how to declare public class

Question

I am so sorry for the question that sounds so stupid :)

I have such line of code:

namespace Messages{
/// @brief Interface to support building a message during decoding.
class ValueMessageBuilder : public Common::Logger
....

And I can not use ValueMessageBuilder from my c# project because of this error:

Cannot access internal struct 'ValueMessageBuilder' here.

So I've tried to make it public and recompile dll:

public class ValueMessageBuilder : public Common::Logger

But compilation failed with such error Error C3381: 'QuickFAST::Messages::ValueMessageBuilder' : assembly access specifiers are only available in code compiled with a /clr option F:\Oleg\quickfast_1_4_0_my\src\Messages\ValueMessageBuilder.h 17 1 QuickF‌AST

So the question is how to convert internal ValueMessageBuilder structure to public?

Possibly this question asked on SO previously may help: http://stackoverflow.com/questions/920844/c-sharp-how-to-access-internal-class-from-external-assembly — Paul McCabe, Apr 29 '12 at 14:41

score 0 · Answer 1 · answered Apr 29 '12 at 14:51

0

As the error states your code must be compiled with /clr option (Project properties | General | Common Language Runtime Support). after that your project will become c++/clr (managed c++). Also I think the class should be preceded with ref keyword to be visible in c#.

answered Apr 29 '12 at 14:51

Mohammad

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`/clr` is alredy set, and `ref` keyword doesn't work (see comment above) – Oleg Vazhnev Apr 29 '12 at 15:29

score 0 · Answer 2 · edited Apr 13 '17 at 12:40

0

For a class to be usable from C#, it needs to be a managed type with .NET metadata.

Use either ref class or value class.

Note that an object can't contain both managed and native class types. However, a native class can hold a handle to a managed instance (use gcroot) and a managed type can hold a pointer to a native object (My smart pointer, posted on codereview, may help with lifetime management).

edited Apr 13 '17 at 12:40

Community

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answered Apr 29 '12 at 14:59

Ben Voigt

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using `ref class` or `value class` i receive `this declaration has no storage class or type specified` error – Oleg Vazhnev Apr 29 '12 at 15:27
@javapowered: It sounds like `/clr` isn't set on every single file that includes this header. – Ben Voigt Apr 29 '12 at 15:34
but i see `/clr` option in project properties, I don't know what else can I do... – Oleg Vazhnev Apr 29 '12 at 15:45
@javapowered: There's compile options for the project, and also compile options for each individual compilation unit (same properties window, access it from the `.cpp` file). – Ben Voigt Apr 29 '12 at 15:46
it wouldn't be easy to check every possible file in the project – Oleg Vazhnev Apr 29 '12 at 16:32
@javapowered: Start by checking the one being compiled when the error happens. (Not the header, the .cpp that included it) – Ben Voigt Apr 29 '12 at 16:51

how to declare public class

2 Answers2