Additional .NET Concepts

1. Additional .NET Concepts Daragh Byrne – EPCC

2. Purpose • Web Services using ASP.NET • Basis of MS.NETGrid software • Assemblies • Metadata and reflection • Application configuration

3. ASP.NET and Web Services

4. ASP.NET Features • Unified Web Development Platform • Runs under Microsoft Internet Information Services (IIS): • Available on all Windows Platforms better than Win2K • Requires .NET runtime (CLR) • Combines traditional forms-based Web Application development and Web Services • Runs compiled applications so performs better than traditional ASP • Excellent support in Visual Studio .NET • WYSIWYG-based design like designing Windows Forms

5. Reference • Material from this lecture covered in great detail in your “Building Web Services” book: • Chapter 6 in particular

6. Web Applications in ASP.NET • The files present in a virtual directory under IIS comprise a Web Application: • Isolated application domain for each Web application • Can contain both Web pages and Web Services • Lives in own AppDomain: • Memory protected region within a process, a .NET feature • Protects applications from one another • Requests for a page/service are mapped by IIS to the ASP.NET handler: • aspnet_isapi.dll, aspnet_wp.exe • Listen for file extensions .aspx, .asmx etc • Work carried out by a recycled process for efficiency and stability • Configuration is handled by Web.config in the root directory: • Web.config is standard ASP.NET application configuration file

7. Request Handling Request IIS (aspnet_isapi.dll) Response Response asmx handler aspx handler

8. Web Pages in ASP.NET • HTML lives in .aspx files: • Code can be placed here, or • Code in separate file • Presentation layer separated from logic: • A step away from the ugly embedded ASP model • Supports Web controls: • Reusable UI elements, e.g. menus, date-pickers • Can write custom controls • More details available in .NET framework documentation: • We concentrate on the Web Services aspect

9. ASP.NET Request Handling foo.aspx HTTP request to foo.aspx HTTP Response to client ASP.NET Output (html) Compile and execute

10. Web Services in ASP.NET • Write a class that provides the service functionality: • Tag operations with WebMethod attribute • Tag class with WebService attribute to specify default namespace of the service • Write a .asmx file: • References the implementing class • Can separate .asmx file and source code

11. Web Service Request Handling Foo.asmx SOAP request to foo.asmx SOAP Response to client ASP.NET Output (SOAP) Execute

12. Example Web Service // HelloService.asmx <% WebService Class=“HelloService” %> .. .. .. // HelloService.cs [WebService( NameSpace=“http://myURL.com/HelloService” )] public class HelloService {[WebMethod]public string SayHello(string name){ return “Hello there, “ + name);} } • Compile and deploy under ASP.NET: • Easiest with Visual Studio .NET • Build a client

13. Useful Attributes • WebServiceAttribute • BufferResponse • Description • MessageName • Can use WebServiceAttributeto set properties of the service: • [WebService( Namespace=“someURI”, Description=“Some text describing the service”)]

14. Automatic WSDL Generation • ASP.NET will automatically generate WSDL service descriptions • Send WSDL on the query string to see this: • e.g. service at http://localhost/myservice.asmx?WSDL • Reflection on service type to generate this document: • Uses e.g. WebMethod attributes to generate operation elements • Can control contents of WSDL document with attributes: • e.g. SoapDocumentMethodAttribute • Can suppress WSDL generation and do custom generation

15. Building Web Service Clients • Idea is that accessing a Web Service is as simple as making method call • Use the WSDL description to auto-generate client ‘proxy’ classes • .NET Framework provides wsdl.exe tool: • wsdl http://myhost.com/SomeService.asmx?wsdl /o:ServiceProxy.dll • Examines a WSDL document • Outputs a DLL with a class that represents the service: • Derived from SoapHttpClientProtocol class, which handles serialization, invocation, etc • Highly integrated with Visual Studio.NET: • Does wsdl.exe behind the scenes, adds proxy stub to project automatically

16. Web Services Enhancements • SDK to support emerging W3C Web Services protocols that address: • Security (WS-Security) • Policy • Routing • Custom SOAP Attachments • Reliable messaging • Now at version 2.0: • http://msdn.microsoft.com/webservices/building/wse/

17. Assemblies

18. Assemblies • Assemblies are the unit of code distribution in .NET • May be independently versioned • May be digitally signed • Scope the types within them • Are the basis of Code Access Security: • Code from an assembly can do certain things based on level of trust of assembly provider

19. Working with Assemblies • Logical assembly consists of a number of modules (files): • Primary module references the other modules • Primary module identifies assembly • Most cases only one module • Assemblies contain code, data and/or resources: • e.g icon byte streams. • Assemblies scope the types and data within them: • public, private, internal(package level in Java) modifiers apply to types at assembly level • Same type defined in different assemblies == different types • Assembly names are resolved by the runtime before loading: • Must reside in APPBASE or subdirectory: • APPBASE is standard location off application directory, usually /bin • APPBASE can be changed using configuration files

20. Assembly Identification • Assemblies may be strongly-named or weakly-named: • Weakly-named just identified by the name of the primary module, minus the .dll or .exe • Strongly-named have version, culture, public key as well • Concurrent versions of an assembly stored in the Global Assembly Cache: • Can only store strongly-named • Can specify dependence of application on particular assembly in configuration file

21. Dynamic Assembly Loading • Can work with Assemblies programmatically: • Members on the System.Reflection.Assembly class • Assembly.Load • Assembly.LoadFrom • Assembly.CreateInstance(string typeName) • Assembly.GetCustomAttributes() • Important to know about assemblies for our OGSI implementation

22. Using Metadata

23. Attributes • Attributes allow you to add metadata to your types: • Enables a declarative style of programming • Can use framework-supplied or custom attributes • Information from attributes are stored in metadata for that type • Example: public class MyClass{ [System.Obsolete(“Will be removed next release”)] public void SomeObsoleteMethod() { }}

24. Common Attribute Uses • Conditional compilation/calling: [Conditional(“DEBUG”)]public void myDebugMethod(string s) {} • XML serialisation: [XmlElement(“name”, someNameSpace)public string name_; • Web Service operations: [WebMethod]public string MyWebMethod(){ }

25. Custom Attributes • Can define own attribute: • Inherit from System.Attribute • Define usage using – you guessed it – an attribute! • Example: [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]public class SomeUsefulAttribute: System.Attribute{ public SomeUsefulAttribute(string s) { }}// Use like[SomeUseful(“Hello”)]public class SomeClass{}

26. The Reflection API • Can get access to your attributes using this API: public void SomeCode(){ object [] customAttributes = someObject.GetType().GetCustomAttributes( typeof(SomeUsefulAttribute)); foreach(SomeUsefulAttribute attr in customAttributes) { //process } } • Can get attributes on methods, fields, etc in a similar manner: • See the .NET documentation for System.Reflection namespace

27. Application Configuration

28. Application Configuration • Previously ad-hoc, comma-separated value files, language-specific etc: • Lots of different standards • .NET aims to provide consistent configuration for every application: • XML file-based • XML file in same directory as application usually • System.Configuration namespace provides API for doing this: • Extensible to use your own configuration schema • Web applications use the Web.config file as default

29. Example Configuration File <?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <sectionGroup name="gridContainer.config"> <section name="containerProperties“ type=“HandlerType"/> <section name="gridServiceDeployment“ type=“HandlerType"/> </sectionGroup> </configSections> <system.web> <!- - Web Application Configuration - - > </system.web> <system.runtime.remoting /> <gridContainer.config> <containerProperties> ... </containerProperties> <gridServiceDeployment> ... </gridServiceDeployment> </gridContainer.config> </configuration>

30. Other .NET Topics of Interest • Win32/COM interoperation: • Legacy integration • WinForms: • Smart clients, href-exes (executables over HTTP) • Asynchronous execution: • Threads, delegates • Support for event-driven programming in C# • ADO.NET • XML Libraries