Exam Essentials

Know how to create and consume an XML Web service.  Visual Studio .NET offers you a built-in template that makes setting up XML Web services easy. XML Web service applications inherit from the System.Web.Services namespace. Client applications use a proxy class, generated when a reference is added to the client project, in order to communicate with an XML Web service as though it were a local class. After the Web reference is added, local objects that represent the Web service can be instantiated and method calls on these proxy objects are forwarded to the XML Web service.

Be familiar with the attributes that are available for the System.Web.Services.WebService class.

Know how to use the WebService and WebMethod attributes. Know how to control the way that the XML wire format for the SOAP message is created by using the SoapDocumentMethod and SoapRpcMethod attributes.

Know how to instantiate and invoke an XML Web service. Use Visual Studio .NET to set web references to XML Web services in your client applications. Understand how a proxy class is generated so that you can call XML Web service methods, just as if you were calling methods on a local object.

Know how to create client applications that call Web methods asynchronously. Use the Beginmethodname and Endmethodname procedures that are automatically generated in the proxy class code to initiate and complete asynchronous calls. Use the .NET Framework AsyncCallback class to enable this behavior.

Understand how custom SOAP headers enable you to pass application-specific identifiers as a part of the SOAP message. Know how to add a class to your XML Web service project that has public variables to handle the custom SOAP header fields. Instantiate an instance of this class in your client project to set values for the custom SOAP header fields. Retrieve the custom SOAP header values that are passed to your Web method code.

Understand how to add custom processing while sending and receiving SOAP messages by using SOAP extensions. Know how to add a class to your XML Web services project that inherits from the SoapExtension base class and overrides the base methods for GetInitializer, Initialize, ChainStream, and ProcessMessage.