C++ CLI gcnew undeclared identifier-Collection of common programming errors

String* response_Page="";
std::string http_Response;

//WinHttp Request
//http_Response append (pszOutBuffer);

response_Page = gcnew System::String(respstring);

I am trying to create a managed C++/CLI dll to be used in c#, new to C++, it is really complex, cant get much info just by searching.

Update: I am using Common Language Runtime Support, Old Syntax (/clr:oldSyntax)

Getting error: error C2065: ‘gcnew’ : undeclared identifier