dual.md

description	title	ms.date	f1_keywords	helpviewer_keywords	ms.assetid
Learn more about: dual	dual (C++ COM Attribute)	10/02/2018	vc-attr.dual	dual attribute	5d4a9069-d819-42cd-ba56-bbcda17157d9

dual

Places an interface in the .idl file as a dual interface.

Syntax

[dual]

Remarks

When the dual C++ attribute precedes an interface, it causes the interface to be placed inside the library block in the generated .idl file.

Example

The following code is an attribute block that uses dual before an interface definition:

// cpp_attr_ref_dual.cpp
// compile with: /LD
#include <windows.h>
[module(name="MyLibrary")];

[uuid("2F5F63F1-16DA-11d2-9E7B-00C04FB926DA"), dual]

__interface IStatic : IDispatch
{
   HRESULT Func1(int i);
   [   propget,    id(1),    bindable,    displaybind,    defaultbind,    requestedit
   ]
   HRESULT P1([out, retval] long *nSize);
   [   propput,    id(1),    bindable,    displaybind,    defaultbind,    requestedit
   ]
   HRESULT P1([in] long nSize);
};

[cpp_quote("#include file.h")];

Requirements

Attribute context	Value
Applies to	interface
Repeatable	No
Required attributes	None
Invalid attributes	dispinterface

For more information, see Attribute Contexts.

See also

IDL Attributes
Attributes by Usage
custom
dispinterface
object
__interface