Error CS1545 when using COM property from C#

Question

I have created COM interface with read/write properties:

[
    object,
    uuid(...),
    dual,
    pointer_default(unique)
]
IInterfaceWithProperty : IDispatch
{
     [propget, id(1)] HRESULT Property([out, retval] IInterface2** ppObject); 
     [propput, id(1)] HRESULT Property([in] IInterface* pObject); 
};

And when tried to use in in C#:

var value = object.Property;
object.Property = value;

got the following error:

error CS1545: Property, indexer, or event 'IInterfaceWithProperty .Property' is not supported 
by the language; try directly calling accessor methods 
'IInterfaceWithProperty.get_Property()' or 
'IInterfaceWithProperty.set_Property(IInterface)'

What could be the reason?

IInterface2 != IInterface. While that is valid in IDL, there are not a lot of languages that support this. I can't think of any. Other than C#, it allows you to work around that mistake by using the get and set accessor methods directly. Just like the error message says. — Hans Passant
– Hans Passant, Commented Sep 13, 2018 at 13:57

Nosturion · Accepted Answer · 2018-09-13 13:38:29Z

1

The reason of the error was that property should have the same type in getter and setter.

After changing IInterfaceWithProperty to

[
    object,
    uuid(...),
    dual,
    pointer_default(unique)
]
IInterfaceWithProperty : IDispatch
{
     [propget, id(1)] HRESULT Property([out, retval] IInterface2** ppObject); 
     [propput, id(1)] HRESULT Property([in] IInterface2* pObject); 
};

the problem disappeared.

answered Sep 13, 2018 at 13:38

Nosturion

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