VB.NET XML parser loop

Question

Hey all i am new to XML parsing on VB.net. This is the code i am using to parse an XML file i have:

Dim output As StringBuilder = New StringBuilder()

Dim xmlString As String = _
    "<ip_list>" & _
        "<ip>" & _
            "<ip>192.168.1.1</ip>" & _
            "<ping>9 ms</ping>" & _
            "<hostname>N/A</hostname>" & _
         "</ip>" & _
         "<ip>" & _
             "<ip>192.168.1.6</ip>" & _
             "<ping>0 ms</ping>" & _
             "<hostname>N/A</hostname>" & _
         "</ip>" & _
   "</ip_list>"

Using reader As XmlReader = XmlReader.Create(New StringReader(xmlString))
        'reader.ReadStartElement("ip_list")

        Do Until reader.EOF
            reader.ReadStartElement("ip_list")
            reader.ReadStartElement("ip")
            reader.ReadStartElement("ip")
            reader.MoveToFirstAttribute()

            Dim theIP As String = reader.Value.ToString
            reader.ReadToFollowing("ping")
            Dim thePing As String = reader.ReadElementContentAsString().ToString
            reader.ReadToFollowing("hostname")
            Dim theHN As String = reader.ReadElementContentAsString().ToString

            MsgBox(theIP & " " & thePing & " " & theHN)
            reader.ReadEndElement()
        Loop

        reader.Close()
    End Using

I put the do until reader.EOF myself but it does not seem to work. It keeps giving an error after the first go around. I must be missing something?

David

SLaks · Accepted Answer · 2010-05-24 16:45:18Z

1

You never closed the first <ip> element.
Therefore, when the loop repeats, it tries to read a second <ip> inside the first one.

You need to call ReadEndElement() twice at the end of the loop.

answered May 24, 2010 at 16:45

SLaks

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5 Comments

StealthRT Over a year ago

Thanks for the comment. I added those twice at the end but it seems to not loop around again (only does it once)

StealthRT Over a year ago

Yeah, tried that as well and it still only shows one instead of 2. Gives the same error as before.

SLaks Over a year ago

Move reader.ReadStartElement("ip_list") outside the loop. (Since there is only one <ip_list> element)

StealthRT Over a year ago

Did that as well (notice i commented it out in the code above). Still the same issue though. It loops twice but on the 2nd it stops that the first "ip" with an error.

StealthRT Over a year ago

Sorry, there is no error BUT it does only loop once when using the ip_list outside the loop.

Gideon Engelberth · Accepted Answer · 2010-05-26 23:38:57Z

1

If you are able to use .NET 3.5, I would recommend using the XML literals and LINQ syntax.

Dim ips = From xe In XElement.Parse(xmlString).<ip> _
          Select New With {.IP = xe.<ip>.Value, _
                           .Ping = xe.<ping>.Value, _
                           .HostName = xe.<hostname>.Value}
'if you only want one
Dim firstIp = ips.First()

There's also an XElement.Load you can use to load from a file.

answered May 26, 2010 at 23:38

Gideon Engelberth

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