Question

I am using JQuery to perform async calls to a WebService written in C#. The WebService invokes a Stored Procedure (located in a SQL Server Database). The stored procedure returns results as XML (I use ‘for xml’ in the procedure to retrieve the result as XML).

The question is: How can I place the XML returned by the stored procedure (that is streamed by SQL Server) on to the HTTP Response stream of the WebService with the least amount of memory and processing time usage.

At the moment, my WebService returns XmlDocument object.I would like to know if there is a way to reduce the overhead of creation of XmlDocument or DataSet Objects, which consume both memory and processor time.

Ideal solution would be:
Connect the result stream pipe from SQL Server to the HTTP Response stream pipe. This way, whatever is coming from SQL Server will get to the client without the content being touched. No new objects are created (like DataSet, XmlDocument) and XmlParsing is avoided while creating XmlDocuments. Thus keeping the memory and processing footprint to the least. Also, whether the XML returned by the procedure is small or very large, since streams are used, memory usage will not grow (which is the case is XmlDocuments are created).

My reduced c# webservice method:

public XmlDocument GetXmlDataFromDB()
{
    string connStr = System.Convert.ToString(
            System.Web.Compilation.ConnectionStringsExpressionBuilder.GetConnectionString("DbConnectionString"),
            System.Globalization.CultureInfo.CurrentCulture);

    SqlConnection conn = new SqlConnection(connStr);
    SqlCommand sqlCmd = new SqlCommand("stp_GetXmlData", conn);
    sqlCmd.CommandType = CommandType.StoredProcedure;

    SqlDataAdapter sda = new SqlDataAdapter(sqlCmd);
    DataSet ds = new DataSet();
    conn.Open();

    XmlReader xmlReader = sqlCmd.ExecuteXmlReader();

    while (xmlReader.Read())
    {
        ds.ReadXml(xmlReader);
    }

    conn.Close();

    XmlDocument xmlDoc = new XmlDocument();
    xmlDoc.InnerXml = ds.GetXml();

    return xmlDoc;
}

Any suggestions to improve the performance of the above code?

Answer 1

In your code, you don’t need DataSet, SqlDataAdapter and InnerXml

var doc = new XmlDocument();
...

var reader = cmd.ExecuteXmlReader();
if (reader.Read())
 doc.Load(reader);

Alternatively you can use reader.ReadOuterXml() to get xml as string,without constructing a document.

Also you can think of using WCF Services for ASP.NET AJAX