Marshalling problem in Managed C++ Wrapper

Doing Managed C++ Wrapper in VS2008. Have a native defined data structure as follows:

Code:

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class API TF_StringList
{
public:
  TF_StringList(const char* encoding = "cp_1252");
   
  ~TF_StringList();

  TF_String* first_string() const {return start_string;}
  TF_String* last_string() const {return end_string;}

  void insert(const TF_String& aString);
  void insert(const char* aString); 

  // If the length parameter is larger than the size of the string,
  // The behavior is uncertain.
  void insert(const tf_Byte* aString, size_t aByteLength);

  void clear();

  size_t size() const { return list_size; }

  char* character_encoding;

private:
 
  void set_first(TF_String* stringPtr) {start_string = stringPtr;}
  void set_last (TF_String* stringPtr) {end_string = stringPtr;}

  TF_String* start_string;
  TF_String* end_string;
  TF_String* curr_pos;
  size_t list_size;


  // Do not expose the copy constructor and the assignment operator.
  TF_StringList(const TF_StringList& tmp);
  TF_StringList& operator=(const TF_StringList& tmp);

};

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In one of my managed functions I have parameter of List<String^> categoryList and I want to load an object of type TF_StringList with the elements of that parameter.

Code:

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//Instantiate the TF_StringList
categories = new TF_StringList();
for(int i=0; i<categoryList.Count; i++)
{
  const char* str = (const char*)(Marshal::StringToHGlobalAnsi(categoryList[i])).ToPointer();
  categories->insert(str);
}

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On the last line, I get the error:C2663: 'TF_StringList::insert' : 3 overloads have no legal conversion for 'this' pointer
First, The error would lead me to believe that str is not "seen" by the TF_StringList instance as a const char* since the insert(const char* aString) does not accept it.

Second, the list does not index out a Managed String (e.g. that String^ st = categoryList[i] is not valid). This seems unlikely since the declaration is List categoryList.

How can I check to find out what the problem actually is?

C2663 is about const. What is categories variable declaratin? Please post the whole function.

The complete function so far is:

Code:

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TFWrapper::TFWrapper(String^ mlexDir, String^ mlic, String^ mkey, List<String^> categoryList, Boolean^ m_useConj, String^ m_lang, String^ m_encoding)
{
        const char* c_lexDir = (char*)(Marshal::StringToHGlobalAnsi(mlexDir)).ToPointer();
        const char* c_lic = (char*)(Marshal::StringToHGlobalAnsi(mlic)).ToPointer();
        const char* c_key = (char*)(Marshal::StringToHGlobalAnsi(mkey)).ToPointer();
        finder = new TF_Finder(c_lexDir, c_lic, c_key);
        catalog = new TF_NameCatalog();
        categories = new TF_StringList();
        for(int i=0; i<categoryList.Count; i++)
        {
            const char* str = (const char*)(Marshal::StringToHGlobalAnsi(categoryList[i])).ToPointer();
            categories->insert(str);
        }
        customEntities = new TF_StringList();
        c_useConj = (bool*)Convert::ToBoolean(m_useConj);
}

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Have read where the proper declaration for a parameter of a List of Managed Strings is

Code:

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List<String^>^% categoryList

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when I index into the list for an item, apparently the return is a String pointer:

Code:

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String * mstr = categoryList[i];

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Since I'm trying to make it acceptable to the insert method in the unmanaged dll:
Create the unmanaged class:

Code:

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TF_StringList * categories = new TF_StringList();

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Then convert mstr to a const char*

Code:

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const char* str = (char*)(*void)Marshal::StringToHGlobalAnsi(mstr);

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then pass str to the categories->insert(const char*);
Still get C2663 error

The problem here was that I had declared the List instance as const. The error is thrown because I'm trying to change a const object by inserting into it.

Code:

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String * mstr = categoryList[i];
const char* str = (char*)(*void)Marshal::StringToHGlobalAnsi(mstr);

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Doesn't it should be:

Code:

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const char* str = (char*)(*void)Marshal::StringToHGlobalAnsi(*mstr);

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