C++ struct redefinition compiler error

I have created a new .h file with the following contents:

#include "stdafx.h"
#include <string>
using namespace std;

struct udtCharVec
{
    wstring GraphemeM3;
    wstring GraphemeM2;
};

When I want to compile it, the compiler tells me "error C2011: udtCharVec: struct type redefintion".

I did a text search, and I don't have "struct udtCharVec" defined anywhere else.

Does anybody see where I went wrong?

You are probably including this header file more than once in a single translation unit. When the file is included for the second time, struct udtCharVec has already been defined, and so you get a "type redefinition" error.

Add an include guard. After the first inclusion, CharVec_H will be defined, and so the rest of the file will be skipped:

#ifndef CharVec_H
#define CharVec_H
#include "stdafx.h"
#include <string>
using namespace std

struct udtCharVec
{
    wstring GraphemeM3;
    wstring GraphemeM2;
};
#endif

---

Say your project consisted of three files. Two header files and one source file:

CharVec.h

#include "stdafx.h"
#include <string>
using namespace std

struct udtCharVec
{
    wstring GraphemeM3;
    wstring GraphemeM2;
};

CharMatrix.h

#include "CharVec.h"
struct udtCharMatrix
{
    CharVec vec[4];
};

main.cpp

#include "CharVec.h"
#include "CharMatrix.h"

int main() {
    udtCharMatrix matrix = {};
    CharVec vec = matrix.vec[2];
};

After the preprocessor had run, main.cpp would look like this (ignoring standard library includes):

//#include "CharVec.h":
    #include "stdafx.h"
    #include <string>
    using namespace std

    struct udtCharVec //!!First definition!!
    {
        wstring GraphemeM3;
        wstring GraphemeM2;
    };
//#include "CharMatrix.h":
    //#include "CharVec.h":
        #include "stdafx.h"
        #include <string>
        using namespace std

        struct udtCharVec //!!Second definition!!
        {
            wstring GraphemeM3;
            wstring GraphemeM2;
        };
    struct udtCharMatrix
    {
        CharVec vec[4];
    };

int main() {
    udtCharMatrix matrix = {};
    CharVec vec = matrix.vec[2];
};

This expanded file include two definitions of struct udtCharVec. If you add an include guard to CharVec.h, the second definition will be removed by the preprocessor.