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);