HandyOrg/HandyControl · error · ArgumentException

The parameter must not be the default value.

Error message

The parameter must not be the default value.

What it means

Verify.IsNotDefault throws ArgumentException when a struct parameter equals its default value (e.g. 0, Guid.Empty, default(Point)). The library uses it to reject arguments that were never explicitly initialized. It is an argument-validation guard, not a state error.

Solutions

1. Initialize the struct parameter/field to a valid non-default value before calling the API.
2. Check with EqualityComparer<T>.Default.Equals(value, default) before calling and fail fast with a clearer message.
3. If the default is legitimately acceptable, the caller is using the wrong overload/API; switch to one that permits default values.

Example fix

// before
Guid id = Guid.Empty;
widget.SetId(id); // ArgumentException: The parameter must not be the default value.
// after
Guid id = Guid.NewGuid();
widget.SetId(id);

if (EqualityComparer<T>.Default.Equals(value, default(T)))
    throw new ArgumentException($"{nameof(value)} must not be the default value.", nameof(value));

static bool IsDefault<T>(T v) where T : struct => EqualityComparer<T>.Default.Equals(v, default(T));

try { api.Call(value); }
catch (ArgumentException ex) when (ex.ParamName == nameof(value)) { /* handle non-default violation */ }

When it happens

Trigger: Calling any API that internally calls Verify.IsNotDefault(value, paramName) with the C# default of that struct type, e.g. passing Guid.Empty, 0, or default(Point) where a meaningful value is required.

Common situations: Uninitialized struct fields (a Guid or handle left at its default), deserialization that skipped a field, calling a method before assigning an ID/size/handle struct member.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• The parameter must be null.
• message
• The parameter can not be either null or empty.
• The parameter can not be either null or empty or consist…
• The property cannot be null at this time.

AI-assisted analysis of HandyOrg/HandyControl@2c0875ebd6 (2026-09-14). Data as JSON: /api/errors/63bd26748a432f39. Report an issue: GitHub.

Appendix: source

Thrown at src/Shared/Microsoft.Windows.Shell/Standard/Verify.cs:59

    {
        if (value == null)
        {
            throw new ArgumentNullException(name, "The parameter can not be either null or empty or consist only of white space characters.");
        }
        if ("" == value.Trim())
        {
            throw new ArgumentException("The parameter can not be either null or empty or consist only of white space characters.", name);
        }
    }

    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    [DebuggerStepThrough]
    public static void IsNotDefault<T>(T obj, string name) where T : struct
    {
        T t = default(T);
        if (t.Equals(obj))
        {
            throw new ArgumentException("The parameter must not be the default value.", name);
        }
    }

    [DebuggerStepThrough]
    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    public static void IsNotNull<T>(T obj, string name) where T : class
    {
        if (obj == null)
        {
            throw new ArgumentNullException(name);
        }
    }

    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    [DebuggerStepThrough]
    public static void IsNull<T>(T obj, string name) where T : class
    {
        if (obj != null)

View on GitHub (pinned to 2c0875ebd6)