What does HRESULT 0x8002000E (DISP_E_BADPARAMCOUNT) mean?

DISP_E_BADPARAMCOUNT

Automation member received the wrong number of arguments

DISP_E_BADPARAMCOUNT is HRESULT 2147614734 (0x8002000E) from winerror.h. AllStat describes it as “Invalid number of parameters.” The value must be interpreted at IDispatch::Invoke binding positional and named values to a member signature, because the same high-level symptom can come from a different contract boundary and require different cleanup.

The decisive interpretation for DISP_E_BADPARAMCOUNT is that cArgs and cNamedArgs cannot satisfy the selected method or property invocation form. The operational record for DISP_E_BADPARAMCOUNT needs the native value, symbolic constant, component build, and call phase; the message alone is insufficient.

Where the result appears

• DISP_E_BADPARAMCOUNT is returned while Automation binds or executes IDispatch::Invoke binding positional and named values to a member signature.
• For DISP_E_BADPARAMCOUNT, 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_BADPARAMCOUNT includes puArgErr, EXCEPINFO, result VARIANT, by-reference values, and SAFEARRAY lock or ownership state; inspect them before cleanup.

For DISP_E_BADPARAMCOUNT, separate caller state from runtime and server state first; otherwise cleanup and retry may target the wrong generation of the operation.

Typical causes and interpretation boundary

Common cause categories for DISP_E_BADPARAMCOUNT are: an optional argument is omitted incorrectly; property put lacks DISPID_PROPERTYPUT; generated bindings target another version; arguments are doubled. Each possible cause of DISP_E_BADPARAMCOUNT predicts different outputs and recovery behavior, which should be verified explicitly.

The check that separates DISP_E_BADPARAMCOUNT from nearby HRESULTs is: cArgs and cNamedArgs cannot satisfy the selected method or property invocation form. Without proof of the distinguishing condition for DISP_E_BADPARAMCOUNT, the safest action is to preserve evidence and refrain from destructive cleanup.

Evidence and telemetry

• Record DISP_E_BADPARAMCOUNT with the object CLSID or ProgID, interface identity, member DISPID, dispatch flags, and type-library version.
• For DISP_E_BADPARAMCOUNT, capture member DISPID and invoke flags; actual counts; optional parameters; property-put named DISPID; type-library signature.
• Log VARIANT type tags, dimensions, bounds, lengths, and null/empty distinctions for DISP_E_BADPARAMCOUNT, 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_BADPARAMCOUNT occurs.
• After DISP_E_BADPARAMCOUNT, call VariantClear, SysFreeString, SafeArrayDestroy, or release interfaces only for values whose ownership was transferred by the documented contract.

A useful DISP_E_BADPARAMCOUNT event contains ownership and shape information, not raw documents, passwords, access tokens, or full Automation values.

Diagnostic sequence

• Capture DISP_E_BADPARAMCOUNT (0x8002000E) at IDispatch::GetIDsOfNames or IDispatch::Invoke before the language runtime converts it to a script exception.
• For <code>DISP_E_BADPARAMCOUNT</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_BADPARAMCOUNT: cArgs and cNamedArgs cannot satisfy the selected method or property invocation form.
• Inspect the likely binding or representation causes for DISP_E_BADPARAMCOUNT: an optional argument is omitted incorrectly; property put lacks DISPID_PROPERTYPUT; generated bindings target another version; arguments are doubled.
• Reconstruct DISPPARAMS exactly, including reverse positional ordering and named argument placement, then reproduce DISP_E_BADPARAMCOUNT with the smallest value set.
• Verify the result VARIANT, EXCEPINFO, puArgErr, by-reference arguments, SAFEARRAY lock count, and object state after DISP_E_BADPARAMCOUNT before deciding on retry.

Correct handling and recovery

For DISP_E_BADPARAMCOUNT, the appropriate recovery is to derive the signature from current type information, include required property named arguments, and encode omitted optionals using the documented VARIANT form. For DISP_E_BADPARAMCOUNT, repeat the operation only after the failed condition has changed and the caller can distinguish a duplicate effect.

When DISP_E_BADPARAMCOUNT is returned, use the documented output contract and reconcile remote or persistent effects before replaying the request.

Practical scenario

A property assignment passes one value but omits the required named DISPID_PROPERTYPUT, so the invoker corrects DISPPARAMS.

An automated test for DISP_E_BADPARAMCOUNT should verify raw HRESULT, output ownership, cleanup behavior, and the absence of an unsafe automatic retry.

Difference from related HRESULTs

DISP_E_PARAMNOTOPTIONAL identifies a specific missing required parameter; DISP_E_BADPARAMCOUNT is the overall count mismatch.

The comparison matters operationally for DISP_E_BADPARAMCOUNT: one result may permit fallback while the other requires repair, cancellation, or state reconciliation.

Developer and administrator guidance

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

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

References

• Microsoft: EXCEPINFO — official Microsoft documentation relevant to DISP_E_BADPARAMCOUNT.
• Microsoft: VARIANT structure — official Microsoft documentation relevant to DISP_E_BADPARAMCOUNT.
• Microsoft: HRESULT values — official Microsoft documentation relevant to DISP_E_BADPARAMCOUNT.

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