The Microsoft Caching Application Block contains a useful internal class that can be used to write/read meta-data to file on NTFS files, as I had to do recently.  Part of the app block is the MemoryMappedFileHelper.cs file which contains a ton of P/Invoke definitions including the Win32 function CreateFile, along with all it's related enums.  Here is one of the wrapper methods I created:

private static readonly string _fileDataStreamFormat="{0}:{1}";
public static byte[] GetAlternateDataStream(string fileName, string dataStreamName)
{
    if(dataStreamName.Trim().Length==0)
        throw new ArgumentException("dataStreamName must not be an empty string", "dataStreamName");
    string filePath = Path.GetFullPath(fileName);
    string adsPath = string.Format(_fileDataStreamFormat, filePath, dataStreamName);
    if(!File.Exists(filePath))
        throw new FileNotFoundException(string.Format("The file path '{0}' cannot be found.  
Please check the file location and provide full path info", filePath));
    IntPtr hFile = MemoryMappedFileHelper.CreateFile(adsPath
        , Win32FileAccess.GENERIC_READ
        , Win32FileShare.FILE_SHARE_READ
        , IntPtr.Zero
        , Win32FileMode.OPEN_ALWAYS
        , 0
        , IntPtr.Zero);
    FileStream stream = new FileStream(hFile, FileAccess.Read);
    int length = Convert.ToInt32(stream.Length);
    byte[] streamValues = new byte[length];
    try
    {
        int totalRead=0;
        while(totalRead<length)
        {
            totalRead+=stream.Read(streamValues, totalRead, length-totalRead);
        }
    }
    finally
    {
        stream.Close();
    }
    return streamValues;
}
This method takes in the file name and the name for the data stream and returns the byte[] data returned by the file system. You just have to de-serialize it into whatever form it takes: text, array or even .NET object graph. I have created several other methods to write to the stream and also to obtain a .NET FileStream to the alternate data stream (but I'll spare you the code dump here and upload them in zip format in the near future).