February 24 th -25 th 2004 Daragh Byrne – EPCC Additional.NET Concepts

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

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

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 SOAP request to foo.asmx ASP.NET Foo.asmx Execute Output (SOAP) SOAP Response to client

12 Example Web Service // HelloService.asmx // HelloService.cs [WebService( NameSpace=“ )] 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 WebServiceAttribute to 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  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 /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: –

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......

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