{"id":1380,"date":"2013-07-26T07:14:06","date_gmt":"2013-07-26T07:14:06","guid":{"rendered":"http:\/\/fanzung.com\/?p=1380"},"modified":"2013-08-01T15:11:47","modified_gmt":"2013-08-01T15:11:47","slug":"using-soap-headers","status":"publish","type":"post","link":"https:\/\/dongson.info\/?p=1380","title":{"rendered":"Using SOAP Headers"},"content":{"rendered":"
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Using SOAP Headers<\/h1>\n
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.NET Framework 1.1 <\/strong><\/div>\n
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Communicating with an XML Web service method using SOAP follows a standard format. Part of this format is the data that is encoded in an XML document. The XML document consists of a root Envelope<\/strong> tag, which in turn consists of a required Body<\/strong> element and an optional Header<\/strong> element. The Body<\/strong> element comprises the data specific to the message. The optional Header<\/strong> element can contain additional information not directly related to the particular message. Each child element of the Header<\/strong> element is called a SOAP header.<\/p>\n

Although the SOAP headers can contain data related to the message, as the SOAP specification doesn’t strictly define the contents of a SOAP header, they typically contain information processed by infrastructure within a Web server. An example of how a SOAP header can be used is to supply routing information for the SOAP message within the SOAP header.<\/p>\n

Defining and Processing SOAP Headers<\/h2>\n

XML Web services created using ASP.NET can define and manipulate SOAP headers. Defining a SOAP header is accomplished by defining a class representing the data in a particular SOAP header and deriving it from the SoapHeader<\/a> class.<\/p>\n

To define a class representing a SOAP header<\/strong><\/p>\n

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  1. Create a class deriving from the SoapHeader<\/strong>class with a name matching the root element for the SOAP header.\n
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    C#<\/a><\/div>\n<\/div>\n
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    <\/div>\n
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    public class MyHeader : SoapHeader\r\n[Visual\u00a0Basic]\r\nPublic Class MyHeader : Inherits SoapHeader<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
  2. Add public fields or properties, matching the names and their respective data types for each element in the SOAP header.For instance, given the following SOAP header, the class following it defines a class representing the SOAP header.\n
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    C#<\/a><\/div>\n<\/div>\n
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    public class MyHeader : SoapHeader\r\n{\r\n   public DateTime Created;\r\n   public long Expires;\r\n}\r\n[Visual\u00a0Basic]\r\nPublic Class MyHeader\r\n  Inherits SoapHeader\r\n    Public Created As DateTime\r\n    Public Expires As Long\r\nEnd Class<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n<\/ol>\n
    To process SOAP headers within an XML Web service<\/strong><\/p>\n
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    1. Add a public member to the class implementing the XML Web service of the type representing the SOAP header.\n
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      C#<\/a><\/div>\n<\/div>\n
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      <\/div>\n
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      [WebService(Namespace=\"http:\/\/www.contoso.com\")]\r\npublic class MyWebService\r\n{\r\n    \/\/ Add a member variable of the type deriving from SoapHeader.\r\n    public MyHeader timeStamp;\r\n[Visual\u00a0Basic]\r\n<WebService(Namespace:=\"http:\/\/www.contoso.com\")> _\r\nPublic Class MyWebService\r\n    ' Add a member variable of the type deriving from SoapHeader.\r\n    Public TimeStamp As MyHeader<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
    2. Apply a SoapHeader<\/a> attribute to each XML Web service method that intends to process the SOAP header. Set the MemberName<\/strong> property of the SoapHeader<\/strong>attribute to the name of the member variable created in the first step.\n
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      C#<\/a><\/div>\n<\/div>\n
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      [WebMethod]\r\n[SoapHeader(\"timeStamp\")]\r\npublic void MyWebMethod()\r\n[Visual\u00a0Basic]\r\n<WebMethod, SoapHeader(\"TimeStamp\")> _\r\nPublic Sub MyWebMethod()<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
    3. Within each XML Web service method that the SoapHeader<\/strong>attribute is applied to, access the member variable created in the first step to process the data sent in the SOAP header.\n
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      C#<\/a><\/div>\n<\/div>\n
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      [WebMethod]\r\n[SoapHeader(\"timeStamp\",\r\n            Direction=SoapHeaderDirection.InOut)]\r\npublic string MyWebMethod()\r\n{\r\n  \/\/ Verify that the client sent the SOAP Header.\r\n  if (timeStamp == null)\r\n  {\r\n     timeStamp = new MyHeader();\r\n  }\r\n  \/\/ Set the value of the SoapHeader returned\r\n  \/\/ to the client.\r\n  timeStamp.Expires = 60000;\r\n  timeStamp.Created = DateTime.UtcNow;\r\n\r\n  return \"Hello World\";\r\n}\r\n[Visual\u00a0Basic]\r\n<WebMethod,SoapHeader(\"TimeStamp\", _\r\n                      Direction:=SoapHeaderDirection.InOut)> _\r\nPublic Function MyWebMethod() As String\r\n   ' Verify that the client sent the SOAP Header.\r\n   If (TimeStamp Is Nothing) Then\r\n      TimeStamp = New MyHeader\r\n   End If\r\n\r\n   ' Set the value of the SoapHeader returned\r\n   ' to the client.\r\n   TimeStamp.Expires = 60000\r\n   TimeStamp.Created = DateTime.UtcNow\r\n\r\n   Return \"Hello World\"\r\nEnd Function<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n<\/ol>\n
      The following code example demonstrates how to define and process a SOAP header in an XML Web service created using ASP.NET. The MyWebService<\/code> XML Web service has a member variable named timeStamp<\/code>, which is of a type deriving from SoapHeader<\/strong> (MyHeader<\/code>) and set to the MemberName<\/strong> property of the SoapHeader<\/strong> attribute. In addition, a SoapHeader<\/strong> attribute is applied to the MyWebMethod<\/code> XML Web service method specifying myHeaderMemberVariable<\/code>. Within the MyWebMethod<\/code> XML Web service method, myHeaderMemberVariable<\/code> is accessed to set the value of the Created<\/code> and Expires<\/code> XML elements of the SOAP header.<\/p>\n
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      C#<\/a><\/div>\n<\/div>\n
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      <%@ WebService Language=\"C#\" Class=\"MyWebService\" %>\r\nusing System;\r\nusing System.Web.Services;\r\nusing System.Web.Services.Protocols;\r\n\r\n\/\/ Define a SOAP header by deriving from the SoapHeader class.\r\npublic class MyHeader : SoapHeader\r\n{\r\n   public DateTime Created;\r\n   public long Expires;\r\n}\r\n\r\n[WebService(Namespace=\"http:\/\/www.contoso.com\")]\r\npublic class MyWebService : System.Web.Services.WebService\r\n{\r\n   \/\/ Add a member variable of the type deriving from SoapHeader.\r\n   public MyHeader timeStamp;\r\n\r\n   \/\/ Apply a SoapHeader attribute.\r\n   [WebMethod]\r\n   [SoapHeader(\"timeStamp\", Direction=SoapHeaderDirection.InOut)]\r\n   public string HelloWorld()\r\n   {\r\n      if (timeStamp == null)\r\n         timeStamp = new MyHeader();\r\n\r\n      timeStamp.Expires = 60000;\r\n      timeStamp.Created = DateTime.UtcNow;\r\n\r\n      return \"Hello World\";\r\n   }\r\n}\r\n[Visual\u00a0Basic]\r\n<%@ WebService Language=\"VB\" Class=\"MyWebService\" %>\r\nImports System\r\nImports System.Web.Services\r\nImports System.Web.Services.Protocols\r\n\r\n' Define a SOAP header by deriving from the SoapHeader class.\r\nPublic Class MyHeader\r\n    Inherits SoapHeader\r\n    Public Created As DateTime\r\n    Public Expires As Long\r\nEnd Class\r\n\r\n<WebService(Namespace:=\"http:\/\/www.contoso.com\")> _\r\nPublic Class MyWebService\r\n    Inherits System.Web.Services.WebService\r\n\r\n    ' Add a member variable of the type deriving from SoapHeader.\r\n    Public timeStamp As MyHeader\r\n\r\n    ' Apply a SoapHeader attribute.\r\n    <WebMethod(), _\r\n     SoapHeader(\"timeStamp\", Direction:=SoapHeaderDirection.InOut)> _\r\n    Public Function HelloWorld() As String\r\n\r\n        If (timeStamp Is Nothing) Then\r\n            timeStamp = New MyHeader\r\n        End If\r\n\r\n        timeStamp.Expires = 60000\r\n        timeStamp.Created = DateTime.UtcNow\r\n\r\n        Return \"Hello World\"\r\n    End Function\r\nEnd Class<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
      In the previous example, a SOAP response is returned to the client with the Expires<\/code> element set to 60000 (number of milliseconds, so 1 minute) and the Created<\/code> element to the current time in coordinated universal time. That is, the following SOAP response is sent to the client.<\/p>\n
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      <?xml version=\"1.0\" encoding=\"utf-8\"?>\r\n<soap:Envelope xmlns:soap=\"http:\/\/schemas.xmlsoap.org\/soap\/envelope\/\">\r\n  <soap:Header>\r\n    <MyHeader xmlns=\"http:\/\/www.contoso.com\">\r\n      <Created>dateTime<\/Created>\r\n      <Expires>long<\/Expires>\r\n    <\/MyHeader>\r\n  <\/soap:Header>\r\n  <soap:Body>\r\n    <MyWebMethod xmlns=\"http:\/\/www.contoso.com\" \/>\r\n  <\/soap:Body>\r\n<\/soap:Envelope><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
      Building a Client that Processes SOAP Headers<\/h3>\n
      An XML Web services client can send and receive SOAP headers when communicating with an XML Web service. When a proxy class is generated for an XML Web service expecting or returning SOAP headers using the Wsdl.exe utility, the proxy class includes information about the SOAP headers. Specifically, the proxy class has member variables representing the SOAP headers that correlate to those found in the XML Web service. The proxy class also has definitions for the corresponding classes representing the SOAP header. For example, proxy classes generated for the previous XML Web service will have a member variable of type MyHeader<\/code> and a definition for the MyHeader<\/code> class. For details on creating a proxy class, see Creating an XML Web Service Proxy<\/a>.<\/p>\n
      Note: If the XML Web service defines the member variables representing the SOAP headers of type SoapHeader<\/a> or SoapUnknownHeader<\/a> instead of a class deriving from SoapHeader<\/strong>, a proxy class will not have any information about that SOAP header.<\/p>\n
      To process SOAP headers within an XML Web service client<\/strong><\/p>\n
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      1. Create a new instance of the class representing the SOAP header.\n
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        VB<\/a><\/div>\n<\/div>\n
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        Dim mySoapHeader As MyHeader = New MyHeader()\r\n[C#]\r\nMyHeader mySoapHeader = new MyHeader();<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
      2. Populate the values for the SOAP header.\n
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        VB<\/a><\/div>\n<\/div>\n
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        header.Expires = 60000\r\nheader.Created = DateTime.UtcNow\r\n[C#]\r\nheader.Expires = 60000;\r\nheader.Created = DateTime.UtcNow;<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
      3. Create a new instance of the proxy class.\n
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        VB<\/a><\/div>\n<\/div>\n
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        Dim proxy As MyWebService = New MyWebService()\r\n[C#]\r\nMyWebService proxy = new MyWebService();<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
      4. Assign the SOAP header object to the member variable of the proxy class representing the SOAP header.\n
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        VB<\/a><\/div>\n<\/div>\n
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        proxy.MyHeaderValue = mySoapHeader\r\n[C#]\r\nproxy.MyHeaderValue = mySoapHeader<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
      5. Call the method on the proxy class that communicates with the XML Web service method.The SOAP header portion of the SOAP request sent to the XML Web service will include the contents of the data stored in the SOAP header object.\n
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        VB<\/a><\/div>\n<\/div>\n
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        Dim results as String = proxy.MyWebMethod()\r\n[C#]\r\nstring results = proxy.MyWebMethod();<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n<\/ol>\n
        The following code example demonstrates how to pass a SOAP header from a client to an XML Web service.<\/p>\n
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        VB<\/a><\/div>\n<\/div>\n
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        <%@ Page Language=\"VB\" %>\r\n\r\n<asp:Label id=\"ReturnValue\" runat=\"server\" \/>\r\n<script runat=server language=VB>\r\n\r\n Sub Page_Load(o As Object, e As EventArgs)\r\n\r\n  Dim header As MyHeader = New MyHeader()\r\n\r\n  ' Populate the values of the SOAP header.\r\n   header.Expires = 60000\r\n   header.Created = DateTime.UtcNow\r\n\r\n  ' Create a new instance of the proxy class.\r\n  Dim proxy As MyWebService = New MyWebService()\r\n\r\n  ' Add the MyHeader SOAP header to the SOAP request.\r\n  proxy.MyHeaderValue = header\r\n\r\n  ' Call the method on the proxy class that communicates\r\n  ' with your XML Web service method.\r\n  Dim results as String = proxy.MyWebMethod()\r\n\r\n  ' Display the results of the method in a label.\r\n  ReturnValue.Text = results\r\n\r\n End Sub\r\n<\/script>\r\n[C#]\r\n<%@ Page Language=\"C#\" %>\r\n\r\n<asp:Label id=\"ReturnValue\" runat=\"server\" \/>\r\n<script runat=server language=c#>\r\n\r\n void Page_Load(Object o, EventArgs e)\r\n {\r\n\r\n  MyHeader header = new MyHeader();\r\n\r\n  \/\/ Populate the values of the SOAP header.\r\n  header.Expires = 60000;\r\n  header.Created = DateTime.UtcNow;\r\n\r\n  \/\/ Create a new instance of the proxy class.\r\n  MyWebService proxy = new MyWebService();\r\n\r\n  \/\/ Add the MyHeader SOAP header to the SOAP request.\r\n  proxy.MyHeaderValue = header;\r\n\r\n  \/\/ Call the method on the proxy class that communicates\r\n  \/\/ with your XML Web service method.\r\n  string results = proxy.MyWebMethod();\r\n\r\n  \/\/ Display the results of the method in a label.\r\n  ReturnValue.Text = results;\r\n }\r\n<\/script><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
        Changing the SOAP Headers Recipients<\/h3>\n
        By default, SOAP headers are sent by an XML Web service client to an XML Web service method when a SoapHeader<\/strong> attribute is applied to an XML Web service method. However, a SOAP header can also be sent by the XML Web service method back to the XML Web service client. It can also be sent both ways. Setting the Direction<\/strong> property of a SoapHeader<\/strong> attribute applied to an XML Web service method controls the recipient of the SOAP header. The Direction <\/strong>property is of type SoapHeaderDirection<\/strong>, which has four values: In<\/strong>, Out<\/strong>, InOut<\/strong>, and Fault<\/strong>. These refer to the recipient (whether it is the XML Web service server), to the client, or both the XML Web service server and client, and whether the SOAP header is sent to the client when an exception is thrown by the XML Web service, respectively.<\/p>\n
        Note: Version 1.0 of the .NET Framework SDK does not support the Fault<\/strong> value.<\/p>\n
        To change the SOAP header recipient<\/strong><\/p>\n
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        1. Define the SOAP header.\n
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          public class MyHeader : SoapHeader\r\n{\r\n   public DateTime Created;\r\n   public long Expires;\r\n}\r\n[Visual\u00a0Basic]\r\nPublic Class MyHeader\r\n  Inherits SoapHeader\r\n    Public Created As DateTime\r\n    Public Expires As Long\r\nEnd Class<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
        2. Add a member variable to the class implementing the XML Web service.\n
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          [WebService(Namespace=\"http:\/\/www.contoso.com\")]\r\npublic class MyWebService : WebService\r\n{\r\n    public MyHeader myOutHeader;\r\n[Visual\u00a0Basic]\r\n<WebService(Namespace:=\"http:\/\/www.contoso.com\")> _\r\nPublic Class MyWebService\r\n  Inherits WebService\r\n    Public myOutHeader As MyHeader<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
        3. Apply a SoapHeader <\/strong>attribute to each XML Web service method that processes the SOAP header. Set the Direction<\/strong> property to each intended recipient, using the SoapHeaderDirection<\/a> enumeration. The following example sets the XML Web service client as the recipient by setting Direction<\/strong> to SoapHeaderDirection.Out<\/strong>.\n
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              [WebMethod]\r\n    [SoapHeader(\"myOutHeader\",Direction=SoapHeaderDirection.Out)]\r\n[Visual\u00a0Basic]\r\n    <WebMethod, _\r\n     SoapHeader(\"myOutHeader\",Direction:=SoapHeaderDirection.Out)><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
        4. Process or set the SOAP header, depending on the recipient. The following code example sets the values of the SOAP header, as the recipient is the XML Web service client.\n
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          C#<\/a><\/div>\n<\/div>\n
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          \/\/ Set the Time the SOAP message expires.\r\nmyOutHeader.Expires = 60000;\r\nmyOutHeader.Created = DateTime.UtcNow;\r\n[Visual\u00a0Basic]\r\n' Set the Time the SOAP message expires.\r\nmyOutHeader.Expires = 60000\r\nmyOutHeader.Created = DateTime.UtcNow<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n<\/ol>\n
          The following code example defines a MyHeader<\/code> SOAP header that is sent from the XML Web service method to the client.<\/p>\n
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          C#<\/a><\/div>\n<\/div>\n
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          <%@ WebService Language=\"C#\" Class=\"MyWebService\" %>\r\nusing System;\r\nusing System.Web.Services;\r\nusing System.Web.Services.Protocols;\r\n\r\n\/\/ Define a SOAP header by deriving from the SoapHeader class.\r\npublic class MyHeader : SoapHeader\r\n{\r\n   public DateTime Created;\r\n   public long Expires;\r\n} \r\n\r\n[WebService(Namespace=\"http:\/\/www.contoso.com\")]\r\npublic class MyWebService : WebService\r\n{\r\n    public MyHeader myOutHeader;\r\n\r\n    [WebMethod]\r\n    [SoapHeader(\"myOutHeader\",Direction=SoapHeaderDirection.Out)]\r\n    public void MyOutHeaderMethod()\r\n    {\r\n      \/\/ Set the time the SOAP message expires.\r\n      myOutHeader.Expires = 60000;\r\n      myOutHeader.Created = DateTime.UtcNow;\r\n    }\r\n}\r\n[Visual\u00a0Basic]\r\n<%@ WebService Language=\"VB\" Class=\"MyWebService\" %>\r\nImports System\r\nImports System.Web.Services\r\nImports System.Web.Services.Protocols\r\n\r\n' Define a SOAP header by deriving from the SoapHeader class.\r\nPublic Class MyHeader\r\n  Inherits SoapHeader\r\n    Public Created As DateTime\r\n    Public Expires As Long\r\nEnd Class\r\n\r\n<WebService(Namespace:=\"http:\/\/www.contoso.com\")> _\r\nPublic Class MyWebService\r\n  Inherits WebService\r\n    Public myOutHeader As MyHeader \r\n\r\n    <WebMethod, _\r\n     SoapHeader(\"myOutHeader\",Direction:=SoapHeaderDirection.Out)> _\r\n    Public Sub MyOutHeaderMethod()\r\n         ' Set the time the SOAP message expires.\r\n         myOutHeader.Expires = 60000\r\n         myOutHeader.Created = DateTime.UtcNow\r\n    End Sub\r\nEnd Class<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
          Handling Unknown SOAP Headers<\/h3>\n
          An XML Web service client can send a SOAP request with a SOAP header to an XML Web service method that the XML Web service might not have explicitly defined that it was expecting. In this case, it is important to determine whether the semantics of the SOAP header are understood and processed, as the SOAP specification states that an exception is thrown when SOAP headers have a mustUnderstand<\/strong> attribute set to true<\/strong>. For details on handling SOAP headers required by a client, see Handling SOAP Headers Required by an XML Web Service Client<\/a>.<\/p>\n
          To handle unknown SOAP headers from an XML Web service client<\/strong><\/p>\n
            \n
          1. Add a member variable to the class implementing the XML Web service with a type of SoapUnknownHeader<\/strong> or SoapHeader<\/strong>, or an array of either, to handle multiple unknown SOAP headers.Declaring the type as either an array or a single instance of SoapUnknownHeader<\/strong> has the added benefit that SoapUnknownHeader<\/strong> has an Element<\/strong> property. The Element<\/strong> property is of type XmlElement<\/strong> and represents the XML document for the Header<\/strong> element of the SOAP request or SOAP response. Thus, an XML Web service method can determine the name of the SOAP header, along with the data passed by the SOAP header, by interrogating the Element<\/strong>property.\n
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            C#<\/a><\/div>\n<\/div>\n
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            public class MyWebService {\r\n    public SoapUnknownHeader[] unknownHeaders;\r\n[Visual\u00a0Basic]\r\nPublic Class MyWebService\r\n    Public unknownHeaders() As SoapUnknownHeader<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
          2. Apply a SoapHeader <\/strong>attribute to each XML Web service method that intends to process each unknown SOAP header.\n
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            C#<\/a><\/div>\n<\/div>\n
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                [WebMethod]\r\n    [SoapHeader(\"unknownHeaders\")]\r\n    public string MyWebMethod()\r\n[Visual\u00a0Basic]\r\n    <WebMethod, _\r\n     SoapHeader(\"unknownHeaders\") > _\r\n    Public Function MyWebMethod() As String<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
          3. Add code to determine whether you can process any unknown SOAP headers.If the member variable is of type SoapUnknownHeader<\/strong>, an XML Web service method can determine the name of the SOAP header, along with the data passed by the SOAP header, by interrogating the Element<\/strong> property. The Name<\/strong> property of Element<\/strong>property identifies the name of the SOAP header.\n
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            C#<\/a><\/div>\n<\/div>\n
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            <\/div>\n
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                   foreach (SoapUnknownHeader header in unknownHeaders)\r\n       {\r\n         \/\/ Check to see if this a known header.\r\n         if (header.Element.Name == \"MyKnownHeader\")\r\n[Visual\u00a0Basic]\r\n       Dim header As SoapUnknownHeader\r\n       For Each header In unknownHeaders\r\n         ' Check to see if this is a known header.\r\n         If (header.Element.Name = \"MyKnownHeader\") Then<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/li>\n
          4. Set the DidUnderstand<\/strong> property of the member variable representing the unknown SOAP header to true<\/strong>if it is known how to process a particular SOAP header.If an XML Web service method does process an unknown SOAP header and does not set the DidUnderstand<\/strong> property to true<\/strong>, a SoapHeaderException<\/strong> can be thrown. For more details, see Handling SOAP Headers Required by an XML Web Service Client<\/a>\n
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            C#<\/a><\/div>\n<\/div>\n
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            <\/div>\n
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                     \/\/ Check to see if this is a known header.\r\n         if (header.Element.Name == \"MyKnownHeader\")\r\n               header.DidUnderstand = true;\r\n         else\r\n             \/\/ For those headers that cannot be\r\n             \/\/ processed, set DidUnderstand to false.\r\n             header.DidUnderstand = false;\r\n         }\r\n[Visual\u00a0Basic]\r\n         ' Check to see if this a known header.\r\n         If (header.Element.Name = \"MyKnownHeader\") Then\r\n               header.DidUnderstand = True\r\n         Else\r\n             ' For those headers that cannot be\r\n             ' processed, set DidUnderstand to false.\r\n             header.DidUnderstand = False\r\n         End If<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
            Note<\/strong>\u00a0\u00a0\u00a0The DidUnderstand<\/strong> property is used by XML Web services created using ASP.NET to communicate with the XML Web service method. It is not part of the SOAP specification. Its value does not appear in any part of the SOAP request or SOAP response.<\/p><\/blockquote>\n
            Note<\/strong>\u00a0\u00a0\u00a0When an XML Web service client builds a proxy class using the Web Services Description Language Tool (Wsdl.exe) and an XML Web service defines the member variable representing a SOAP header using the SoapUnknownHeader<\/strong> type, no reference to that SOAP header is added to the proxy class. If an XML Web service client decides to add that SOAP header to the SOAP request, they must modify the proxy class by adding a member variable and applying a SoapHeader<\/strong> attribute to the method making the call to the pertinent XML Web service method.<\/p><\/blockquote>\n<\/li>\n<\/ol>\n
            <\/a>Handling SOAP Headers Required by an XML Web Service Client<\/h3>\n
            A client can require an XML Web service method to interpret the semantics of the SOAP header correctly and process it accordingly for the SOAP request to succeed. To do so, clients set the mustUnderstand<\/strong> attribute of the SOAP header to 1<\/strong>. For instance, the following SOAP request requires the SOAP request recipient to process the MyCustomSoapHeader<\/code> SOAP header.<\/p>\n
            \n
            <\/div>\n
            \n
            <\/div>\n
            \n
            \n
            <?xml version=\"1.0\" encoding=\"utf-8\"?>\r\n<soap:Envelope xmlns:soap=\"http:\/\/schemas.xmlsoap.org\/soap\/envelope\/\" >\r\n  <soap:Header>\r\n    <MyCustomSoapHeader soap:mustUnderstand=\"1\" xmlns=\"http:\/\/www.contoso.com\">\r\n      <custom>Keith<\/custom>\r\n    <\/MyCustomSoapHeader>\r\n  <\/soap:Header>\r\n  <soap:Body>\r\n    <MyUnknownHeaders xmlns=\"http:\/\/www.contoso.com\" \/>\r\n  <\/soap:Body>\r\n<\/soap:Envelope><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
            Whether the XML Web service defines the SOAP header or not determines how the XML Web service should handle SOAP headers required by the client. ASP.NET handles a lot of the work in the case where the XML Web service defines the SOAP header. In the procedure that follows, you can learn how to handle the two cases.<\/p>\n
            To handle SOAP headers not defined by the XML Web service, but required by an XML Web service client<\/strong><\/p>\n