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XmlFormatExtensionPointAttribute Class

Specifies the XML namespace and XML namespace prefix to use for a service description format extension within a service description. This class cannot be inherited.

System.Object
  System.Attribute
    System.Web.Services.Configuration.XmlFormatExtensionPointAttribute

Namespace:  System.Web.Services.Configuration
Assembly:  System.Web.Services (in System.Web.Services.dll)

[AttributeUsageAttribute(AttributeTargets.Class)]
public sealed class XmlFormatExtensionPointAttribute : Attribute

The XmlFormatExtensionPointAttribute type exposes the following members.

  NameDescription
Public methodXmlFormatExtensionPointAttributeInitializes a new instance of the XmlFormatExtensionPointAttribute class.
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  NameDescription
Public propertyAllowElementsGets or sets a value that indicates whether the member of the class that implements the service description format extension specified in the MemberName property can accept raw XML elements.
Public propertyMemberNameSpecifies that the member of the class that implements the service description format extension can have a service description format extension associated with it.
Public propertyTypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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  NameDescription
Public methodEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeWhen overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)
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A service description format extension extends how a service description is generated for an XML Web service created using ASP.NET. Specifically, a service description format extension adds XML elements to the service description. This is useful when a SOAP extension is built to run on both the client and server side of an XML Web service, as information about SOAP extensions is not automatically placed in the service description. If you add information about the SOAP extension to the service description, a client can thus interpret that it must run the specific SOAP extension. An example of a SOAP extension that must run on both the client and server is an encryption SOAP extension. If an encryption SOAP extension runs on only the server, and it encrypts return values before sending them back to the client, the client must have the SOAP extension running to decrypt the SOAP message. Otherwise, the client cannot process the return value.

Use the following steps to build a service description format extension:

  1. Build a class that derives from ServiceDescriptionFormatExtension.

  2. Apply a XmlFormatExtensionAttribute to the class and specify the extension points at which the service description format extension should run.

  3. Optionally, apply a XmlFormatExtensionPointAttribute to the class and specify a member within the class to act as a new extension point.

  4. Optionally, apply a XmlFormatExtensionPrefixAttribute to the class and specify the XML namespace prefix to be associated with XML elements generated by the service description format extension.

  5. Configure the service description format extension to run within the serviceDescriptionFormatExtensionTypes section of the configuration file.


using System;
using System.Security.Permissions;
using System.CodeDom;
using System.IO;
using System.Text;
using System.Web.Services.Configuration;
using System.Web.Services.Description;
using System.Web.Services.Protocols;
using System.Xml.Serialization;


// The YMLAttribute allows a developer to specify that the YML SOAP
// extension run on a per-method basis.  The Disabled property
// turns reversing the XML on and off. 

[AttributeUsage(AttributeTargets.Method, AllowMultiple=false)]
public class YMLAttribute : SoapExtensionAttribute {
    int priority = 0;
    bool disabled = false;

    public YMLAttribute() : this(false) {}
    public YMLAttribute(bool disabled) 
    {
        this.disabled = disabled;
    }

    public override Type ExtensionType 
    {
        get { return typeof(YMLExtension); }
    }
    public override int Priority 
    {
        get { return priority; }
        set { priority = value; }
    }

    public bool Disabled 
    { 
        get { return disabled; }
        set { disabled = value; }
    }
}

public class YMLExtension : SoapExtension {
    bool disabled = false;
    Stream oldStream;
    Stream newStream;

    public override object GetInitializer(LogicalMethodInfo methodInfo, 
        SoapExtensionAttribute attribute) 
    {
        YMLAttribute attr = attribute as YMLAttribute;
        if (attr != null) return attr.Disabled;
        return false;
    }

    public override object GetInitializer(Type serviceType) 
    {
        return false;
    }

    public override void Initialize(object initializer) 
    {
        if (initializer is Boolean) disabled = (bool)initializer;
    }

    public override Stream ChainStream(Stream stream) 
    {
        if (disabled) return base.ChainStream(stream);
        oldStream = stream;
        newStream = new MemoryStream();
        return newStream;
    }

    public override void ProcessMessage(SoapMessage message) 
    {
        if (disabled) return;
        switch (message.Stage) 
        {
        case SoapMessageStage.BeforeSerialize:
            Encode(message);
            break;
        case SoapMessageStage.AfterSerialize:
            newStream.Position = 0;
            Reverse(newStream, oldStream);
            break;
        case SoapMessageStage.BeforeDeserialize:
            Decode(message);
            break;
        case SoapMessageStage.AfterDeserialize:
            break;
        }
    }        

    void Encode(SoapMessage message) 
    {
        message.ContentType = "text/yml";
    }

    void Decode(SoapMessage message) 
    {
        if (message.ContentType != "text/yml") 
            throw new Exception(
                "invalid content type:" + message.ContentType);
        Reverse(oldStream, newStream);
        newStream.Position = 0;
        message.ContentType = "text/xml";
    }

    void Reverse(Stream from, Stream to) 
    {
        TextReader reader = new StreamReader(from);
        TextWriter writer = new StreamWriter(to);
        string line;
        while ((line = reader.ReadLine()) != null) 
        {
            StringBuilder builder = new StringBuilder();
            for (int i = line.Length - 1; i >= 0; i--) 
            {
                builder.Append(line[i]);
            }
            writer.WriteLine(builder.ToString());
        }
        writer.Flush();
    }
}
// The YMLReflector class is part of the YML SDFE, as it is
// called during the service description generation process.
[PermissionSet(SecurityAction.Demand, Name="FullTrust")]
public class YMLReflector : SoapExtensionReflector 
{
    public override void ReflectMethod() 
    {
        ProtocolReflector reflector = ReflectionContext;
        YMLAttribute attr = 
            (YMLAttribute)reflector.Method.GetCustomAttribute(
            typeof(YMLAttribute));
        // If the YMLAttribute has been applied to this XML Web service 
        // method, add the XML defined in the YMLOperationBinding class.
        if (attr != null) 
        {
            YMLOperationBinding yml = new YMLOperationBinding();
            yml.Reverse = !(attr.Disabled);
            reflector.OperationBinding.Extensions.Add(yml);
        }
    }
}



// The YMLImporter class is part of the YML SDFE, as it is called when a
// proxy class is generated for each XML Web service method the proxy class
// communicates with. The class checks whether the service description
// contains the XML that this SDFE adds to a service description. If it 
// exists, then the YMLExtension is applied to the method in the proxy class.
[PermissionSet(SecurityAction.Demand, Name="FullTrust")]
public class YMLImporter : SoapExtensionImporter 
{
    public override void ImportMethod(
        CodeAttributeDeclarationCollection metadata) 
    {
        SoapProtocolImporter importer = ImportContext;
        // Check whether the XML specified in the YMLOperationBinding 
        // is in the service description.
        YMLOperationBinding yml = 
           (YMLOperationBinding)importer.OperationBinding.Extensions.Find(
           typeof(YMLOperationBinding));
        if (yml != null)
        {
            // Only apply the YMLAttribute to the method when the XML should
            // be reversed.
            if (yml.Reverse)
            {
                CodeAttributeDeclaration attr = 
                    new CodeAttributeDeclaration(typeof(YMLAttribute).FullName);
                attr.Arguments.Add(
                    new CodeAttributeArgument(new CodePrimitiveExpression(true)));
                metadata.Add(attr);
            }
        }
    }
}

// The YMLOperationBinding class is part of the YML SDFE, as it is the
// class that is serialized into XML and is placed in the service
// description.
[XmlFormatExtension("action", YMLOperationBinding.YMLNamespace, 
    typeof(OperationBinding))]
[XmlFormatExtensionPrefix("yml", YMLOperationBinding.YMLNamespace)]
public class YMLOperationBinding : ServiceDescriptionFormatExtension 
{
    private Boolean reverse;

    public const string YMLNamespace = "http://www.contoso.com/yml";

    [XmlElement("Reverse")]
    public Boolean Reverse 
    {
        get { return reverse; }
        set { reverse = value; }
    }
}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

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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