XmlDocument.XmlResolver Property

Reference

Definition

Namespace:: System.Xml

Assemblies:: netstandard.dll, System.Xml.ReaderWriter.dll

Assembly:: System.Xml.ReaderWriter.dll

Assembly:: System.Xml.dll

Assembly:: netstandard.dll

Source:: XmlDocument.cs

Source:: XmlDocument.cs

Source:: XmlDocument.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Sets the XmlResolver to use for resolving external resources.

public:
 virtual property System::Xml::XmlResolver ^ XmlResolver {  void set(System::Xml::XmlResolver ^ value); };

public virtual System.Xml.XmlResolver? XmlResolver { set; }

public virtual System.Xml.XmlResolver XmlResolver { set; }

member this.XmlResolver : System.Xml.XmlResolver

Public Overridable Property XmlResolver As XmlResolver

Property Value

XmlResolver

The XmlResolver to use.

In version 1.1 of the.NET Framework, the caller must be fully trusted in order to specify an XmlResolver.

Exceptions

XmlException

This property is set to null and an external DTD or entity is encountered.

Examples

The following example loads an XML document which includes a reference to a DTD file. The XmlResolver property is used to set the credentials necessary to access the network resource.

#using <System.dll>
#using <System.Xml.dll>

using namespace System;
using namespace System::IO;
using namespace System::Xml;
using namespace System::Net;
int main()
{
   
   // Supply the credentials necessary to access the DTD file stored on the network.
   XmlUrlResolver^ resolver = gcnew XmlUrlResolver;
   resolver->Credentials = CredentialCache::DefaultCredentials;
   
   // Create and load the XmlDocument.
   XmlDocument^ doc = gcnew XmlDocument;
   doc->XmlResolver = resolver; // Set the resolver.
   doc->Load( "book5.xml" );
   
   // Display the entity replacement text which is pulled from the DTD file.
   Console::WriteLine( doc->DocumentElement->LastChild->InnerText );
}

using System;
using System.IO;
using System.Xml;
using System.Net;

public class Sample {

  public static void Main() {

    // Supply the credentials necessary to access the DTD file stored on the network.
    XmlUrlResolver resolver = new XmlUrlResolver();
    resolver.Credentials = CredentialCache.DefaultCredentials;

    // Create and load the XmlDocument.
    XmlDocument doc = new XmlDocument();
    doc.XmlResolver = resolver;  // Set the resolver.
    doc.Load("book5.xml");

    // Display the entity replacement text which is pulled from the DTD file.
    Console.WriteLine(doc.DocumentElement.LastChild.InnerText);
  }
} // End class

Imports System.IO
Imports System.Xml
Imports System.Net

public class Sample 

  public shared sub Main()

    ' Supply the credentials necessary access the DTD file stored on the network.
    Dim resolver as XmlUrlResolver = new XmlUrlResolver()
    resolver.Credentials = CredentialCache.DefaultCredentials

    ' Create and load the XmlDocument.
    Dim doc as XmlDocument = new XmlDocument()
    doc.XmlResolver = resolver  ' Set the resolver.
    doc.Load("book5.xml")

    ' Display the entity replacement text which is pulled from the DTD file.
    Console.WriteLine(doc.DocumentElement.LastChild.InnerText)
  
  end sub
end class

The example uses the following data files as input.

book5.xml

XML

<!DOCTYPE book SYSTEM 'http://myServer/data/books.dtd'>
<book ISBN = '1-861001-57-5'>
  <title>Oberon's Legacy</title>
  <price>19.95</price>
  <misc>&h;</misc>
</book>

books.dtd

XML

<!ELEMENT book (title,price,misc)> 
<!ATTLIST book 
   genre CDATA "novel"
   ISBN CDATA #REQUIRED>
<!ELEMENT title (#PCDATA)>
<!ELEMENT price (#PCDATA)>
<!ELEMENT misc (#PCDATA)>
<!ENTITY h "hardcover">
<!ENTITY p "paperback">

Remarks

The XmlResolver can be used to load DTDs or expand entity references. Using the XmlResolver.Credentials property, you can set credentials on the XmlResolver to access resources stored on a secure network resource.

If the document was not loaded using an XmlReader (that is, if it was loaded using a stream, file, and so on) the XmlResolver on the XmlDocument is always used.
If the document was loaded with an XmlTextReader, the resolver on the XmlTextReader is used to resolve any DTD references in the DocumentType node. The resolver on the XmlDocument is used to expand any entity references.
If the document was loaded with an XmlValidatingReader, the resolver on the XmlDocument is never used.
If the document was loaded with a class that extends XmlReader and the XmlReader cannot resolve entities (CanResolveEntity returns false), the XmlResolver on the XmlDocument is used to resolve any references in the DocumentType node and to expand any entity references.

Anteckning

If the XmlDocument is loaded using an XmlReader which had an XmlResolver set to it, the XmlResolver on the XmlReader is not cached by the XmlDocument after Load completes.

In version 1.1 of the.NET Framework, if this property is not set, the trust level of the application determines the default behavior.

Fully trusted code: The document uses a default XmlUrlResolver with no user credentials. If authentication is required to access a network resource, use the XmlResolver property to specify an XmlResolver with the necessary credentials.

Semi-trusted code: The XmlResolver property is set to null. External resources are not resolved.

For more information on security and the XmlResolver property, see Resolving External Resources.

This property is a Microsoft extension to the Document Object Model (DOM).

Applies to

Produkt	Versioner
.NET	Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9, 10
.NET Framework	1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard	2.0, 2.1

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