解压压缩富文本字段

我有一个包含压缩RichText数据的数据表中的图像列。我想这是从Outlook (PR_RTF_COMPRESSED属性或其他东西)获得的。我需要把它解压。使用c#，我正在尝试以下内容，但我得到一个System.Runtime.InteropServices.COMExceptions，无法找出它。

我发现一些旧的链接问这个问题，没有解决的答案。下面是我使用c#编写的代码片段。

 public Form1()
    {
        InitializeComponent();
        IStream streamOut;
        string con = "connection string";
        SqlCommand command = new SqlCommand("select top 10 columnInCompressedRichTextFormat FROM tableWithCompressedRichTextData", new SqlConnection(dbConnectionString));
        DataTable x = new DataTable();
        SqlDataAdapter a = new SqlDataAdapter(command);
        a.Fill(x);
        a.Dispose();
        foreach (DataRow r in dtResults.Rows)
        {
            byte[] arrayOfBytes = (byte[]) r["columnInCompressedRichTextFormat"];
            IStream i = CreateIStreamFromBytes(arrayOfBytes);
            WrapCompressedRTFStream(input, 0, out streamOut);
        }
    }
    public IStream CreateIStreamFromBytes(byte[] bytes)
    {
        IntPtr hglobal = Marshal.AllocHGlobal(bytes.Length);
        Marshal.Copy(bytes, 0, hglobal, bytes.Length);
        IStream stream = null;
        CreateStreamOnHGlobal(hglobal, true, out stream);
        return stream;
    }
    [DllImport("Mapi32.dll", PreserveSig = false)]
    private static extern void
        WrapCompressedRTFStream(
        [MarshalAs(UnmanagedType.Interface)] IStream lpCompressedRTFStream,
        uint ulflags,
        [MarshalAs(UnmanagedType.Interface)] out IStream lpUncompressedRTFStream
        );
    [DllImport("ole32.dll", PreserveSig = false)]
    static extern int CreateStreamOnHGlobal(IntPtr hGlobal,
        [MarshalAs(UnmanagedType.Bool)] bool fDeleteOnRelease,
        [MarshalAs(UnmanagedType.Interface)] out IStream ppstm
        );
    public const uint MAPI_MODIFY = 0x00000001;
    public const uint STORE_UNCOMPRESSED_RTF = 0x00008000;
}

WrapCompressedRTFStream抛出错误。什么好主意吗?

许多谢谢。