How to parse and update xml file using xmltextreader or xmlreader

Question

Hi i have the following code to read the xml file and change the value of particular node ,but i want to do the same using xmltextreader or xmlreader, i am trying to avoid the statement doc.Save(System.Web.HttpContext.Current.Server.MapPath("Data/Example.xml")); , which has a direct reference to my physical file.

XmlDocument doc = new XmlDocument();
                   string xmlFile = System.Web.HttpContext.Current.Server.MapPath("Data/Example.xml");
                   doc.Load(xmlFile);
                   XmlNodeList xmlnode = doc.GetElementsByTagName("value");
                   xmlnode[0].ChildNodes[0].Value = 23;
 doc.Save(System.Web.HttpContext.Current.Server.MapPath("Data/Example.xml"));

Answer 1

Well something's going to have to have a reference to the file. However, you could easily change your code to simply accept a Stream (which would have to be readable, writable and seekable):

private static void ChangeDocument(Stream stream)
{
    XmlDocument doc = new XmlDocument();
    doc.Load(stream);
    XmlNodeList xmlnode = doc.GetElementsByTagName("value");
    xmlnode[0].ChildNodes[0].Value = 23;
    stream.Position = 0;
    doc.Save(stream);
    stream.SetLength(stream.Position); // Truncate the file if it was longer
}

It's somewhat ugly, admittedly...

Of course you could always pass in the filename itself - your MapPath call would still be in a higher level method, which may be all you're trying to achieve:

private static void ChangeDocument(string filename)
{
    XmlDocument doc = new XmlDocument();
    doc.Load(filename);
    XmlNodeList xmlnode = doc.GetElementsByTagName("value");
    xmlnode[0].ChildNodes[0].Value = 23;
    doc.Save(filename);
}

One final aside - if you're using .NET 3.5 or higher, I'd strongly recommend using LINQ to XML as a rather nicer XML API.