check an xml node is not nothing

Question

i am using in vb.net to load an Xml
Dim SrvrSetXml As New XmlDocument()
SrvrSetXml.Load("C:\Users\" & UserNameP() & "\AppData\Roaming\ProgVndr\ProgsOpn.xml")
Dim erPWndXmlFile As XmlNodeList = SrvrSetXml.DocumentElement.SelectNodes("/dataroot/ProgsOpn")
For Each node As XmlNode In erPWndXmlFile
My.MySettings.Default.UnitID2 = (node.SelectSingleNode("UnitID2").InnerText)
Next
if the node is empty it is making an error
System.NullReferenceException: 'Object reference not set to an instance of an object.'
System.Xml.XmlNode.SelectSingleNode(...) returned Nothing.

to prevent this error i am trying
if not (node.SelectSingleNode("UnitID2").InnerText) is nothing then
it dosnt help the same error massage appers

Answer 1

Hi @Simon ,

Please try the following solution.

VB.NET

Sub Main  
	Const filename As String = "e:\Temp\ProgsOpn.xml"  
	Dim xdoc As XDocument = XDocument.Load(filename)  

	Dim ProgsOpn = xdoc.Descendants("ProgsOpn")  
  
	For Each elem In ProgsOpn.Elements()  
		Console.WriteLine($"{elem.Name}='{elem.Value}'")  
	Next  
  
	Dim el1 As String = xdoc.Descendants("UnitIDO").FirstOrDefault()?.Value  
	Dim el2 As String = xdoc.Descendants("NotExistingElement").FirstOrDefault()?.Value  
	  
	Console.WriteLine($"existing element: {el1}")  
	Console.WriteLine($"not existing element: {el2}")  
End Sub  

Answer 2

this is the xml sample

<dataroot xmlns:od="urn:schemas-microsoft-com:officedata" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="ProgsOpn.xsd" generated="2022-02-17T10:56:41">
<ProgsOpn>
<ID>1</ID>
<Unapld>26</Unapld>
<QuitMain>True</QuitMain>
<Tnnts>26</Tnnts>
<TnntID>111132</TnntID>
<TnntID2>100016</TnntID2>
<TnntIDO>111140</TnntIDO>
<Prprty>0</Prprty>
<PrptID>24</PrptID>
<PrptID2>100002</PrptID2>
<PrptIDO>5</PrptIDO>
<Units>0</Units>
<UnitID>83</UnitID>
<UnitIDO>101922</UnitIDO>
<Stf>26</Stf>
<StfID>100171</StfID>
<StfID2>100171</StfID2>
<StfIDO>100338</StfIDO>
<Vndrs>26</Vndrs>
<VndrID>388</VndrID>
<VndrID2>808</VndrID2>
<VndrIDO>918</VndrIDO>
<Workrs>26</Workrs>
<WorkID>11</WorkID>
<WorkIDO>437</WorkIDO>
<OnrIDO>987</OnrIDO>
<Owners>26</Owners>
<OwnID>21</OwnID>
<OwnID2>957</OwnID2>
<OwnIDO>437</OwnIDO>
</ProgsOpn>
</dataroot>