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I have problem using template class in a managed C++ dll. I got error C2065:

'MyTempateCall' : undeclared identifier. I don't have problme use un-template

class.

Below is the simple example it has the same problem as my real project.



// The dll library

#pragma once

using namespace System;

namespace TestDll {



public ref class Class3

{

};



template<class T>

public ref class Class2

{

public:

Class2<T>(T theValue)

{

myValue = theValue;

}



private:

T myValue;

};



template ref class Class2<int>;

template ref class Class2<double>;





public ref class TestClassInSameNameSpace

{

void Test()

{

Class2<int>class2(60);

}



private:

Class3 class3;

};

}



// The Other application that uses the privious dll. Now I got this error:

error

// C2065: 'Class2' : undeclared identifier. It is fine with Class3.

#pragma once

using namespace System;

using namespace TestDll;



namespace CallTestDLL {



public ref class TestClass

{

void Test()

{

Class2<int>class2(60);

}



private:

Class3 class3;

};

}



I add the dll as the reference. I got same error message if I add the

library project as the reference.

What did I miss?

Thank you for any help.


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Haiping wrote:

Templates can't be exported over dll boundaries easily, it's rather

tricky to do it and only with the restriction to export defined template

specializations.



Why don't you use generics ? At least for this "simple" case it's simple

to replace the template class by a generic one.



E.g. rewrite your example as:



generic<typename T>

public ref class Class2

{

public:

Class2<T>(T theValue)

{

myValue = theValue;

}



private:

T myValue;

};





And you can use this class not only from C++, but any .NET 2.0

compatible language.

The "downside" is that not all C++ template classes can be replaced by

generic ones. But if you want to export generic classes, IMHO generics

are the best way to go.



Hope this helps,

Andre

-

Hi Andre,



This is just a example. In our realy project the Class2 is also derive from

a native C++ template class. So it cannot be generic.



I solved the problem by use the dependencies instead of reference, and also

include the .h and .cpp files.



Thanks for your response,

Haiping



-

Haiping wrote:

Hm, but Class2 is a ref class, a managed one. If I haven't missed

something, managed classes cannot (yet) derive from native ones and vice

versa.

So I wonder how you accomplished that ?





Then you don't need a dll at all ;-)



:-) Your welcome. Though it didn't help that much. But you found a

solution of

your own.



Regards,

Andre





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