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Prohibits assignment to a data member.


Attribute Context

Applies to Interface method
Repeatable No
Required attributes None
Invalid attributes None

For more information about the attribute contexts, see Attribute Contexts.


The readonly C++ attribute has the same functionality as the readonly MIDL attribute.

If you want to prohibit modification of a method parameter, then use the in attribute.


The following code shows a use of the readonly attribute:

// cpp_attr_ref_readonly.cpp
// compile with: /LD
[idl_quote("midl_pragma warning(disable:2461)")];
#include "unknwn.h"

[dispinterface, uuid(11111111-1111-1111-1111-111111111111)]
__interface IFireTabCtrl
   [readonly, id(1)] int i();

See Also

IDL Attributes | Data Member Attributes | Attributes Samples