Template class in Managed C++

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.