What causes "The property {0} cannot be null at this time." in HandyOrg/HandyControl?

Initialize the object/property before use (call the documented Initialize/Create/setup method first).

HandyOrg/HandyControl · error · InvalidOperationException

The property cannot be null at this time.

Error message

The property {0} cannot be null at this time.

What it means

Verify.PropertyIsNotNull throws InvalidOperationException when a property that must currently be initialized is still null. Unlike the argument guards, this signals the OBJECT is in the wrong state, so it uses InvalidOperationException, not ArgumentException.

Solutions

Initialize the object/property before use (call the documented Initialize/Create/setup method first).
Check the property for null before accessing dependent members and initialize lazily.
Verify construction/DI wiring so the property is actually populated.

Example fix

// before
var hwnd = window.Hwnd; // InvalidOperationException: The property Hwnd cannot be null at this time.
// after
window.EnsureInitialized();
var hwnd = window.Hwnd;

Defensive patterns

Strategy: type-guard

Validate before calling

if (obj.RequiredProperty == null)
    obj.Initialize(); // or skip usage until initialized

Type guard

static bool IsReady(T obj) => obj?.RequiredProperty != null;

Try / catch

try { UseComponent(obj); }
catch (InvalidOperationException ex) when (ex.Message.Contains("cannot be null at this time")) { obj.Initialize(); UseComponent(obj); }

Prevention

Call Initialize/Create before any member access on shell/window objects.
Check initialization order in constructors and DI wiring.
Prefer lazy initialization for properties populated late in the lifecycle.

When it happens

Trigger: Accessing a property or method on an object whose implementation calls Verify.PropertyIsNotNull(field, propertyName) while that backing field/property is still null (e.g. using a component before its Initialize/EnsureCreated ran).

Common situations: Using a control or shell object before initialization, DI/property injection that never ran, consuming a lazily-created resource before first setup, construction order bugs.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of HandyOrg/HandyControl@2c0875ebd6 (2026-09-14). Data as JSON: /api/errors/567a001fcdacbd34. Report an issue: GitHub.

Appendix: source

Thrown at src/Shared/Microsoft.Windows.Shell/Standard/Verify.cs:89

    }

    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    [DebuggerStepThrough]
    public static void IsNull<T>(T obj, string name) where T : class
    {
        if (obj != null)
        {
            throw new ArgumentException("The parameter must be null.", name);
        }
    }

    [DebuggerStepThrough]
    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    public static void PropertyIsNotNull<T>(T obj, string name) where T : class
    {
        if (obj == null)
        {
            throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, "The property {0} cannot be null at this time.", new object[]
            {
                name
            }));
        }
    }

    [DebuggerStepThrough]
    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    public static void PropertyIsNull<T>(T obj, string name) where T : class
    {
        if (obj != null)
        {
            throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, "The property {0} must be null at this time.", new object[]
            {
                name
            }));
        }
    }

View on GitHub (pinned to 2c0875ebd6)