C# Signature:

[DllImport("ole32.dll")]
static extern int StgOpenStorageEx([MarshalAs(UnmanagedType.LPWStr)] string
   pwcsName, uint grfMode, uint stgfmt, uint grfAttrs, ref STGOPTIONS
   pStgOptions, IntPtr reserved2, [In] ref Guid riid,
   [MarshalAs(UnmanagedType.IUnknown)] out object ppObjectOpen);

User-Defined Types:

None.

Notes:

None.

Tips & Tricks:

Please add some!

Sample Code:

Please add some!

Alternative Managed API:

The System.IO.Packaging namespace contains public StorageInfo and StreamInfo classes that encapsulate OLE structured storage access. Unfortunately, the StorageRoot class, which is needed to create or open the files, is an internal class. However, you can use reflection to access the methods on StorageRoot if necessary. The code below will open a storage file and convert it to XML where each stream is hex encoded.

    public static void ReadOSSFile(string fileName, XmlWriter writer)
    {
        int checkResult = StgIsStorageFile(fileName);
        Preconditions.RequireArgument(checkResult == 0,
            "The specified file is not an OLE Structured Storage file.");

        StorageInfo storageRoot = GetStorageRoot(fileName);
        try
        {
            WriteStorage(storageRoot, fileName, writer);
        }
        finally
        {
            CloseStorageRoot(storageRoot);
        }
    }

    private static StorageInfo GetStorageRoot(string fileName)
    {
        StorageInfo storageRoot = (StorageInfo)InvokeStorageRootMethod(null,
            "Open", fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
        if (storageRoot == null)
        {
            Utilities.ThrowInvalidStateFmt("Unable to open \"{0}\" as a structured storage file.", fileName);
        }
        return storageRoot;
    }

    private static void CloseStorageRoot(StorageInfo storageRoot)
    {
        InvokeStorageRootMethod(storageRoot, "Close");
    }

    private static object InvokeStorageRootMethod(StorageInfo storageRoot, string methodName, params object[] methodArgs)
    {
        //We need the StorageRoot class to directly open an OSS file.  Unfortunately, it's internal.
        //So we'll have to use Reflection to access it.  This code was inspired by:
        //http://henbo.spaces.live.com/blog/cns!2E073207A544E12!200.entry
        //Note: In early WinFX CTPs the StorageRoot class was public because it was documented
        //here: http://msdn2.microsoft.com/en-us/library/aa480157.aspx

        Type storageRootType = typeof(StorageInfo).Assembly.GetType("System.IO.Packaging.StorageRoot", true, false);
        object result = storageRootType.InvokeMember(methodName,
            BindingFlags.Static | BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.InvokeMethod,
            null, storageRoot, methodArgs);
        return result;
    }

    private static void WriteStorage(StorageInfo storageInfo, string storageName, XmlWriter writer)
    {
        writer.WriteStartElement("storage");
        writer.WriteAttributeString("name", storageName);

        StorageInfo[] subStorages = storageInfo.GetSubStorages();
        foreach (StorageInfo subStorage in subStorages)
        {
            WriteStorage(subStorage, subStorage.Name, writer);
        }

        StreamInfo[] streams = storageInfo.GetStreams();
        foreach (StreamInfo stream in streams)
        {
            string hexData = ConvertStreamBytesToHex(stream);
            writer.WriteStartElement("stream");
            writer.WriteAttributeString("name", stream.Name);
            writer.WriteAttributeString("data", hexData);
            writer.WriteEndElement();
        }

        writer.WriteEndElement();
    }

    private static string ConvertStreamBytesToHex(StreamInfo streamInfo)
    {
        using (Stream streamReader = streamInfo.GetStream(FileMode.Open, FileAccess.Read))
        {
            StringBuilder sb = new StringBuilder();
            int currentRead;
            while ((currentRead = streamReader.ReadByte()) >= 0)
            {
                byte currentByte = (byte)currentRead;
                sb.AppendFormat("{0:X2}", currentByte);
            }
            return sb.ToString();
        }
    }

    [DllImport("ole32.dll", CharSet = CharSet.Unicode)]
    private static extern int StgIsStorageFile(string fileName);

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