Linq to XML check for null results

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The following code works if data exist in the xml file. However, their times when datafield.tag.value(“90”) doesn’t exist. How can I check for null results.
example

if Num090 = Null then
Num090 = empty string

Appreciate your help.

Dim xd As XElement = XElement.Load(strFilename)
Dim strPipe As String = Chr(124)
Dim strSpace As String = Chr(10)
Dim strFinalString As String = ""
Dim Records = (From datafields In xd.Descendants("record") Select datafields)
For Each ser As XElement In Records
     Try
           Dim Num090 = (From datafield In ser.Descendants("datafield") Where (datafield.Attribute("tag").Value = "090")
           Select datafield.Elements.ElementAt(0))

           Dim DTIC856 = (From datafield In ser.Descendants("datafield") Where (datafield.Attribute("tag").Value = "856")
           Select datafield).Skip(1).First()
              

     Catch ex As Exception

     Finally

     End Try

Next

Posted 6-May-11 6:03am

stopete82

Updated 6-May-11 6:06am

Umair Feroze

v2

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2 solutions

Solution 2

Why do you want to reassign a var that was previously assigned as a XElement to a string if it's null?

If there's anything you want to do to Num090 after setting it to a value, I'd move the declaration outside the Try block, and do your post processing in the Finally block.

Posted 6-May-11 6:20am

#realJSOP

Comments

stopete82 6-May-11 13:01pm

For the fallowing code I want to capture the value for Num090 but sometimes it won't have a value.

with value xml file:
<datafield tag="090" ind1="1" ind2="0">
<subfield code="a">Control over the Nile

No value xml :
<datafield tag="245" ind1="1" ind2="0">
<subfield code="a">

or sometimes it won't exist:

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Marc A. Brown · Accepted Answer · 2011-05-06T06:18:00

Solution 1

Can you use String.IsNullOrEmpty(String)?

EDIT: Or, you could use Is Nothing to check, as in:

If Num90 Is Nothing Then
  Num90=String.Empty
End If

Posted 6-May-11 6:18am

Marc A. Brown

Updated 6-May-11 6:58am

v2

Comments

stopete82 6-May-11 12:53pm

Thanks for the response but that won't worked because the fallowing code if their is now value for Num090 I get a exception error. This variable doesn't return an string.

Dim Num090 = (From datafield In ser.Descendants("datafield") Where (datafield.Attribute("tag").Value = "090")
Select datafield.Elements.ElementAt(0))

Marc A. Brown 6-May-11 12:56pm

Ok, how about an Is Nothing check? If Num90 Is Nothing Then ... I'll also add this to the answer.

stopete82 6-May-11 14:16pm

yes that's what I am having problems. I would like to check if Num090 is null first. How can I dot that? Thanks again.

Marc A. Brown 6-May-11 14:19pm

Check my answer again. I added Is Nothing code there.

stopete82 6-May-11 14:39pm

Sorry I missed that but that worked.

Code that worked:

Dim Num090 = (From datafield In ser.Descendants("datafield") Where (datafield.Attribute("tag").Value = "090")
Select datafield.Elements.ElementAt(0))

If IsNothing(Num090) Then

Num090.Value = String.Empty

MsgBox(Num090.Value)

Else

MsgBox(Num090.Value)

End If

Thanks

Marc A. Brown 6-May-11 14:41pm

You're quite welcome. Don't forget to accept the answer/vote for it if it helped! :)

stopete82 6-May-11 14:56pm

To accept the answer, do I click on the green "Accept Solution" button?

Marc A. Brown 6-May-11 14:59pm

That sounds correct.

stopete82 6-May-11 15:02pm

I did and the button turned red "Reject solution". I hope that's correct.

Marc A. Brown 6-May-11 15:06pm

Yup, you got it. Thanks! Glad I could help you.