp · error · ArgumentException

{parameterName} can not be null!

Error message

{parameterName} can not be null!

What it means

The string overload of Check.NotNull validates that a string is non-null and within optional maxLength/minLength bounds (defaults: maxLength=int.MaxValue, minLength=0). This overload deliberately throws ArgumentException (not ArgumentNullException) with a human-readable message; it differs from the generic Check.NotNull<T> which throws ArgumentNullException. It is ABP's standard pre-condition guard used pervasively across the framework.

Source

Thrown at framework/src/Volo.Abp.Core/Volo/Abp/Check.cs:47

    {
        if (value == null)
        {
            throw new ArgumentNullException(parameterName, message);
        }

        return value;
    }

    [ContractAnnotation("value:null => halt")]
    public static string NotNull(
        [System.Diagnostics.CodeAnalysis.NotNull] string? value,
        [InvokerParameterName][NotNull] string parameterName,
        int maxLength = int.MaxValue,
        int minLength = 0)
    {
        if (value == null)
        {
            throw new ArgumentException($"{parameterName} can not be null!", parameterName);
        }

        if (value.Length > maxLength)
        {
            throw new ArgumentException($"{parameterName} length must be equal to or lower than {maxLength}!", parameterName);
        }

        if (minLength > 0 && value.Length < minLength)
        {
            throw new ArgumentException($"{parameterName} length must be equal to or bigger than {minLength}!", parameterName);
        }

        return value;
    }

    [ContractAnnotation("value:null => halt")]
    public static string NotNullOrWhiteSpace(
        [System.Diagnostics.CodeAnalysis.NotNull] string? value,

View on GitHub (pinned to 7ed43b1931)

Solutions

Pass a non-null string.
If the value may legitimately be absent, resolve to a default (e.g. string.Empty) at the caller before invoking the guarded API.
Trace the parameter name in the message back to the offending argument.

Example fix

// before
Check.NotNull(maybeNull, nameof(maybeNull));

// after
Check.NotNull(maybeNull ?? string.Empty, nameof(maybeNull));

Defensive patterns

Strategy: validation

Validate before calling

if (value is null) throw new ArgumentNullException(nameof(value));
// or resolve to a default before the guarded call:
Check.NotNull(value ?? string.Empty, nameof(value));

Type guard

bool IsPresent(string? s) => s is not null;

Prevention

Coalesce optional strings to a default at the caller before invoking guarded ABP APIs.
Enable nullable reference types so the compiler warns on null propagation.
Trace the parameter name in the message back to the offending argument.

When it happens

Trigger: Check.NotNull(someString, nameof(someString)) when someString is null; equivalently an ABP internal call guarding a string parameter receives null.

Common situations: Passing null where a required string (name, key, connection string) is expected; a config value resolved to null and forwarded into an ABP API.

Related errors

AI-assisted analysis of abpframework/abp@7ed43b1931 (2026-08-13). Data as JSON: /api/errors/3c8957b3341f8898. Report an issue: GitHub.