Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

effectively exposed over the Web, a Web service method requires a special attribute inaddition to being declared as public. Only methods marked with the WebMethodattribute gain the level of visibility sufficient to make them available over the Web.The WebMethod AttributeIn practice, the WebMethod attribute represents a member modifier similar to public,protected, or internal. Only public methods are affected by WebMethod, and theattribute is effective only to callers invoking the class over the Web. This characteristicincreases the overall flexibility of the class design. A software component allowed toinstantiate the Web service class sees all the public methods and does not necessarilyrecognize the service as a Web service. However, when the same component isinvoked as part of a Web service, the IIS and ASP.NET infrastructure ensure thatexternal callers can see only methods marked with the WebMethod attribute. Anyattempt to invoke untagged methods via a URL results in a failure.The WebMethod attribute features several properties that you can use to adjust thebehavior of the method. Table 13-1 lists the properties.Table 13-1: Properties of the WebMethod AttributePropertyBufferResponseCacheDurationDescriptionEnableSessionMessageNameTransactionOptionDescriptionSet to true by default, this property indicates that theIIS run time should buffer the method's entire responsebefore sending it to the client. Even if set to false, theresponse is partially buffered; however, in this case,the size of the buffer is limited to 16 KB.Specifies the number of seconds that the IIS run timeshould cache the response of the method. Thisinformation is useful when you can foresee that themethod will handle several calls in a short period oftime. Set to 0 by default (meaning no caching), thecaching engine is smart enough to recognize andcache page invocations that use different parametervalues.Provides the description for the method. The value ofthe property is then embedded into the WSDLdescription of the service.Set to false by default, this property makes available tothe method the Session object of the ASP.NETenvironment. Depending on how Session isconfigured, using this property might require cookiesupport on the client or a Microsoft SQL Server 2000installation on the server.Allows you to provide a publicly callable name for themethod. When you set this property, the resultingSOAP messages for the method target the name youset instead of the actual name. Use this property togive distinct names to overloaded methods in theevent that you use the same class as part of themiddle tier and a Web service.Specifies the level of COM+ transactional support youwant for the method. A Web service method can haveonly two behaviors, regardless of the value assigned460