asked on

Select Single Node in VB.Net problems

Hi,

I'm having problems removing nodes from an XML file in vb.net 2003. I took my existing functioning VB6 code and altered this to reference the correct objects etc. However i just keep getting an error;

System.NullReferenceException: Object reference not set to an instance of an object. I am using the wrong object for oRefNode & oNode?

This is driving me mad an any ideas would be gratefully appreciated.
Thanks,
G

CODE BELOW
---------------------------------------------------------------------------------------------------

Dim mdocNewXmlDoc2 As XmlDocument
Dim oRefNode As XmlNode
Dim oNode As XmlNode

mdocNewXmlDoc2 = New XmlDocument
mdocNewXmlDoc2.Load("C:\Projects\CIS\xmlOut.xml")
oRefNode = mdocNewXmlDoc2.SelectSingleNode("/GovTalkMessage/Body/IRenvelope/IRheader")
oNode = mdocNewXmlDoc2.SelectSingleNode("/GovTalkMessage/Body/IRenvelope/IRheader/IRmark")
Try
If Not oNode.InnerText = vbNull Then
oRefNode.RemoveChild(oNode)
End If
Catch esc As SystemException
MsgBox("A system error ocurred" & vbNewLine & esc.ToString(), MsgBoxStyle.Critical)
Console.WriteLine("************************************************")
Console.WriteLine(esc.ToString())
End Try

Darren

The only thing that I do differently is

Dim oNodeRoot, oNode As XmlNode

' Load the root node with the entire document.
oNodeRoot = oXMLDOMDoc.DocumentElement

' Retrieve the required node using xPath.
oNode = oNodeRoot.SelectSingleNode("/Blah.Blah/BlehElement")

Darren

Darren

Never mind the . in the path. Once your path is correct.

1114godders

ASKER

Darren,

many thanks for that, however i am still getting an "System.NullReferenceException: Object reference not set to an instance of an object" on the RemoveChild function, i know i'm not far away from getiting this to work, but it feels like much further at the moment.

And the objectoNode is still null after;
oNode = oRefNode.SelectSingleNode("/GovTalkMessage/Body/IRenvelope/IRheader/IRmark")

mdocNewXmlDoc2 = New XmlDocument
mdocNewXmlDoc2.Load("C:\Projects\CIS\xmlOut.xml")
oRefNode = mdocNewXmlDoc2.DocumentElement
oNode = oRefNode.SelectSingleNode("/GovTalkMessage/Body/IRenvelope/IRheader/IRmark")
Try
oRefNode.RemoveChild(oNode)
Catch esc As SystemException
MsgBox("A system error ocurred" & vbNewLine & esc.ToString(), MsgBoxStyle.Critical)
Console.WriteLine(esc.ToString())
End Try

Darren

Can you put up you XML file??

1114godders

ASKER

Sure,
<?xml version="1.0" encoding="UTF-8"?>
<GovTalkMessage xmlns="http://www.govtalk.gov.uk/CM/envelope">
<EnvelopeVersion>2.0</EnvelopeVersion>
<Header>
<MessageDetails>
<Class>IR-CIS-VERIFY</Class>
<Qualifier>request</Qualifier>
<Function>submit</Function>
<CorrelationID/>
<Transformation>XML</Transformation>
<GatewayTest>1</GatewayTest>
<GatewayTimestamp/>
</MessageDetails>
<SenderDetails>
<IDAuthentication>
<SenderID>CIS161</SenderID>
<Authentication>
<Method>clear</Method>
<Role>principal</Role>
<Value>testing1</Value>
</Authentication>
</IDAuthentication>
</SenderDetails>
</Header>
<GovTalkDetails>
<Keys>
<Key Type="TaxOfficeNumber">123</Key>
<Key Type="TaxOfficeReference">R161</Key>
</Keys>
<ChannelRouting>
<Channel>
<URI>0772</URI>
<Product>HRWorks CIS</Product>
</Channel>
</ChannelRouting>
</GovTalkDetails>
<Body>
<IRenvelope xmlns="http://www.govtalk.gov.uk/taxation/CISrequest">
<IRheader>
<Keys>
<Key Type="TaxOfficeNumber">123</Key>
<Key Type="TaxOfficeReference">R161</Key>
</Keys>
<PeriodEnd>2008-04-05</PeriodEnd>
<Principal>
<Contact>
<Name>
<Ttl>Mr</Ttl>
<Fore>Brian</Fore>
<Sur>Cooper</Sur>
</Name>
<Email Preferred="yes">brian.cooper@wealden.net</Email>
<Telephone Mobile="no" Preferred="no" Type="work">
<Number>0208 3647177</Number>
</Telephone>
<Fax Mobile="no" Preferred="no" Type="work">
<Number>0208 3647181</Number>
</Fax>
</Contact>
</Principal>
<DefaultCurrency>GBP</DefaultCurrency>
<IRmark Type="generic"> </IRmark>
<Sender>Employer</Sender>
</IRheader>
<CISrequest>
<Contractor>
<UTR>9325648154</UTR>
<AOref>123PP87654321</AOref>
</Contractor>
<Subcontractor>
<Action>verify</Action>
<Type>company</Type>
<TradingName>Plastered</TradingName>
<WorksRef>ZA001</WorksRef>
<CRN>NE987654</CRN>
</Subcontractor>
<Declaration>yes</Declaration>
</CISrequest>
</IRenvelope>
</Body>
</GovTalkMessage>

Darren

Hi,

There is nothing wrong with what you are doing to pull out the nodes.

The problem is with the Namespaces. These seem to be causing a problem. If you take them out it works fine.

I'm don't know off the top of my head how to fix this but there is probably some setting or something.

Sorry I can't be of more help.

Darren

Code:

Dim mdocNewXmlDoc2 As New XmlDocument
Dim oRootNode As XmlNode
Dim oNode As XmlNode

Try
mdocNewXmlDoc2.Load("C:\Projects\CIS\xmlOut.xml")

oRootNode = mdocNewXmlDoc2.DocumentElement()

oNode = oRootNode.SelectSingleNode("/GovTalkMessage/Body/IRenvelope/IRheader/IRmark")

If Not oNode Is Nothing Then
oRootNode.RemoveChild(oNode)
End If
Catch esc As SystemException
MsgBox("A system error ocurred" & vbNewLine & esc.ToString(), MsgBoxStyle.Critical)
Console.WriteLine("************************************************")
Console.WriteLine(esc.ToString())
End Try

1114godders

ASKER

Darren,

Many thanks for that, by the Namespaces do you mean the ones in VB.Net? If i remove the namespaces won't the code just not run at all, im a bit confused here?

G

ASKER CERTIFIED SOLUTION

Darren

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1114godders

ASKER

Very strange, will need to think about this one a while, but i'll give you points for at least figuring out why it wasn't working.

Darren

I know it's really wierd

Have a look here

http://pluralsight.com/blogs/keith/archive/2005/10/19/15714.aspx

Darren

That article shows how to strip out the xmlns using regular expressions further down the post.

Probably better off reading the entire article comments and all.

Darren

Darren

Here's another article

http://www.devx.com/DevX/Tip/21337