打开窗口进行选择文件（txt文件），打开所选文件，读入文件

用mfc编写项目的时候往往需要调用窗口，允许用户通过窗口进行选择文件操作

    TCHAR szBuffer[MAX_PATH] = { 0 };

    OPENFILENAME ofn = { 0 };

    ofn.lStructSize = sizeof(ofn);

    ofn.hwndOwner = m_hWnd;

    ofn.lpstrFilter = _T("txt文件(*.txt)\0");//要选择的文件后缀

    char buf[80];

    getcwd(buf, sizeof(buf));

    ofn.lpstrInitialDir = _T(buf);//默认的文件路径

    ofn.lpstrFile = szBuffer;//szBuffer是存放的选择的文件路径

    ofn.nMaxFile = sizeof(szBuffer) / sizeof(*szBuffer);

    ofn.nFilterIndex = 0;

    ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST | OFN_EXPLORER;
    //标志如果是多选要加上OFN_ALLOWMULTISELECT

    BOOL bSel;

    bSel = GetOpenFileName(&ofn);//实际打开窗口的语句

    int i = 0,l=0;

    int len = strlen(szBuffer) ;

    TCHAR filename[MAX_PATH];

    //路径变换，变换为..\\..\\...

    while (i < len) {

        filename[l++] = szBuffer[i];

        if (szBuffer[i++] == '\\')

            filename[l++] = '\\';

    }

    filename[l++] = '\0';

    FILE *fp;

    if ((fp = fopen(filename, "r")) == NULL)

    {

        printf("无法打开此文件\n");

        return;

    }

    char *miwen = new char[1024];

    i = 0;

    while (!feof(fp)) {

        miwen[i++] = fgetc(fp);

    }

    miwen[i - 1] = '\0';

    fclose(fp);