Web service is the way to publish application's function on web that can be accessible to the rest of the world.
Web services are the components that can be used by other applications
ASP.NET offers easy way to develop web services, just precede the functions with a special WebMethod ()> attribute in order them to work as Web Service.
Web services are discovered using UDDI directory services.
Web services are built on XML standard and use SOAP protocol that allows them to communicate across different platforms and programming languages.
Web services easily manage to work across corporate firewalls as they use HTTP protocol which is firewall friendly.
Web services platform elements are
SOAP (Simple Object Access Protocol)
UDDI (Universal Description, Discovery and Integration)
WSDL (Web Services Description Language)
The web services are built on internet standards that are not platform or language specific.
The .Net framework provides in-built classes to build and consume web services.
The components offered by web services are reusable.
The examples of web service components can be shipment tracking, translation utility, weather forecasting, sports scores etc.
How can you ensure that only authorized users access your Web service?
You should use the element to ensure that only authorized users access your Web service. This element allows or denies access to your Web service according to their role.
Write the names of public properties defined in the WebService class.
There are many properties defined in the WebServices class:
Application - Obtains the application object for the current HTTP request
Context - Obtains the HttpContext object for the current request, which encapsulates all HTTP-specific context used by the HTTP server to process Web requests
Server - Obtains the HttpServerUtility object for the current request
Session - Obtains the HttpSessionState object for the current request
SoapVersion - Obtains the version of the SOAP protocol used to make the SOAP request to a Web service
User - Obtains the Server User Object. This property can be used to authenticate whether a user is authorized to execute the request.
What are the data types supported by Web Services?
.Net web services are built on XML-based standards for exchanging data. This means .NET web services can support only those data types that can be recognized by the XML schema standard. There are many proprietary .Net objects such as FileSteam, Eventlog etc. are not supported in the web services. These data types are .Net specific types that are not universally recognized, i.e. .Net specific only.
You can even exchange custom objects using .Net web services. The only limitation is that only public data members are transmitted, and all public members and properties must use one of the other supported data types.
You can use DataSet and DataTable to return information from database but can't use other ADO.NET objects such as DataColumns and DataRows.
.Net offers a distributed technology called .Net remoting that can plays around wide range of .Net specific data type. But unfortunately, .Net remoting doesn't support client other than .Net.
Describe the EventLog class.
The EventLog class is used to access the Windows event logs from Windows services. Using EventLog, you can also customize Windows event logs that record information about important software and hardware events, such as the events of the .NET controls, keyboard, or other hardware devices.
The EventLog class allows you to read or write to event logs, delete logs, and create as well as delete event sources. You can use the EventLog class to create event logs while creating an event source. An event source can be used to write to only one event log at a particular time. However, it is possible to associate one event log to multiple sources.