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XmlResolver Class

Resolves external XML resources named by a Uniform Resource Identifier (URI).

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

public abstract class XmlResolver

The XmlResolver type exposes the following members.

  NameDescription
Protected methodSupported by Silverlight for Windows PhoneSupported by Xbox 360XmlResolverInitializes a new instance of the XmlResolver class.
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  NameDescription
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360Equals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows PhoneSupported by Xbox 360FinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetEntityWhen overridden in a derived class, maps a URI to an object containing the actual resource.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360GetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows PhoneSupported by Xbox 360MemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360ResolveUriWhen overridden in a derived class, resolves the absolute URI from the base and relative URIs.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360SupportsTypeThis method adds the ability for the resolver to return other types than just Stream.
Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360ToStringReturns a string that represents the current object. (Inherited from Object.)
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XmlResolver is used to resolve external XML resources, such as entities or document type definitions (DTDs).

Security Considerations

Consider the following items when working with the XmlResolver class.

  • XmlResolver objects can contain sensitive information such as user credentials. You should be careful when caching XmlResolver objects and should not pass the XmlResolver object to an untrusted component.

  • If you are designing a class property that uses the XmlResolver class, the property should be defined as a write-only property. The property can be used to specify the XmlResolver to use, but it cannot be used to return an XmlResolver object.

  • If your application accepts XmlResolver objects from untrusted code, you cannot assume that the URI passed into the GetEntity method will be the same as that returned by the ResolveUri method. Classes derived from the XmlResolver class can override the GetEntity method and return data that is different than what was contained in the original URI.

  • Your application can mitigate memory Denial of Service threats to the GetEntity method by implementing a wrapping implemented IStream that limits the number of bytes read. This helps to guard against situations where malicious code attempts to pass an infinite stream of bytes to the GetEntity method.

The following example preloads the DTDs and entities defined in XHTML 1.0 by setting Xhtml10 on the XmlPreloadedResolver. In this example, the XHTMLPage.html file is a part of the application's XAP package; therefore, we have to pass a fallback resolver to the constructor of the XmlPreloadedResolver.



XmlReaderSettings settings = new XmlReaderSettings();
settings.DtdProcessing = DtdProcessing.Parse;
settings.XmlResolver =
    new XmlPreloadedResolver(new XmlXapResolver(),
        XmlKnownDtds.Xhtml10);

using (XmlReader reader = XmlReader.Create("HTMLPage.html", settings))
{
XDocument document = XDocument.Load(reader);
OutputTextBlock.Text = document.ToString();
}


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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