Original Post
I have a .CPP file that uses ostringstream class. I have included (tried both in the header file and the .CPP itself) and written "using namespace std;"(tried both in the header file and the .CPP itself). However I keep getting these two errors: E:\Projects\Engine2\V0\SimpleString.CPP(161) : error C2079: 'OStr' uses undefined class 'basic_ostringstream,class std::allocator >' E:\Projects\Engine2\V0\SimpleString.CPP(166) : error C2228: left of '.str' must have class/struct/union type What does these errors mean? How do I fix it? Thanks in advance.