Solved

Ignore missing nodes in XMLDocument

Posted on 2010-11-30
7
376 Views
Last Modified: 2012-05-10
Hi Experts,

If I'm reading in using XMLReader like so:

            userSurName = m_node.SelectSingleNode("BillingData/BuyerName").InnerText
            userEmail = m_node.SelectSingleNode("BillingData/BuyerEmailAddress").InnerText
            userAddress1 = m_node.SelectSingleNode("FulfillmentData/Address/AddressFieldOne").InnerText
            userAddress2 = m_node.SelectSingleNode("FulfillmentData/Address/AddressFieldTwo").InnerText

...and sometimes one of these nodes doesn't exist, it will error with: "System.NullReferenceException: Object reference not set to an instance of an object."

what's the best way to deal with this, please?  

Thanks
0
Comment
Question by:jammy-d0dger
  • 4
  • 2
7 Comments
 
LVL 32

Assisted Solution

by:Erick37
Erick37 earned 200 total points
ID: 34239041
Test the node first before calling InnerText()

node = m_node.SelectSingleNode("BillingData/BuyerName")
If node IsNot Nothing Then
    userSurName = node.InnerText
End If
0
 
LVL 12

Assisted Solution

by:HugoHiasl
HugoHiasl earned 300 total points
ID: 34239082
The problem is that the term

m_node.SelectSingleNode("FulfillmentData/Address/AddressFieldOne")

is not returning an object but you try directly to access the InnerText-Property of the object that was not returned.

You can check this for every row like:

userSurName = m_node.SelectSingleNode("BillingData/BuyerName") == null ? "" : m_node.SelectSingleNode("BillingData/BuyerName").InnerText:


Or you create a small function handling this more convenient:

userSurName = getMyNode(m_node, "BillingData/BuyerName");

private string getMyNode(XmlNode myNode, string xPathString) {
  return myNode.SelectSingleNode(xPathString) == null ? "" : myNode.SelectSingleNode(xPathString).InnerText:
}

0
 

Author Comment

by:jammy-d0dger
ID: 34239141
HugoHiasl: is there any way you can convert that to vb for me?  
0
Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 

Author Comment

by:jammy-d0dger
ID: 34239359
OK, think I'm nearly there.  My conversion of what you suggested is:

    Public Shared Function getXMLNodeValue(ByVal currentNode As XmlNode, ByVal xPathString As String) As String
        If currentNode Is Nothing Then
            getXMLNodeValue = ""
        Else
            getXMLNodeValue = currentNode.SelectSingleNode(xPathString).InnerText
        End If
    End Function

called by:            
 userAddress2 = getXMLNodeValue(m_node, "FulfillmentData/Address/AddressFieldTwo")

However, when I run this, it all works except when AdressFieldTwo isn't present and then it still tries to do "getXMLNodeValue = currentNode.SelectSingleNode(xPathString).InnerText" which leads me to believe that "'Is Nothing" is not the correct test?


0
 

Accepted Solution

by:
jammy-d0dger earned 0 total points
ID: 34239453
Sorted it.  For completeness in case anyone else searches for this:

    Public Shared Function getXMLNodeValue(ByVal currentNode As XmlNode, ByVal xPathString As String) As String
        If currentNode.SelectSingleNode(xPathString) Is Nothing Then
            getXMLNodeValue = ""
        Else
            getXMLNodeValue = currentNode.SelectSingleNode(xPathString).InnerText
        End If
    End Function

I was comparing against the wrong node/path.  All good now.
0
 
LVL 32

Expert Comment

by:Erick37
ID: 34239485
Use the method I gave you.
You should not call InnerText on the SelectSingleNode until you know that it is not Nothing.

Example:
Dim node As XMLNode = m_node.SelectSingleNode("BillingData/BuyerName")
If node IsNot Nothing Then
    userSurName = node.InnerText
Else
    userSurName = String.Empty
End If
0
 

Author Closing Comment

by:jammy-d0dger
ID: 34276707
Guys, thanks for the steer in the right direction. Few more points to Hugo, for suggesting the function approach which is much cleaner.
0

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Today is the age of broadband.  More and more people are going this route determined to experience the web and it’s multitude of services as quickly and painlessly as possible. Coupled with the move to broadband, people are experiencing the web via …
In .NET 2.0, Microsoft introduced the Web Site.  This was the default way to create a web Project in Visual Studio 2005.  In Visual Studio 2008, the Web Application has been restored as the default web Project in Visual Studio/.NET 3.x The Web Si…
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …

828 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question