how to add nodes to an existing xml file using vb.net

ammu86 · January 5th, 2010, 03:41 AM

hi friends,
I have an xml file and i add a node to it using the following code.

LoadXmlDoc.Load("first.XML")
LoadXmlDoc_2.Load("second.XML")
Dim NodeToCreateOrReplace_2 As XmlNodeList = LoadXmlDoc_2.GetElementsByTagName("SB")
Dim NodeToCreateOrReplace As XmlNodeList = LoadXmlDoc.GetElementsByTagName("SB")
Dim newnode As XmlNode, currNode
'XmlNodeList NodeToCreateOrReplace = LoadXmlDoc.GetElementsByTagName(XmlTagNameTxtBx.Te xt);
Try
For Each selectednode As XmlNode In NodeToCreateOrReplace
Dim node As XmlNode = selectednode.SelectSingleNode("SBN")
For Each selectednode1 As XmlNode In LoadXmlDoc_2
Dim node_2 As XmlNode = selectednode.SelectSingleNode("SBN")
If node.InnerText = node_2.InnerText Then
' newnode = LoadXmlDoc.CreateElement("SB")
Dim docFrag As XmlDocumentFragment = doc.CreateDocumentFragment()
docFrag.InnerXml = selectednode1.OuterXml
currNode = LoadXmlDoc.DocumentElement("SBS").SelectSingleNode ("SB")
currNode.InsertAfter(LoadXmlDoc.ImportNode(docFrag , True), currNode.lastChild)

End If
Next
Next

im getting error "The element list has changed. The enumeration operation failed to continue."
please help.

samjudson · January 5th, 2010, 04:58 AM

I tried to put your code into a VB project but I couldn't work out what you are trying to do. The doc variable isn't declared, so I'm not sure what that is meant to be and you have missed the end of the code as the Try is without a Catch or Finally.

Generally you get the error you mention if you add or delete an item from whatever you are iterating over - in this case one of the two For Each loops.

Perhaps if you tell us a bit about the XML and what you are actually trying to do we could help.

ammu86 · January 5th, 2010, 05:50 AM

sorry,
My code have some errors..
this is the updated one.
@samjudson
this is vb.net code not vb.

Here i have two xml files.
im comparing second.xml with first.xml and if there is any similar nodes in these files , the node in second.xml will replace the nodes in first.xml

LoadXmlDoc.Load("first.XML")
LoadXmlDoc_2.Load("second.XML")
Dim NodeToCreateOrReplace_2 As XmlNodeList = LoadXmlDoc_2.GetElementsByTagName("SB")
Dim NodeToCreateOrReplace As XmlNodeList = LoadXmlDoc.GetElementsByTagName("SB")
Dim newnode As XmlNode, currNode
Try
For Each selectednode As XmlNode In NodeToCreateOrReplace
Dim node As XmlNode = selectednode.SelectSingleNode("SBN")
For Each selectednode1 As XmlNode In LoadXmlDoc_2
Dim node_2 As XmlNode = selectednode.SelectSingleNode("SBN")
If node.InnerText = node_2.InnerText Then
Dim docFrag As XmlDocumentFragment = LoadXmlDoc.CreateDocumentFragment()
docFrag.InnerXml = selectednode1.OuterXml
currNode = LoadXmlDoc.DocumentElement("SBS").SelectSingleNode ("SB")
currNode.InsertAfter(LoadXmlDoc.ImportNode(docFrag , True), currNode.lastChild)

End If
Next
Next
Catch ex As Exception
End Try

samjudson · January 5th, 2010, 06:46 AM

Yes, I meant VB.Net.

That compiles, but without the XML I still don't know what you are trying to accomplish.

Dim node_2 As XmlNode = selectednode.SelectSingleNode("SBN")

This line refers to selectedNode - perhaps you mean selectedNode1?

Also NodeToCreateOrReplace_2 is never used, currNode is declared as an Object, not an XmlNode, and newnode is never used.

You could make you code much easier to read with better naming conventions. Also, there is no need to create the document fragment at all really. And you could select the list of nodes easier if you used xpath I suspect.

ammu86 · January 6th, 2010, 12:25 AM

hi.........

Quote:

Originally Posted by samjudson

Yes, I meant VB.Net.

That compiles, but without the XML I still don't know what you are trying to accomplish.

Samjudson,
here i loaded two xml files..LoadXmlDoc & LoadXmlDoc_2 and if any similar nodes are there that particular node of loadxmldoc_2 will insert just after the existing node of loadxmldoc according to the criteria.

Dim node_2 As XmlNode = selectednode.SelectSingleNode("SBN")

This line refers to selectedNode - perhaps you mean selectedNode1?

this is wrong..i mean selectednode1. sorry for the mistake.

Also NodeToCreateOrReplace_2 is never used, currNode is declared as an Object, not an XmlNode, and newnode is never used.

I changed the currNode as XMLNode.Still the same issue.
yes..this is only a test code..i will try to make names much easier.

without document fragment i think its not possible to insert a node to a particular position.ie i want to specify where to insert the node exactly.

You could make you code much easier to read with better naming conventions. Also, there is no need to create the document fragment at all really. And you could select the list of nodes easier if you used xpath I suspect.

samjudson · January 6th, 2010, 04:25 AM

XmlDocument.ImportNode works just fine using the original node, rather than the document fragment:

Code:

currNode.InsertAfter(LoadXmlDoc.ImportNode(selectednode1 , True), currNode.lastChild)

Perhaps you could give a small example of the two XML documents and what you expect the output to look like?

ammu86 · January 6th, 2010, 04:47 AM

hi................

Quote:

Originally Posted by samjudson

XmlDocument.ImportNode works just fine using the original node, rather than the document fragment:

Import node will work only if the node wants to be add at the end of the document and it's not possible to specify the location where it to be inserted.

Code:

currNode.InsertAfter(LoadXmlDoc.ImportNode(selectednode1 , True), currNode.lastChild)

Perhaps you could give a small example of the two XML documents and what you expect the output to look like?

here im giving a simple example of two files.
first.xml
<root>
<person>
<name>a</name>
<age>25</age>
</person>

<person>
<name>b</name>
<age>35</age>
<person>
</root>

second.xml
<root>
<person>
<name>a</name>
<age>28</age>
</person>

so i want the output as follows

<root>
<person>
<name>a</name>
<age>25</age>
</person>
<root>
<person>
<name>a</name>
<age>28</age>
</person>
<person>
<name>b</name>
<age>35</age>
<person>
</root>

not like this
<root>
<person>
<name>a</name>
<age>25</age>
</person>

<person>
<name>b</name>
<age>35</age>
<person>

<person>
<name>a</name>
<age>28</age>
</person>
</root>

samjudson · January 6th, 2010, 05:13 AM

ImportNode doesn't insert the node you are importing into the tree, that is the job of InsertAfter, which I am still using exactly as in your original code, therefore my code should work just fine thanks.

Your example XML above makes no reference to the SB, SBN etc elements, therefore I can't use it to work out what your code is trying to do.

ammu86 · January 6th, 2010, 06:08 AM

hi........................

Quote:

Originally Posted by samjudson

ImportNode doesn't insert the node you are importing into the tree, that is the job of InsertAfter, which I am still using exactly as in your original code, therefore my code should work just fine thanks.

I gave only a sample of how to be the output should be.
Here is the original xml files that im using.

first.xml
<root>
<SB>
<SBN>1010</SBN>
<SBCN>0</SBCN>
<SBMID>11</SBMID>
</SB>
<SB>
<SBN>1020</SBN>
<SBCN>0</SBCN>
<SBMID>11</SBMID>
</SB>
</root>

second.xml
<root>
<SB>
<SBN>1010</SBN>
<SBCN>25</SBCN>
<SBMID>11</SBMID>
</SB>

<SB>
<SBN>1010</SBN>
<SBCN>50</SBCN>
<SBMID>11</SBMID>
</SB>
</root>

output should be
<root>
<SB>
<SBN>1010</SBN>
<SBCN>0</SBCN>
<SBMID>11</SBMID>
</SB>

<SB>
<SBN>1010</SBN>
<SBCN>0</SBCN>
<SBMID>11</SBMID>
</SB>
<SB>
<SBN>1010</SBN>
<SBCN>25</SBCN>
<SBMID>11</SBMID>
</SB>

<SB>
<SBN>1010</SBN>
<SBCN>50</SBCN>
<SBMID>11</SBMID>
</SB>
<SB>
<SBN>1020</SBN>
<SBCN>0</SBCN>
<SBMID>11</SBMID>
</SB>
</root>

Your example XML above makes no reference to the SB, SBN etc elements, therefore I can't use it to work out what your code is trying to do.

samjudson · January 6th, 2010, 07:22 AM

Try something like this:

Code:

        doc1.Load("first.XML")
        doc2.Load("second.XML")
        Dim nodeList1 As XmlNodeList = doc1.SelectNodes("//SB/SBN")
        Dim nodeList2 As XmlNodeList = doc2.SelectNodes("//SB/SBN")

        Try
            For Each selectednode1 As XmlNode In nodeList1

                For Each selectednode2 As XmlNode In nodeList2
                    If selectednode1.InnerText = selectednode2.InnerText Then
                        Dim newNode As XmlNode = doc1.ImportNode(selectednode2.ParentNode, True)
                        doc1.SelectSingleNode("root").InsertAfter(newNode, selectednode1.ParentNode)
                    End If
                Next
            Next
        Catch ex As Exception
        End Try

It might not be exactly what you are after, but should give you some hints on how to go about doing things better.