SoapExtension Class

The base class for SOAP extensions for XML Web services created using ASP.NET.

System.Object
  System.Web.Services.Protocols.SoapExtension

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

'Declaration
Public MustInherit Class SoapExtension

The SoapExtension type exposes the following members.

  NameDescription
Protected methodSoapExtensionInitializes a new instance of the SoapExtension class.
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  NameDescription
Public methodChainStreamWhen overridden in a derived class, allows a SOAP extension access to the memory buffer containing the SOAP request or response.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
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 methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetInitializer(Type)When overridden in a derived class, allows a SOAP extension to initialize data specific to a class implementing an XML Web service at a one time performance cost.
Public methodGetInitializer(LogicalMethodInfo, SoapExtensionAttribute)When overridden in a derived class, allows a SOAP extension to initialize data specific to an XML Web service method using an attribute applied to the XML Web service method at a one time performance cost.
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodInitializeWhen overridden in a derived class, allows a SOAP extension to initialize itself using the data cached in the GetInitializer method.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodProcessMessageWhen overridden in a derived class, allows a SOAP extension to receive a SoapMessage to process at each SoapMessageStage.
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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ASP.NET allows a SOAP-related infrastructure to be built by means of an extensibility mechanism. The ASP.NET SOAP extension architecture revolves around an extension that can inspect or modify a message at specific stages in message processing on either the client or the server.

ASP.NET SOAP extensions derive from the SoapExtension class. The GetInitializer and Initialize methods provide alternative mechanisms for initializing the SOAP extension to enhance performance. ProcessMessage is the heart of most SOAP extensions, as the method is called at each stage defined in SoapMessageStage, allowing the SOAP extension to perform the desired behavior of that specific SOAP extension. For SOAP extensions that need to modify the SOAP request or SOAP response, ChainStream provides an opportunity to receive the proposed data to be sent across the wire.

The following TraceExtension SOAP extension outputs the SOAP request and SOAP response to a specified file when applied to an XML Web service method. If the following SOAP extension is installed to run with an XML Web service, the ASPNET user account must have permission to write to the directory in which the log file is written.

Imports System
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.IO

' Define a SOAP Extension that traces the SOAP request and SOAP response 
' for the XML Web service method the SOAP extension is applied to. 
Public Class TraceExtension
    Inherits SoapExtension

    Private oldStream As Stream
    Private newStream As Stream
    Private m_filename As String 

    ' Save the Stream representing the SOAP request or SOAP response into 
    ' a local memory buffer. 
    Public Overrides Function ChainStream(ByVal stream As Stream) As Stream
        oldStream = stream
        newStream = New MemoryStream()
        Return newStream
    End Function 

    ' When the SOAP extension is accessed for the first time, the XML Web 
    ' service method it is applied to is accessed to store the file 
    ' name passed in, using the corresponding SoapExtensionAttribute.     
    Public Overloads Overrides Function GetInitializer(ByVal methodInfo As _
        LogicalMethodInfo, _
    ByVal attribute As SoapExtensionAttribute) As Object 
        Return CType(attribute, TraceExtensionAttribute).Filename
    End Function 

    ' The SOAP extension was configured to run using a configuration file 
    ' instead of an attribute applied to a specific XML Web service 
    ' method.  Return a file name based on the class implementing the Web 
    ' Service's type. 
    Public Overloads Overrides Function GetInitializer(ByVal WebServiceType As _
      Type) As Object 
        ' Return a file name to log the trace information to, based on the 
        ' type. 
        Return "C:\" + WebServiceType.FullName + ".log" 
    End Function 

    ' Receive the file name stored by GetInitializer and store it in a 
    ' member variable for this specific instance. 
    Public Overrides Sub Initialize(ByVal initializer As Object)
        m_filename = CStr(initializer)
    End Sub 

    ' If the SoapMessageStage is such that the SoapRequest or SoapResponse 
    ' is still in the SOAP format to be sent or received over the network, 
    ' save it out to file. 
    Public Overrides Sub ProcessMessage(ByVal message As SoapMessage)
        Select Case message.Stage
            Case SoapMessageStage.BeforeSerialize
            Case SoapMessageStage.AfterSerialize
                WriteOutput(message)
            Case SoapMessageStage.BeforeDeserialize
                WriteInput(message)
            Case SoapMessageStage.AfterDeserialize
        End Select 
    End Sub 

    ' Write the SOAP message out to a file. 
    Public Sub WriteOutput(ByVal message As SoapMessage)
        newStream.Position = 0
        Dim fs As New FileStream(m_filename, FileMode.Append, _
                                 FileAccess.Write)
        Dim w As New StreamWriter(fs)
        w.WriteLine("-----Response at " + DateTime.Now.ToString())
        w.Flush()
        Copy(newStream, fs)
        w.Close()
        newStream.Position = 0
        Copy(newStream, oldStream)
    End Sub 

    ' Write the SOAP message out to a file. 
    Public Sub WriteInput(ByVal message As SoapMessage)
        Copy(oldStream, newStream)
        Dim fs As New FileStream(m_filename, FileMode.Append, _
                                 FileAccess.Write)
        Dim w As New StreamWriter(fs)

        w.WriteLine("----- Request at " + DateTime.Now.ToString())
        w.Flush()
        newStream.Position = 0
        Copy(newStream, fs)
        w.Close()
        newStream.Position = 0
    End Sub 

    Sub Copy(ByVal fromStream As Stream, ByVal toStream As Stream)
        Dim reader As New StreamReader(fromStream)
        Dim writer As New StreamWriter(toStream)
        writer.WriteLine(reader.ReadToEnd())
        writer.Flush()
    End Sub 
End Class 

' Create a SoapExtensionAttribute for our SOAP Extension that can be 
' applied to an XML Web service method.
<AttributeUsage(AttributeTargets.Method)> _
Public Class TraceExtensionAttribute
    Inherits SoapExtensionAttribute

    Private m_filename As String = "c:\log.txt" 
    Private m_priority As Integer 

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

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

    Public Property Filename() As String 
        Get 
            Return m_filename
        End Get 
        Set(ByVal Value As String)
            m_filename = value
        End Set 
    End Property 
End Class

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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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