Compressing directly from a stream

Question

I have a simple application that retrieves a dataset from the database and converts it to an xml file. This xml file is then read in and compressed to a .gz file.

This seems pretty inefficient - is it possible to skip the step of writing to a temporary .xml file and reading it back into compress it? Can I automatically send the file to a stream which converts it directly to a converted xml format?

Here is my code:

public partial class _Default : System.Web.UI.Page
{
    DataSet dataset = new DataSet();
    string uri = "C:\\tester.xml";
    string compressedfileuri = "C:\\tester.gz";

    protected void Page_Load(object sender, EventArgs e)
    {            
        //get the dataset
        RetrieveData();

        //serialize data to a xml file
        dataset.WriteXml(uri);

        //compress the data
        Compress();
    }

    public void RetrieveData()
    {
        string connString = ConfigurationManager.ConnectionStrings["Platform"].ConnectionString;
        using (SqlConnection conn = new SqlConnection(connString))
        {
            SqlDataAdapter adapter = new SqlDataAdapter();
            adapter.SelectCommand = new SqlCommand("SELECT * FROM expenses.CST_COSTHEADER", conn);
            adapter.Fill(dataset);                
        }
    }

    public void Compress()
    {
        using (FileStream fs = new FileStream(uri, FileMode.Open))
        {
            using (FileStream outFile = File.Create(compressedfileuri))
            {
                using (GZipStream Compress = new GZipStream(outFile, CompressionMode.Compress))
                {
                    fs.CopyTo(Compress);
                }
            }
        }
    }
}

Answer 1

In another answer you mention you have not seen any examples of how to write directly from WriteXML to a stream. Here is how to stream directly to the file using your code as a base.

public void RetrieveData(Stream outputStream)
{
    string connString = ConfigurationManager.ConnectionStrings["Platform"].ConnectionString;
    using (SqlConnection conn = new SqlConnection(connString))
    using (GZipStream compressStream = new GZipStream(outputStream, CompressionMode.Compress))
    {
        SqlDataAdapter adapter = new SqlDataAdapter();
        adapter.SelectCommand = new SqlCommand("SELECT * FROM expenses.CST_COSTHEADER", conn);
        adapter.Fill(dataset);   
        dataSet.WriteXml(compressStream);             
    }
}

---

For fun here is a version that is done as a extension method, you can just use it as dataset.WriteCompressedXml(stream)

public static class ExtensionMethods
{
    public static void WriteCompressedXml(this DataSet dataset, Stream stream)
    {
        using (GZipStream compressStream = new GZipStream(stream, CompressionMode.Compress))
        {  
            dataSet.WriteXml(compressStream);             
        }
    }

    public static void WriteCompressedXml(this DataSet dataset, Stream stream, XmlWriteMode mode)
    {
        using (GZipStream compressStream = new GZipStream(stream, CompressionMode.Compress))
        {  
            dataSet.WriteXml(compressStream, mode);             
        }
    }
}