XML Error: There are multiple root elements

Question

I am getting XML from a web service. Here is what the XML looks like:

<parent>
    <child>
        Text
    </child>
</parent>
<parent>
    <child>
        <grandchild>
            Text
        </grandchild>
        <grandchild>
            Text
        </grandchild>
    </child>
    <child>
        Text
    </child>
</parent>

etc.

And here is my C# code:

StringBuilder output = new StringBuilder();

// Create an XmlReader
using (XmlReader reader = XmlReader.Create(new StringReader(xoResponse.@return)))
{
    XmlWriterSettings ws = new XmlWriterSettings();
    //ws.Indent = true;
    using (XmlWriter writer = XmlWriter.Create(output, ws))
    {
        // Parse the file and display each of the nodes.
        while (reader.Read())
        {
            switch (reader.NodeType)
            {
                case XmlNodeType.Element:
                    writer.WriteStartElement(reader.Name);
                    break;
                case XmlNodeType.Text:
                    writer.WriteString(reader.Value);
                    break;
                case XmlNodeType.XmlDeclaration:
                case XmlNodeType.ProcessingInstruction:
                    writer.WriteProcessingInstruction(reader.Name, reader.Value);
                    break;
                case XmlNodeType.Comment:
                    writer.WriteComment(reader.Value);
                    break;
                case XmlNodeType.EndElement:
                    writer.WriteFullEndElement();
                    break;
            }
        }
    }
}

I believe that the error is thrown on the second parent element. How can I avoid this error? Any help is greatly appreciated.

Answer 1

You can do it without modifying the XML stream: Tell the XmlReader to not be so picky. Setting the XmlReaderSettings.ConformanceLevel to ConformanceLevel.Fragment will let the parser ignore the fact that there is no root node.

        XmlReaderSettings settings = new XmlReaderSettings();         settings.ConformanceLevel = ConformanceLevel.Fragment;         using (XmlReader reader = XmlReader.Create(tr,settings))         {              ...         } 

Now you can parse something like this (which is an real time XML stream, where it is impossible to wrap with a node).

<event>   <timeStamp>1354902435238</timeStamp>   <eventId>7073822</eventId> </event> <data>   <time>1354902435341</time>   <payload type='80'>7d1300786a0000000bf9458b0518000000000000000000000000000000000c0c030306001b</payload> </data> <data>   <time>1354902435345</time>   <payload type='80'>fd1260780912ff3028fea5ffc0387d640fa550f40fbdf7afffe001fff8200fff00f0bf0e000042201421100224ff40312300111400004f000000e0c0fbd1e0000f10e0fccc2ff0000f0fe00f00f0eed00f11e10d010021420401</payload> </data> <data>   <time>1354902435347</time>   <payload type='80'>fd126078ad11fc4015fefdf5b042ff1010223500000000000000003007ff00f20e0f01000e0000dc0f01000f000000000000004f000000f104ff001000210f000013010000c6da000000680ffa807800200000000d00c0f0</payload> </data> 

Answer 2

You need to enclose your <parent> elements in a surrounding element as XML Documents can have only one root node:

<parents> <!-- I've added this tag -->     <parent>         <child>             Text         </child>     </parent>     <parent>         <child>             <grandchild>                 Text             </grandchild>             <grandchild>                 Text             </grandchild>         </child>         <child>             Text         </child>     </parent> </parents> <!-- I've added this tag --> 

As you're receiving this markup from somewhere else, rather than generating it yourself, you may have to do this yourself by treating the response as a string and wrapping it with appropriate tags, prior to attempting to parse it as XML.

So, you've a couple of choices:

1. Get the provider of the web service to return you actual XML that has one root node
2. Pre-process the XML, as I've suggested above, to add a root node
3. Pre-process the XML to split it into multiple chunks (i.e. one for each <parent> node) and process each as a distinct XML Document

Answer 3

Wrap the xml in another element

<wrapper>
<parent>
    <child>
        Text
    </child>
</parent>
<parent>
    <child>
        <grandchild>
            Text
        </grandchild>
        <grandchild>
            Text
        </grandchild>
    </child>
    <child>
        Text
    </child>
</parent>
</wrapper>