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IDispatch::Invoke

  • Статья

This method provides access to properties and methods exposed by an object.

HRESULT Invoke( 
  DISPID dispIdMember, 
  REFIID riid, 
  LCID lcid, 
  WORD wFlags, 
  DISPPARAMS FAR* pDispParams, 
  VARIANT FAR* pVarResult, 
  EXCEPINFO FAR* pExcepInfo, 
  unsigned int FAR* puArgErr 
);

Parameters

  • dispIdMember
    [in] Identifies the member. Use IDispatch::GetIDsOfNames or the object's documentation to obtain the dispatch identifier.

  • riid
    [in] Reserved for future use; set to IID_NULL.

  • lcid
    [in] Locale context in which to interpret parameters. The lcid is used by the GetIDsOfNames function, and is also passed to Invoke to allow the object to interpret its parameters specific to a locale.

    Applications that do not support multiple national languages can ignore this parameter.

  • wFlags
    [in] Flags describing the context of the Invoke call. It is one of the following values.

    Value Description
    DISPATCH_METHOD The member is invoked as a method. If a property has the same name, both this and the DISPATCH_PROPERTYGET flag may be set.
    DISPATCH_PROPERTYGET The member is retrieved as a property or data member.
    DISPATCH_PROPERTYPUT The member is changed as a property or data member.
    DISPATCH_PROPERTYPUTREF The member is changed by a reference assignment, rather than a value assignment. This flag is valid only when the property accepts a reference to an object.

  • pDispParams
    [in, out] Pointer to a structure that contains an array of parameters, an array of parameter DISPIDs for named parameters, and counts for the number of elements in the arrays. See the Remarks section that follows for a description of the DISPPARAMS structure.

  • pVarResult
    [out] Pointer to the location where the result is to be stored, or NULL if the caller expects no result. This parameter is ignored if DISPATCH_PROPERTYPUT or DISPATCH_PROPERTYPUTREF is specified.

  • pExcepInfo
    [out] Pointer to a structure that contains exception information. This structure should be filled in if DISP_E_EXCEPTION is returned. Can be NULL.

  • puArgErr
    [out] The index within rgvarg of the first parameter that has an error. Arguments are stored in pDispParams->rgvarg in reverse order, so the first parameter is the one with the highest index in the array. This parameter is returned only when the resulting return value is DISP_E_TYPEMISMATCH or DISP_E_PARAMNOTFOUND. For details, see Returning Errors.

Return Values

The following table shows the return values for this function.

Value Description
S_OK Success.
DISP_E_BADPARAMCOUNT The number of elements provided to DISPPARAMS is different from the number of parameters accepted by the method or property.
DISP_E_BADVARTYPE One of the parameters in rgvarg is not a valid variant type.
DISP_E_EXCEPTION The application needs to raise an exception. In this case, the structure passed in pExcepInfo should be filled in.
DISP_E_MEMBERNOTFOUND The requested member does not exist, or the call to Invoke tried to set the value of a read-only property.
DISP_E_NONAMEDARGS This implementation of IDispatch does not support named parameters.
DISP_E_OVERFLOW One of the parameters in rgvarg could not be coerced to the specified type.
DISP_E_PARAMNOTFOUND One of the parameter DISPIDs does not correspond to a parameter on the method. In this case, puArgErr should be set to the first parameter that contains the error.
DISP_E_TYPEMISMATCH One or more of the parameters could not be coerced. The index within rgvarg of the first parameter with the incorrect type is returned in the puArgErr parameter.
DISP_E_UNKNOWNINTERFACE The interface identifier passed in riid is not IID_NULL.
DISP_E_UNKNOWNLCID The member being invoked interprets string parameters according to the LCID, and the LCID is not recognized. If the LCID is not needed to interpret parameters, this error should not be returned.
DISP_E_PARAMNOTOPTIONAL A required parameter was omitted.

In 16-bit versions, you can define your own errors using the MAKE_SCODE value macro.

Remarks

Generally, you should not implement Invoke directly. Instead, use the dispatch interface create functions CreateStdDispatch and DispInvoke.

If some application-specific processing needs to be performed before calling a member, the code should perform the necessary actions, and then call ITypeInfo::Invoke to invoke the member. ITypeInfo::Invoke acts exactly like IDispatch::Invoke. The standard implementations of IDispatch::Invoke created by CreateStdDispatch and DispInvoke defer to ITypeInfo::Invoke.

In an ActiveX client, IDispatch::Invoke should be used to get and set the values of properties, or to call a method of an ActiveX object. The dispIdMember parameter identifies the member to invoke. The DISPIDs that identify members are defined by the implementor of the object and can be determined by using the object's documentation, the GetIDsOfNames function, or the ITypeInfo interface.

The information that follows addresses developers of ActiveX clients and others who use code to expose ActiveX objects. It describes the behavior that users of exposed objects should expect.

Requirements

OS Versions: Windows CE 2.0 and later.
Header: Oaidl.h, Oaidl.idl.
Link Library: Oleaut32.lib, Uuid.lib.

See Also

IDispatch | DISPPARAMS | IDispatch::GetIDsOfNames | IDispatch::Invoke | ITypeInfo | ITypeInfo::Invoke | dispinterface

Last updated on Wednesday, April 13, 2005

© 2005 Microsoft Corporation. All rights reserved.