reading xml using xml parser

Question

I need to get user id corresponding terminal id. any help. But it's giving error:

The ReadElementContentAsString method is not supported on node type None. Line 1, position 668.

 string strTerminalId = "E";
 XmlDocument xdoc = new XmlDocument();
 xdoc.LoadXml(STRING); //
 string strxml = xdoc.OuterXml;
 string strUserName = "";
 bool Flag = false;

 using (XmlReader reader = XmlReader.Create(new StringReader(strxml)))
 {
     while (reader.Read())
     {
         if (reader.IsStartElement())
         {
             switch (reader.Name)
             {
                 case "Row":
                     reader.Read();
                     if (Flag == false)
                     {
                         reader.ReadToFollowing("TERM-ID");
                         reader.Read();
                         string strTERMID = reader.ReadElementContentAsString().ToString();
                          if (strTERMID == strTerminalId)
                                {
                                    while (reader.ReadToFollowing("NA") && (Flag == false))
                                    {
                                        reader.Read();
                                        string strUser = reader.ReadContentAsString();
                                        if (strUser == "NA")
                                        {
                                            reader.ReadToFollowing("c:value");
                                            reader.Read();
                                            strUserName = reader.ReadContentAsString();
                                            Flag = true;
                                        }
                                    }
                                }
                            }
                            break;
                    }
                }
            }

The content of the XML document is

<GetReferenceTableResponse xmlns='http://tempuri.org/'>
    <GetReferenceTableResult> 
        <Table Name='C' ID='46899' xmlns=''>   
            <Columns>
            <Col ID='7442' Name='TD' Datatype='T' Length='8' AttributeDescription='Terminal ID' IsKey='Y'/>
            <Col ID='7443' Name='D' Datatype='T' Length='50' AttributeDescription='Description' IsKey=' '/>
            <Col ID='7444' Name='U' Datatype='T' Length='8' AttributeDescription='USER-ID' IsKey='' />
            </Columns> 
            <Rows>
                <Row RowsetID=\"1\">
                    <TERM-ID ID='279598'>A</TERM-ID>
                    <DESC-TXT ID='279622'>ASC</DESC-TXT>  
                    <USER-ID ID='279646'>A</USER-ID>
                </Row>
            </Rows> 
        </Table> 
    </GetReferenceTableResult>
</GetReferenceTableResponse>

what is the error? please edit your question, providing more details, and better give all the code inside the using statement (using (XmlReader reader) — kennyzx
– kennyzx, Commented Nov 25, 2014 at 4:17
parsing xml document using XmlReader is very inefficient. do you consider using XDocument or XPath? just a few lines of code; or do you have to stick to XmlReader? — kennyzx
– kennyzx, Commented Nov 25, 2014 at 4:28
@kennyzx - "inefficient" is an interesting term for fastest way of parsing XML using classes that are part of network. Harder to get right than XDocument/XmlDocument - indeed... — Alexei Levenkov
– Alexei Levenkov, Commented Nov 25, 2014 at 4:32
@AlexeiLevenkov well, can help me with the choice of word, maybe verbose?? when i typed efficient i meant "using less code", not "highest performance". — kennyzx
– kennyzx, Commented Nov 25, 2014 at 4:37
What are your performance considerations? @Alexei is correct that XMLReader is better choice for performance. But if that is not the case you can use LINQ. Much easier and readable constructs. — Piyush Parashar
– Piyush Parashar, Commented Nov 25, 2014 at 4:43

JleruOHeP · Accepted Answer · 2014-11-25 05:00:26Z

ReadToFollowing navigates to the nearest element with a given name and the next Read will go inside that element - straight to the Text. So you would need ReadContentAsString in both cases.

In your case that would work:

using (XmlReader reader = XmlReader.Create(new StringReader(strxml)))
{
    while (reader.Read())
    {
        if (reader.IsStartElement())
        {
            switch (reader.Name)
            {
                case "Row":                     
                    if (!Flag)
                    {
                        reader.ReadToFollowing("TERM-ID");
                        reader.Read();
                        string strTERMID = reader.ReadContentAsString();                         
                        if (strTERMID == strTerminalId && reader.ReadToNextSibling("USER-ID"))
                        {
                            reader.Read();
                            strUserName = reader.ReadContentAsString();
                            Flag = true;
                        }
                    }
                    break;
            }
        }
    }
}

I have removed the first Read just after case "Row": - otherwise you would miss the proper element and as well removed ReadToFollowing("USER-ID") from the while loop - it is okey to go into the element only once.

But as @kennyzx said - it is much simpler to parse the xml using XDoccument.

UPDATE I am not sure about your schema but if it is possible for a Row element to not have User-Id, then with ReadToFollowing it is possible to skip to the next available 'User-ID' element, even if it is not in the same 'Row' element. So it is better to use ReadToNextSibling in the second case.

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