Question

ReadXML causes FormatException if a numeric value is null

Asked by: Hattl

Hello,

I want to read data from an xml ("XmlFile.xml"). The schema is defined with a schema file that contains following entry.

<xs:element name="SORT_ORDER" type="xs:decimal" minOccurs="0" default="0"/>

Dim Table As DataTable
Table = New DataTable

Table.ReadXmlSchema("Schema.xml")
Table.ReadXml("XmlFile.xml")

This works well, as long "SORT_ORDER" contains a value. But if the tag <SORT_ORDER> is empty I get an
FormatException "Input string was not in a correct format"

I thought I could avoid this by 'default="0", but obviously this isn't the case.
What have I to do, that the ReadXML method can handle empty (null) numeric values in the xml file. (Translate them to "0")

The DataTable "Table" is defined the right way after reading the "Schema.xml": If in the schema file, there is an entry 'default="0"', the default value of the DataColumn "SORT_ORDER" is set to "0D" (Decimal). If not the default vaue is set to "System.DBNull". (as expected)

Thank you very much

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Asked On
2009-09-17 at 04:49:20ID24739442
Tags

.NET XML ReadXML FormatException

Topics

C# Programming Language

,

.NET

,

Extensible Markup Language (XML)

Participating Experts
2
Points
500
Comments
6

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Answers

 

by: MogalManicPosted on 2009-09-18 at 06:24:04ID: 25365632

I think the problem is an empty element (e.g. <SORT_ORDER/> or <SORT_ORDER></SORT_ORDER>) is interpreted as "" which is not of type decimal.  To test this, try changing the type to string and see what the value is.

 

by: HattlPosted on 2009-09-18 at 06:46:55ID: 25365867

Thank you for your answer MogalManic.
Yes, exactly as I described in my question, the problem is an empty element for a decimal type. And the problem would not occure, if the element is of type "string".
My hope was to avoid the uggly workarounds: e.g. to define all fields of the XML as "string" and then iterate through the whole XML and checking each value.

To reformulate my question:
Is it possible with .NET to read a XML file without getting a FormatException under following conditions:
a) There is a schema file for reading the respective XML, which defines some fields as numeric types (e.g. decimal, int)
b) The XML file may contain empty elements for numeric fields

 

by: jensfiedererPosted on 2009-09-18 at 08:14:40ID: 25366820

 

by: HattlPosted on 2009-09-22 at 01:06:39ID: 25390485

Sorry for answering so late to your tip jensfiederer, but I was out of office the last days.
"nilable" works, but only if i add "nil=true" to each tag in the XML containing a null value. But to forget add "nil=true" to a tag with no values has the same effect as to forget to add "0", if the value isn´t needed and is even more effort.
So the problem remains: It seems it is not possible to left tags for numeric values simply blank.
But knowing there is no solution for a problem is also a solution. So I hope it is according the conventions in this comunity, to wait for another 2 or 3 days (if there is yeat again a solution) and then credit the points to you jensfiederer.  TY

 

by: MogalManicPosted on 2009-09-22 at 05:37:24ID: 25392050

You could also write a function to make sure all attributes have the nil='true' attribute.  Somthing like this:


//Note:this is pseudocode and may not be EXACTLY correct
foreach(XmlNode node in doc.SelectNodes("//*[string-length(self::node())=0]") {  //Select all empty nodes
  if (node.Attributes["nil"]==null) { //no nill attribute
     node.Attributes["nil"]=true;
  }
}

                                              
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by: jensfiedererPosted on 2009-09-22 at 07:27:26ID: 25393165

Have you tried applying the nillable to the element definition in the SCHEMA rather than the document?

20120131-EE-VQP-002

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