How to: Customize the Generation of Service Descriptions and Proxy Classes

Article
02/13/2011

This topic is specific to a legacy technology. XML Web services and XML Web service clients should now be created using Windows Communication Foundation.

The following code example is an SDFE that extends the service description and proxy generation processes to include details about a YML SOAP extension.

Example

Imports System
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; it is
' called during the service description generation process.
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 Web service 
        ' method, adds 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; it is called when
' a proxy class is generated for each 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.
Public Class YMLImporter
    Inherits SoapExtensionImporter
    Public Overrides Sub ImportMethod(ByVal metadata As _
                           CodeAttributeDeclarationCollection)
      Dim importer As SoapProtocolImporter = ImportContext
      ' Checks 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 applies 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; it is the
' class that is serialized into XML and 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 = "https://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 System;
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; it is
// called during the service description generation process.
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 Web service
    // method, adds 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; it is called when
// a proxy class is generated for each 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.
public class YMLImporter : SoapExtensionImporter 
{
  public override void ImportMethod(CodeAttributeDeclarationCollection
                                    metadata)
 {
    SoapProtocolImporter importer = ImportContext;
   // Checks 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 applies 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; it is the
// class that is serialized into XML and 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 = "https://www.contoso.com/yml";

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

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How to: Customize the Generation of Service Descriptions and Proxy Classes

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