Microsoft .NET

ICS243F Presentation

by

Santosh Tawde

What is .NET?

• Microsoft® .NET is a set of Microsoft software technologies for connecting information, people, systems, and devices

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• It is a device and platform independent distributed computing model based on Web Services (which are in turn based on open XML communication technology), and consists of
• a software platform for building .NET experiences
• a programming model and tools to build and integrate XML Web services
• a set of programmable XML Web services
• a way to enable users to interact with a broad range of smart devices via the Web, while ensuring that the user, rather than the application, controls the interaction
• a way to provide a user with applications, services, and devices that are personalized, simple, consistent, and secure

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• .NET is all about creation, consumption and delivery of Web Services

What is a Web Service?

Small, reusable applications written in XML

• Client to Client
• Clients can use XML Web Services to communicate data
• Client to Server
• Clients can send data to and receive data from servers.
• Server to Server
• Servers can share data with each other.
• Service to Service
• web services can work together.

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What are the Components of .NET?

.NET Experience

• .NET Experiences are XML web services that allow you to access information across the internet in an integrated way
• Products transitioning into the .NET experiences are:
• MSN Website
• Visual Studio .NET Website
• Passport Website

.NET Clients

• Clients are PCs, handheld computers, Tablet PCs, game consoles (Xbox), smart phones …

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• All of them use XML Web Services

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• .NET client software includes
• Windows CE
• Windows XP
• Windows Embedded
• Windows 2000

.NET Services

• XML Web Services

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• Offer a direct means for applications to interact with other applications

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• First set of XML Web Services developed are called .NET My Services (“HailStorm”)

.NET Servers

• .NET Enterprise servers are Microsoft's comprehensive family of server applications for building, deploying, and managing scalable, integrated, Web Services and applications

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• Designed with machine critical performance

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• Examples of .NET Servers:
• MS Commerce Server 2000
• MS Exchange Server 2000

.NET Tools

• Microsoft Visual Studio .NET and Microsoft .NET Framework supplies complete solution for developers to build, deploy and run XML services

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• Visual Studio .NET is the next generation of Microsoft’s popular multi-language development tool built especially for .NET

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• Enhances existing languages like Visual Basic with new OO features

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• Introduces C#

Web Services Revisited

• Web services are platform independent
• Encompasses Windows, Unix, Mac, Linux, even PalmOS
• Web services are agnostic of the object model being used
• Compatible with RPC, DCOM, CORBA, and Sun RMI
• Web services are loosely coupled
• Unlike tightly-coupled RPC and distributed object systems, which require all the pieces of an application be deployed at once, you can add clients and servers to Web-based systems as needed
• Web services are built on open standards
• XML, SOAP, WSDL, UDDI, HTTP, RPC
• Web services are compatible with existing object models
• Replaces internal "plumbing" of the network RPC wire format transparently to user
• Web services permit secure transmission
• HTTPS, SSL

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Web Services vs. Traditional Web Applications

• Web services use SOAP messages instead of MIME messages
• Browsers just need to render web pages; web services need to do more
• Web services are not HTTP-specific
• SOAP messages can be sent using SMTP, raw TCP or an instant messaging protocol like Jabber
• Web services provide metadata describing the messages they produce and consume.
• XML Schema (XSD) is used to describe various message structures

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Extensible Markup Language (XML)

• XML is the glue that holds .NET together
• XML is the defacto standard for data interoperability.
• XML provides a way to put structured data into a form that can be easily and quickly transmitted and then interpreted at the other end
• XML looks like HTML, and like HTML, it is readable and text-based
• XML is license-free, platform-independent, and well supported

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Simple Object Access Protocol (SOAP)

“SOAP provides a simple and lightweight mechanism for exchanging structured and typed information between peers in a decentralized, distributed environment using XML “

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A SOAP message is based on XML and contains the following parts:

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• The Envelope is the top-level container representing the message.

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• The Header is a generic container for added features to a SOAP message. SOAP defines attributes to indicate who should deal with a feature and whether understanding is optional or mandatory.

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• The Body is a container for mandatory information intended for the ultimate message receiver.

SOAP (cont’d)

• Soap is the communications protocol for XML Web services.
• SOAP is a specification that defines the XML format for messages—and that's about it – a SOAP implementation will probably include mechanisms for object activation and naming services but the SOAP standard doesn't specify them
• Optional parts of SOAP specification describe how to represent program data as XML and how to use SOAP to do Remote Procedure Calls
• SOAP is much smaller and simpler to implement than many of the previous protocols.
• DCE and CORBA took years to implement, so only a few implementations were ever released; SOAP, however, can use existing XML Parsers and HTTP libraries to do most of the hard work, so a SOAP implementation can be completed in a matter of months – so several implementations for it have been released (> 70 to date).
• SOAP obviously doesn't do everything that DCE or CORBA do, but the lack of complexity in exchange for features is what makes SOAP so readily available

Web Service Description Language (WSDL)

• A Web Service Description defines all the supported methods that a Web Service provides.
• WSDL is an XML grammar that developers and development tools use to represent the capabilities and syntax of a Web Service.
• Similar to IDL for COM and CORBA
• Imagine you want to start calling a SOAP method provided by one of your business partners. WSDL specifies what a request message must contain and what the response message will look like in unambiguous notation.

Universal Discovery Description and Integration (UDDI)

• UDDI is the yellow pages of Web Services
• you can search for a company that offers the services you need, read about the service offered and contact someone for more information
• A UDDI directory entry is an XML file that describes a business and the services it offers.
• There are three parts to an entry in the UDDI directory
• "white pages" describe the company offering the service: name, address, contacts, etc.
• "yellow pages" include industrial categories based on standard taxonomies such as the North American Industry Classification System and the Standard Industrial Classification.
• "green pages" describe the interface to the service in enough detail for someone to write an application to use the Web service.
• UDDI defines a document format and protocol for searching and retrieving discovery documents - which in turn link to DISCO documents.
• DISCO (Discovery of Web Services) is a Microsoft protocol for retrieving the contracts for Web Services (WDSL documents).

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Web Services: An Example

.NET Architecture

Architecture Explained

• Web Services
• Top layer provides .NET users with Web Services for e-commerce and business to business applications
• Frameworks and Libraries
• ASP.NET for developing smart web pages
• ADO.NET which is an XML based improvement for databases and object relational processing
• Interchange Standards
• Platform independent means of exchanging objects
• SOAP (Simple Object Access Protocol)
• WSDL (Web Services Description Language)

Architecture Explained (cont’d)

• Development Environment
• Visual Studio .NET
• Visual C++, Visual BASIC, Visual C#
• Component Model
• Derived from original component based development: CORBA, J2EE, COM
• .NET allows building “assemblies” consisting of a number of classes with well defined interface
• IDL absent in .NET

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Architecture Explained (cont’d)

• Object Model
• Conceptual basis for everything in .NET
• Common Language Runtime
• Basic set of mechanisms for executing .NET programs regardless of language of origin

.NET Framework

Windows Forms

ASP.NET

Web Services

ASP.NET Application Services

Web Forms

Controls

Drawing

Windows Application Services

Framework Class Library

ADO.NET

Network

XML

Security

Threading

Diagnostics

IO

Etc.

Common Language Runtime

Memory Management

Common Type System

Lifecycle Monitoring

Framework Class Library

• The FCL is a hierarchical class library that can be utilized across multiple languages and platforms.
• Contains reusable classes, interfaces, and components that can be used for:
• Developing components and Web Services.
• Developing Windows Forms applications.
• Developing Web Forms applications.
• Working with Directory Services, Event Logs, Processes, Message Queues, and Timers.
• Creating and managing threads.
• Managing application security.
• Key features and benefits
• Cross-Language Interoperability
• Consistent and Unified Programming Model
• Object-Oriented and Extensible Class Library

Common Language Runtime

• The CLR is at the core of the .NET platform - the execution engine. A unifying framework for designing, developing, deploying, and executing distributed components and applications.
• Loads and runs code written in any runtime-aware programming language (approx. 22 as of now).
• Manages memory, thread execution, type safety verification and garbage collection.
• Performs compilation (Just In-time Compiler)
• Makes use of a new common type system capable of expressing the semantics of most modern programming languages. The common type system defines a standard set of types and rules for creating new types.
• Inheritance/Reference NOT dependent on source language

MSIL and JIT Compilation

• Source code is compiled into MSIL (Microsoft Intermediate Language). Similar to Java bytecode.
• MSIL allows for runtime type-safety and security, as well as portable execution platforms (all Windows). MSIL code cannot play tricks with pointers or illegal type conversions.
• The MSIL architecture results in apps that run in one address space - thus much less OS overhead.
• Compilers also produce “metadata”:
• Definitions of each type in your code.
• Signatures of each type’s members.
• Members that your code references.
• Other runtime data for the CLR.
• Metadata along with the MSIL enables code to be self-describing - no need for separate type libraries, IDL, or registry entries.
• When code is executed by the CLR, a JIT compilation step occurs. Code is compiled method-by-method to native machine code.

Packaging: Modules, Types, Assemblies, and the Manifest

Assembly

Manifest

Module

Metadata

MSIL

Type

Type

Type

Packaging: Modules, Types, Assemblies, and the Manifest

• A “module” refers to a binary, such as an EXE or DLL.
• Modules contain definitions of types, such as classes, interfaces, structures, and enumerations.
• An assembly contains a “manifest”, which is a catalog of component metadata containing:
• Assembly name.
• Version (major, minor, revision, build).
• Assembly file list - all files “contained” in the assembly.
• Type references - mapping the managed types included in the assembly with the files that contain them.
• Scope - private or shared.
• Referenced assemblies.
• No MSIL code can be executed unless there is a manifest associated with it.

Packaging: Modules, Types, Assemblies, and the Manifest

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• An assembly can be defined as one or more modules that make up a unit of functionality. Assemblies also can “contain” other files that make up an application, such as bitmaps and resource files.
• An assembly is not a physical file.
• An assembly is the fundamental unit of deployment, version control, activation scoping, and security permissions.
• Two types of assemblies:
• Private - Usually deployed in the same directory as the client application and used only by a single application.
• Shared - Used by any application and usually installed in a special Global Assembly Cache.

.NET Component Model

• Offers developers an component model directly based on OO.
• Removes distinction between a program element and a software component. Thus it provides significant benefits over technologies like CORBA and COM.
• .Net gets rid of the IDL - we can use a .Net assembly directly as a component.
• Uses interface documentation already present in the source code. Compliers for .Net supported languages retain this information as metadata - self documented components.
• Metadata is also available in XML format, any application whether it is a part of .NET or not can obtain information about components.

Microsoft C#

• A modern, object-oriented programming language built from the ground up to exploit the power of XML-based Web services on the .NET platform.
• The main design goal of C# was simplicity rather than pure power.
• Features of C#

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Simplicity Type Safety

Consistency Version Control

Modernity Compatibility

Object Orientation Flexibility

.NET security

• The .NET Security Framework Architecture consists of the following five core elements:
• Evidence Based Security - At runtime, the CLR determines permission requests by evaluating the assembly’s evidence.
• Code Access Security - allows code to be trusted to varying degrees, depending on where the code originates and on other aspects of the code's identity.
• Verification - during JIT, the CLR ensures memory type safety.
• Role Based Security - .NET applications can make authorization decisions based on identity and role membership.
• Cryptography - The .NET Framework provides Random Number Generation and other Cryptographic services.

Conclusion

• .Net creates a new concept, “the Internet Operating System”.
• .Net allows cross-platform development to an extent not before possible.
• .Net web services can be integrated into existing distributed object technologies today by replacing their RPC wire protocol with SOAP .
• Large-scale distributed application development and deployment become possible on a level that presents major difficulties today.
• Stricter versioning policies help to ensure greater stability during upgrades, even in shared libraries.
• "Software as a service" - a subscription model for application deployment - becomes a feasible option.