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XmlTextReader.XmlResolver Property

Sets the XmlResolver used for resolving DTD references.

Namespace:  System.Xml
Assembly:  System.Xml (in System.Xml.dll)

public XmlResolver XmlResolver { set; }

Property Value

Type: System.Xml.XmlResolver
The XmlResolver to use. If set to null, external resources are not resolved.
In version 1.1 of the .NET Framework, the caller must be fully trusted in order to specify an XmlResolver.


Starting with the .NET Framework 2.0, we recommend that you create XmlReader instances by using the XmlReader.Create method to take advantage of new functionality.

The reader uses XmlResolver to resolve the location of the file loaded into the reader and also to resolve DTD references. For example, if your XML included the DOCTYPE declaration, <!DOCTYPE book SYSTEM book.dtd> the reader resolves this external file and ensures that the DTD is well-formed. The reader does not use the DTD for validation.

This property can be changed at any time and takes effect on the next read operation. If this property is set to null, any external DTD references encountered by the reader are not resolved.

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 reader 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.

The following example uses the XmlResolver property to specify the credentials necessary to access the networked file.

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

public class Sample {

  public static void Main() {

    // Create the reader.
    XmlTextReader reader = new XmlTextReader("http://myServer/data/books.xml");

    // Supply the credentials necessary to access the Web server.
    XmlUrlResolver resolver = new XmlUrlResolver();
    resolver.Credentials = CredentialCache.DefaultCredentials;
    reader.XmlResolver = resolver;

    // Parse the file. 
    while (reader.Read()) {
       // Do any additional processing here.

    // Close the reader.


.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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