What does HRESULT 0x8002000F (DISP_E_PARAMNOTOPTIONAL) mean?

DISP_E_PARAMNOTOPTIONAL

Required Automation parameter was omitted

DISP_E_PARAMNOTOPTIONAL is HRESULT 2147614735 (0x8002000F) from winerror.h. AllStat describes it as “Parameter not optional.” The value must be interpreted at IDispatch invocation of a member with mandatory and optional parameters, because the same high-level symptom can come from a different contract boundary and require different cleanup.

The decisive interpretation for DISP_E_PARAMNOTOPTIONAL is that a parameter declared as required has no supplied value after positional and named argument binding. Treat DISP_E_PARAMNOTOPTIONAL as a contract result from its owning subsystem and retain the unmodified HRESULT in logs and test assertions.

Where the result appears

• DISP_E_PARAMNOTOPTIONAL is returned while Automation binds or executes IDispatch invocation of a member with mandatory and optional parameters.
• For DISP_E_PARAMNOTOPTIONAL, retain the member name and DISPID, invocation flags, LCID, cArgs, cNamedArgs, and the exact VARIANTARG sequence in reverse Automation order.
• The output contract for DISP_E_PARAMNOTOPTIONAL includes puArgErr, EXCEPINFO, result VARIANT, by-reference values, and SAFEARRAY lock or ownership state; inspect them before cleanup.

Map DISP_E_PARAMNOTOPTIONAL to one concrete invocation and one concrete object or metadata identity before interpreting the human-readable description.

Typical causes and interpretation boundary

Common cause categories for DISP_E_PARAMNOTOPTIONAL are: the caller assumes a parameter is optional; bindings are stale; a named argument was misspelled and therefore not bound. For DISP_E_PARAMNOTOPTIONAL, the evidence should distinguish configuration, lifetime, input, identity, resource, and version failures rather than grouping them.

The check that separates DISP_E_PARAMNOTOPTIONAL from nearby HRESULTs is: a parameter declared as required has no supplied value after positional and named argument binding. The text of DISP_E_PARAMNOTOPTIONAL narrows the search, but the owning API state must confirm the condition before automation changes the system.

Evidence and telemetry

• Record DISP_E_PARAMNOTOPTIONAL with the object CLSID or ProgID, interface identity, member DISPID, dispatch flags, and type-library version.
• For DISP_E_PARAMNOTOPTIONAL, capture member signature; missing parameter position or DISPID; cArgs; optional flags; versioned type library.
• Log VARIANT type tags, dimensions, bounds, lengths, and null/empty distinctions for DISP_E_PARAMNOTOPTIONAL, but redact actual confidential argument values.
• Preserve the caller language/runtime, generated interop version, LCID, and whether the call crossed a process boundary when DISP_E_PARAMNOTOPTIONAL occurs.
• After DISP_E_PARAMNOTOPTIONAL, call VariantClear, SysFreeString, SafeArrayDestroy, or release interfaces only for values whose ownership was transferred by the documented contract.

For privacy-safe diagnosis of DISP_E_PARAMNOTOPTIONAL, capture the call schema and state transitions but hash or omit confidential payloads.

Diagnostic sequence

• Capture DISP_E_PARAMNOTOPTIONAL (0x8002000F) at IDispatch::GetIDsOfNames or IDispatch::Invoke before the language runtime converts it to a script exception.
• For <code>DISP_E_PARAMNOTOPTIONAL</code>, resolve the deployed member signature from ITypeInfo and compare its DISPIDs, parameter flags, VARTYPEs, optional values, and property-put rules with the caller.
• Prove the decisive condition for DISP_E_PARAMNOTOPTIONAL: a parameter declared as required has no supplied value after positional and named argument binding.
• Inspect the likely binding or representation causes for DISP_E_PARAMNOTOPTIONAL: the caller assumes a parameter is optional; bindings are stale; a named argument was misspelled and therefore not bound.
• Reconstruct DISPPARAMS exactly, including reverse positional ordering and named argument placement, then reproduce DISP_E_PARAMNOTOPTIONAL with the smallest value set.
• Verify the result VARIANT, EXCEPINFO, puArgErr, by-reference arguments, SAFEARRAY lock count, and object state after DISP_E_PARAMNOTOPTIONAL before deciding on retry.

Correct handling and recovery

For DISP_E_PARAMNOTOPTIONAL, the appropriate recovery is to supply the required value in the correct reverse-order layout, regenerate wrappers from the deployed type library, and avoid inventing defaults. Recovery from DISP_E_PARAMNOTOPTIONAL should name the component responsible for retry and the evidence that makes another attempt safe.

The failure path for DISP_E_PARAMNOTOPTIONAL should leave outputs in a known state and avoid double release, double commit, or reuse of stale pointers.

Practical scenario

A report method gained a required output-format parameter; an old wrapper is regenerated and supplies the explicit format.

To prevent recurrence of DISP_E_PARAMNOTOPTIONAL, preserve a minimal fixture that asserts both the failing condition and the state after recovery.

Difference from related HRESULTs

DISP_E_PARAMNOTFOUND says a named identifier cannot be resolved; DISP_E_PARAMNOTOPTIONAL says a known required slot has no value.

Classify DISP_E_PARAMNOTOPTIONAL by the stated contract difference, since severity bits alone do not determine the correct response.

Developer and administrator guidance

Automation adapters should handle DISP_E_PARAMNOTOPTIONAL at the dispatch boundary and expose the member, parameter, and type information needed to repair the call. A generic retry after <code>DISP_E_PARAMNOTOPTIONAL</code> with unchanged DISPPARAMS usually repeats the same deterministic binding error.

For DISP_E_PARAMNOTOPTIONAL, deployment owners should compare the registered type library and server binary as one versioned unit. After <code>DISP_E_PARAMNOTOPTIONAL</code>, re-registering arbitrary DLLs or changing locale system-wide is inappropriate unless the captured metadata proves registration or LCID drift.

References

• Microsoft: VARIANT structure — official Microsoft documentation relevant to DISP_E_PARAMNOTOPTIONAL.
• Microsoft: VariantClear — official Microsoft documentation relevant to DISP_E_PARAMNOTOPTIONAL.
• Microsoft: IDispatch::Invoke — official Microsoft documentation relevant to DISP_E_PARAMNOTOPTIONAL.
• Microsoft: HRESULT values — official Microsoft documentation relevant to DISP_E_PARAMNOTOPTIONAL.

Looking for a different code? Search another status or error code.