I am using Visual C++ CFile.

I open a file, write some data, then read some data, must I flush the data between the write and read operations:

    CFile File;
    CByteArray Buf1, Buf2;

    Buf1.SetSize(512);
    memset(Buf1.GetData(), 1, Buf1.GetSize());

    Buf2.SetSize(512);
    memset(Buf2.GetData(), 0, Buf2.GetSize());

    if (File.Open(_T("E:\Temp\1.dat"), CFile::modeCreate | CFile::modeReadWrite | CFile::shareDenyNone))
    {
        File.Seek(0, CFile::begin);
        File.Write(Buf1.GetData(), Buf1.GetSize());

        //  Need I flush the data before starting the read
        //  File.Flush();

        File.Seek(0, CFile::begin);
        File.Read(Buf2.GetData(), Buf2.GetSize());

        if (memcmp(Buf1.GetData(), Buf2.GetData(), Buf1.GetSize()) == 0)
            AfxMessageBox(_T("Same"));
    }

It seems without the flush, the read data is also same as the written data.