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XmlFormatExtensionPrefixAttribute 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.

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

'Declaration
<AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple := True)> _
Public NotInheritable Class XmlFormatExtensionPrefixAttribute _
	Inherits Attribute
'Usage
Dim instance As XmlFormatExtensionPrefixAttribute

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 placed in the service description. If you add information about the SOAP extension to the service description, a client can 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 an XmlFormatExtensionAttribute to the class and specify the extension points at which the service description format extension should run.

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

  4. Optionally, apply an 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.

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

' 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
    Inherits SoapExtensionAttribute
    Dim _priority As Integer = 0
    Dim _disabled As Boolean = False 

    Public Sub New()
        Me.New(False)
    End Sub 

    Public Sub New(ByVal Disabled As Boolean)
        _disabled = Disabled
    End Sub 

    Public Overrides ReadOnly Property ExtensionType() As Type
        Get 
            Return GetType(YMLExtension)
        End Get 
    End Property 

    Public Overrides Property Priority() As Integer 
        Get 
            Return _priority
        End Get 
        Set(ByVal Value As Integer)
            _priority = Value
        End Set 
    End Property 

    Public Property Disabled() As Boolean 
        Get 
            Return _disabled
        End Get 
        Set(ByVal Value As Boolean)
            _disabled = Value
        End Set 
    End Property 
End Class 

Public Class YMLExtension
    Inherits SoapExtension
    Dim _disabled As Boolean = False 
    Dim oldStream As Stream
    Dim newStream As Stream

    Public Overloads Overrides Function GetInitializer( _
        ByVal methodInfo As LogicalMethodInfo, _
        ByVal attribute As SoapExtensionAttribute) As Object

        Dim attr As YMLAttribute = attribute
        If (Not attr Is Nothing) Then 
            Return attr.Disabled
        End If 
        Return False 
    End Function 

    Public Overloads Overrides Function GetInitializer( _
        ByVal WebServiceType As Type) As Object
        Return False 
    End Function 

    Public Overrides Sub Initialize(ByVal initializer As Object)
        If (TypeOf initializer Is Boolean) Then
            _disabled = CBool(initializer)
        End If 
    End Sub 

    Public Overrides Function ChainStream(ByVal streamref As Stream) As Stream
        If (_disabled) Then 
            Return CType(Me, SoapExtension).ChainStream(streamref)
        End If
        oldStream = streamref
        newStream = New MemoryStream()
        Return newStream
    End Function 

    Public Overrides Sub ProcessMessage(ByVal message As SoapMessage)
        If (_disabled) Then Return 
        Select Case (message.Stage)
            Case SoapMessageStage.BeforeSerialize
                Encode(message)
            Case SoapMessageStage.AfterSerialize
                newStream.Position = 0
                Reverse(newStream, oldStream)
            Case SoapMessageStage.BeforeDeserialize
                Decode(message)
            Case SoapMessageStage.AfterDeserialize
        End Select 
    End Sub 

    Sub Encode(ByRef message As SoapMessage)
        message.ContentType = "text/yml" 
    End Sub 

    Sub Decode(ByVal message As SoapMessage)
        If (message.ContentType <> "text/yml") Then 
            Throw New Exception("invalid content type:" & message.ContentType)
        End If
        Reverse(oldStream, newStream)
        newStream.Position = 0
        message.ContentType = "text/xml" 
    End Sub 

    Sub Reverse(ByVal source As Stream, ByVal dest As Stream)
        Dim reader As TextReader = New StreamReader(source)
        Dim writer As TextWriter = New StreamWriter(dest)
        Dim line As String
        line = reader.ReadLine()
        While (Not line Is Nothing)
            writer.WriteLine(StrReverse(line))
            line = reader.ReadLine()
        End While
        writer.Flush()
    End Sub 
End Class 


' 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
    Inherits SoapExtensionReflector
    Public Overrides Sub ReflectMethod()
        Dim reflector As ProtocolReflector = ReflectionContext
        Dim attr As YMLAttribute = _
            reflector.Method.GetCustomAttribute(GetType(YMLAttribute))
        ' If the YMLAttribute has been applied to this XML Web service  
        ' method, add the XML defined in the YMLOperationBinding class. 
        If (Not attr Is Nothing) Then 
            Dim yml As YMLOperationBinding = New YMLOperationBinding()
            yml.Reverse = Not attr.Disabled
            reflector.OperationBinding.Extensions.Add(yml)
        End If 
    End Sub 
End Class 

' 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
    Inherits SoapExtensionImporter
    Public Overrides Sub ImportMethod( _
        ByVal metadata As CodeAttributeDeclarationCollection)
        Dim importer As SoapProtocolImporter = ImportContext
        ' Check whether the XML specified in the YMLOperationBinding is  
        ' in the service description. 
        Dim yml As YMLOperationBinding = _
            importer.OperationBinding.Extensions.Find( _
            GetType(YMLOperationBinding))
        If (Not yml Is Nothing) Then 
            ' Only apply the YMLAttribute to the method when the XML  
            ' should be reversed. 
            If (yml.Reverse) Then 
                Dim attr As CodeAttributeDeclaration = _
                    New CodeAttributeDeclaration(GetType(YMLAttribute).FullName)
                attr.Arguments.Add( _
                    New CodeAttributeArgument(New CodePrimitiveExpression(True)))
                metadata.Add(attr)
            End If 
        End If 
    End Sub 
End Class 

' 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, _
    GetType(OperationBinding)), _
    XmlFormatExtensionPrefix("yml", YMLOperationBinding.YMLNamespace)> _
Public Class YMLOperationBinding
    Inherits ServiceDescriptionFormatExtension
    Private _reverse As Boolean 
    Public Const YMLNamespace As String = "http://www.contoso.com/yml"

    <XmlElement("Reverse")> _
    Public Property Reverse() As Boolean 
        Get 
            Return _reverse
        End Get 
        Set(ByVal Value As Boolean)
            _reverse = Value
        End Set 
    End Property 

End Class
#using <mscorlib.dll>
#using <System.dll>
#using <System.Web.Services.dll>
#using <System.Xml.dll>
using namespace System;
using namespace System::CodeDom;
using namespace System::IO;
using namespace System::Text;
using namespace System::Web::Services::Configuration;
using namespace System::Web::Services::Description;
using namespace System::Web::Services::Protocols;
using namespace System::Xml::Serialization;

public __gc class YMLExtension;

// 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 __gc class YMLAttribute : public SoapExtensionAttribute
{
    int priority;
    bool disabled;

public:
    YMLAttribute() : disabled(false) {
        priority = 0;
        disabled = false;
    }

    YMLAttribute(bool disabled) {
        this->disabled = disabled;
    }

    __property Type* get_ExtensionType() { return __typeof(YMLExtension); }

    __property int get_Priority() { return priority; }
    __property void set_Priority(int value) { priority = value; }

    __property bool get_Disabled() { return disabled; }
    __property void set_Disabled(bool value) { disabled = value; }

};


public __gc class YMLExtension : public SoapExtension {
    bool disabled;
    Stream* oldStream;
    Stream* newStream;

public:
    YMLExtension()
    {
        disabled = false;
    }

    Object* GetInitializer(LogicalMethodInfo* /*methodInfo*/, SoapExtensionAttribute* attribute) {
        YMLAttribute* attr = dynamic_cast<YMLAttribute*>(attribute);
        if (attr != 0) 
            return __box(attr->get_Disabled());
        return __box(false);
    }

    Object* GetInitializer(Type* /*serviceType*/) {
        return __box(false);
    }

    void Initialize(Object* initializer) {
        if (Boolean * pb = dynamic_cast<System::Boolean*>(initializer)) 
            disabled = *pb;
    }

    Stream* ChainStream(Stream* stream) {
        if (disabled) return __super::ChainStream(stream);
        oldStream = stream;
        newStream = new MemoryStream();
        return newStream;
    }

    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 = S"text/yml";
    }

    void Decode(SoapMessage* message) {
        if (String::Compare(message->ContentType, S"text/yml") != 0) 
            throw new Exception(String::Concat(S"invalid content type: {0}",message->ContentType));
        Reverse(oldStream, newStream);
        newStream->Position = 0;
        message->ContentType = S"text/xml";
    }

    void Reverse(Stream* from, Stream* to) {
        TextReader* reader = new StreamReader(from);
        TextWriter* writer = new StreamWriter(to);
        String* line;
        while ((line = reader->ReadLine()) != 0) {
            StringBuilder* builder = new StringBuilder();
            for (int i = line->Length - 1; i >= 0; i--) {
                builder->Append(line->Chars[i]);
            }
            writer->WriteLine(builder);
        }
        writer->Flush();
    }
};


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

public:
    const String* YMLNamespace;
    YMLOperationBinding() : YMLNamespace(S"http://www.contoso.com/yml") {}

    [XmlElement(S"Reverse")]
    __property Boolean get_Reverse() { return reverse; }
    [XmlElement(S"Reverse")]
    __property void set_Reverse(Boolean value) { reverse = value; }
};

// The YMLReflector class is part of the YML SDFE, as it gets
// called during the service description generation process.
public __gc class YMLReflector : public SoapExtensionReflector {
public:
    void ReflectMethod() {
        ProtocolReflector *reflector = ReflectionContext;
        YMLAttribute *attr = dynamic_cast<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 != 0) {
            YMLOperationBinding* yml = new YMLOperationBinding();
            yml->Reverse = !(attr->Disabled);
            reflector->OperationBinding->Extensions->Add(yml);
        }
    }
};

// The YMLImporter class is part of the YML SDFE, as it gets called when
// a proxy class is generated for each XML Web service method the proxy class
// communictes 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.
public __gc class YMLImporter : public SoapExtensionImporter {
public:
    void ImportMethod(CodeAttributeDeclarationCollection *metadata) {
        SoapProtocolImporter *importer = ImportContext;
        // Check whether the XML specified in the YMLOperationBinding is in the
        // service description.
        YMLOperationBinding *yml = dynamic_cast<YMLOperationBinding*>(importer->OperationBinding->Extensions->Find(__typeof(YMLOperationBinding)));
        if (yml != 0) {
            // 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(__box(true))));
                metadata->Add(attr);
            }
        }
    }
};

System.Object
  System.Attribute
    System.Web.Services.Configuration.XmlFormatExtensionPrefixAttribute

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

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

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