How to create a XmlDocument using XmlWriter in .NET?

Question

Many .NET functions use XmlWriter to output/generate xml. Outputting to a file/string/memory is a very operation:

XmlWriter xw = XmlWriter.Create(PutYourStreamFileWriterEtcHere);
xw.WriteStartElement("root");
...

Sometimes , you need to manipulate the resulting Xml and would therefore like to load it into a XmlDocument or might need an XmlDocument for some other reason but you must generate the XML using an XmlWriter. For example, if you call a function in a 3rd party library that outputs to a XmlWriter only.

One of the things you can do is write the xml to a string and then load it into your XmlDocument:

StringWriter S = new StringWriter();
XmlWriter xw = XmlWriter.Create(S);
/* write away */
XmlDocument xdoc = new XmlDocument();
xdoc.LoadXml(S.ToString());

However this is inefficient - first you serialize all the xml info into a string, then you parse the string again to create the DOM.

How can you point an XmlWriter to build a XmlDocument directly?

Answer 1

Here's at least one solution:

XmlDocument doc = new XmlDocument(); 
using (XmlWriter writer = doc.CreateNavigator().AppendChild()) 
{ 
    // Do this directly 
     writer.WriteStartDocument(); 
     writer.WriteStartElement("root"); 
     writer.WriteElementString("foo", "bar"); 
     writer.WriteEndElement(); 
     writer.WriteEndDocument();
    // or anything else you want to with writer, like calling functions etc.
}

Apparently XpathNavigator gives you a XmlWriter when you call AppendChild()

Credits go to Martin Honnen on : http://groups.google.com/group/microsoft.public.dotnet.xml/browse_thread/thread/24e4c8d249ad8299?pli=1

Answer 2

You could do the opposite : build the XmlDocument first using DOM, then write it to a XmlWriter :

XmlDocument xdoc = new XmlDocument();
... // build the document

StringWriter S = new StringWriter();
XmlWriter xw = XmlWriter.Create(S);
xdoc.WriteTo(xw);

Answer 3

You can write xml file using XMLWriter class. Here is example for this.

    XmlWriterSettings objSetting = new XmlWriterSettings();
    objSetting.Indent = true;
    objSetting.NewLineOnAttributes = true;

    System.Text.StringBuilder sb = new System.Text.StringBuilder();


    using (XmlWriter objWriter = XmlWriter.Create(sb, objSetting))
    {
        //Note the artificial, but useful, indenting
        objWriter.WriteStartDocument();

        objWriter.WriteStartElement("books");

        ////////Start Book Element///////

        objWriter.WriteStartElement("book");

        objWriter.WriteStartAttribute("ISBN");
        objWriter.WriteValue("asp1");
        objWriter.WriteEndAttribute();

        objWriter.WriteStartElement("Title");
        objWriter.WriteValue("ASP.NET");
        objWriter.WriteEndElement();

        objWriter.WriteElementString("ReleaseDate", "11/11/2010");

        objWriter.WriteStartElement("Pages");
        objWriter.WriteValue(200);
        objWriter.WriteEndElement(); //price

        objWriter.WriteEndElement(); //book
        ////////End Book Element///////


        ////////Another Element

        ////////Start Book Element///////

        objWriter.WriteStartElement("book");

        objWriter.WriteStartAttribute("ISBN");
        objWriter.WriteValue("c#2");
        objWriter.WriteEndAttribute();

        objWriter.WriteStartElement("Title");
        objWriter.WriteValue("C#.NET");
        objWriter.WriteEndElement();

        objWriter.WriteElementString("ReleaseDate", "10/11/2010");

        objWriter.WriteStartElement("Pages");
        objWriter.WriteValue(500);
        objWriter.WriteEndElement(); 

        objWriter.WriteEndElement(); //book
        ////////End Book Element///////



        objWriter.WriteEndElement(); //books
        objWriter.WriteEndDocument();

    }

    File.WriteAllText(Server.MapPath("BooksList.xml"), sb.ToString());

Answer 4

The idea behind XmlWriter is to wait until you have finished modifying your data before you start writing.

XmlWriter wasn't built with your situation in mind.

Either

• Wait until you know what your data is going to be before writing

or

• Do what you're currently doing

Answer 5

There is an underlying Stream object that the XmlWriter was writing to, if it was bidirectional (MemoryStream), you could simply re-position it back to -0- and then use the Stream object in the XmlDocument.Load(stream).

HTH,

Z