additional .net concepts
DESCRIPTION
Additional .NET Concepts. Daragh Byrne – EPCC. Purpose. Web Services using ASP.NET Basis of MS.NETGrid software Assemblies Metadata and reflection Application configuration. ASP.NET and Web Services. ASP.NET Features. Unified Web Development Platform - PowerPoint PPT PresentationTRANSCRIPT
http://www.epcc.ed.ac.uk/~ogsanet
February 24th-25th 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
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ASP.NET and Web Services
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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
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Request Handling
IIS (aspnet_isapi.dll)
Request
asmx handler aspx handler
Response Response
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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
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ASP.NET Request Handling
HTTP request to foo.aspx
ASP.NET
foo.aspx
Compile and execute Output (html)
HTTP Response to client
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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
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Web Service Request Handling
SOAP request to foo.asmx
ASP.NET
Foo.asmx
Execute Output (SOAP)
SOAP Response to client
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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
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Useful Attributes
WebServiceAttribute– BufferResponse– Description– MessageName
Can use WebServiceAttribute to set properties of the service:
– [WebService( Namespace=“someURI”, Description=“Some text describing the service”)]
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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
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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
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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/
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Assemblies
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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
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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
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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
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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
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Using Metadata
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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() { }}
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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(){ }
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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{}
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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
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Application Configuration
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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
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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>
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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