Xml Load error - Reference to undeclared entity

Question

I am using below vb.net code to load xml file.

Dim reader As XmlTextReader = New XmlTextReader("D:\file_1.xml")    
   reader.EntityHandling = EntityHandling.ExpandEntities            
   Dim xDoc As XmlDocument = New XmlDocument()          
   xDoc.Load(reader)   

xdoc.load() will give "reference to undeclared entity"
The Input xml file have List of Special character.

Like:<_1 Value="Á"/>
<_2 Value="Â"/>
<_3 Value="â"/>
<_4 Value="´"/>
<_5 Value="Æ"/>

This error can be solved by declaring the entity in the xml file.

<!DOCTYPE doctypeName [
   <!ENTITY Aacute "&#193;">
]> 

Is there any method to load the xml without changing xml using vb.net code?

Answer 1

Hi test code,
Xml doesn't define entities (ie named references to UNICODE characters), so &Acirc, &AElig are not translated to their corresponding character. You need to use the numerical value instead.
Here is a similar thread you can refer to.

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Answer 2

If you cannot modify the original file, then maybe create dynamically a helper file that includes the entity definition and a reference to original file. Something like this:

Dim filename = "D:\file_1.xml"
Dim t = Path.GetTempFileName

File.WriteAllText(t, $"<?xml version='1.0' encoding='utf-8' ?>
<!DOCTYPE xml [
  <!ENTITY Aacute '&#193;'>
  <!-- TODO: add more entities -->
  <!ENTITY otherFile SYSTEM 'file://{filename}'>
]>
<xml>
  &otherFile;
</xml>")

Dim xDoc As XmlDocument = New XmlDocument()

Using reader As XmlTextReader = New XmlTextReader(t)
   reader.EntityHandling = EntityHandling.ExpandEntities
   reader.XmlResolver = New XmlUrlResolver
   xDoc.Load(reader)
End Using

File.Delete(t)

Console.WriteLine(xDoc.OuterXml)

However the loaded document contain a different root node (<xml>).

Use this workaround if it is difficult to find a solution based on some custom entity resolver.