Ling to XML(Literals): implicit Type Conversion ?

Question

Hi,

i have a small problem with Linq to XML:
The following lines are written with VB 2008 / .Net 3.5

Code Snippet

Option Strict On
Imports http://mytarget.sample.com/linq2xml">
Imports System.Xml.Linq
Imports System.Xml
Imports System.Linq

Module Module1

    Sub Main()

        Dim mytest = <?xml version="1.0" encoding="utf-8"?>
                     <myroot xmlns="http://mytarget.sample.com/linq2xml">
                         <Sample MyAttribute="12">This is a Test</Sample>
                         <numVal>12</numVal>
                     </myroot>                    

        Dim myAttr = From myxml In mytest.<myroot> _
                     Where myxml.<numVal>.Value = 12   ' this is the Error-Line
        'Where myxml.<Sample>.@MyAttribute = 12

    End Sub

End Module

 

 

i get the error message "Option Strict On disallows implicit conversions from 'String' to 'Double'"
at "Where myxml.<numVal>.Value = 12". I get the same error in the line "Where myxml.<Sample>.@MyAttribute = 12".

 

This is the generated XSD File

 

Code Snippet

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://mytarget.sample.com/linq2xml" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="myroot">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Sample">
          <xs:complexType>
            <xs:simpleContent>
              <xs:extension base="xs:string">
                <xs:attribute name="MyAttribute" type="xs:unsignedByte" use="required" />
              </xs:extension>
            </xs:simpleContent>
          </xs:complexType>
        </xs:element>
        <xs:element name="numVal" type="xs:unsignedByte" />
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

 

 

Intellisense works fine with this, but there is no implicit Type-Conversion from String to integer/unsignedByte.

best regards,
Andreas B

Answer 1

@attributeName is always a string. And the Value property (of XElement or XAttribute) is also always a string.

You can however cast an XElement itself to some CLR types respectively the VB.NET equivalent, for instance an Integer:

Code Snippet

Dim myAttr = From myxml In mytest.<myroot> _

Where CType(myxml.<numVal>(0), Integer) = 12

 

 

See http://msdn.microsoft.com/en-us/library/system.xml.linq.xelement.op_explicit.aspx for the conversions that are possible.

 

There is also an experimental XSD to LINQ project http://blogs.msdn.com/xmlteam/archive/2008/02/21/linq-to-xsd-alpha-0-2.aspx but that is not part of the .NET framework SDK.