An Overview of the Microsoft 'NET Framework

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An Overviewof theMicrosoft .NETFramework
(c) Allan C. Milne School of Computing Creative
Technologies University of Abertay Dundee
Last updated 26th July 2006
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Agenda

• What is .NET?
• Architecture overview
• Components of .NET
• Some concepts

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So what is .NET ?

• A software development platform
• An execution model framework
• An operating infrastructure
• A framework for distributed systems using
  ubiquitous XML web services
• The biggest change in a Microsoft platform since
  NT replaced DOS

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Some Changes with .NET

• Instruction code formats
• Compilers
• Code loading and execution models
• Type security systems
• Object model
• Class libraries
• Languages
• Metadata

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The .NET Framework is

• A single programming architecture
• Fundamentally object-oriented
• A standard base class library
• Language independent
• Simple to deploy
• Internet enabled
• A single development environment

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The .NET Framework

• web forms
• web services
• mobile devices

ASP.NET Windows forms
ADO.NET and XML
Data access
Base class library
Common to all languages
Common Language Runtime (CLR)
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Common Language Runtime (CLR)

• Manages supports the
• execution of code in the common Intermediate
  Language (IL)
• assembly concept
• IL code with access security type checking
• JIT compiler from IL to native code
• object management
• memory management garbage collection
• unified type system

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.NET Framework Components
Visual Basic
C
C
JScript
more
Common Intermediate Language (IL)
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Managed Code

• Execution of IL code is managed at run-time by
  the CLR
• Memory allocation de-allocation
• Code access security
• Type checking
• JIT compilation to native code
• Thus the CLR exposes a virtual machine to the
  programmer

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Unified Type System

• Type system applies to IL and therefore to all
  source languages
• All types are objects (implicit boxing)
• No variant types
• Unicode characters 1 String type
• Type safe
• CLR verification of IL
• no unsafe casting
• array bounds checking

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Assemblies

• Self-contained, self-describing unit of execution
  deployment
• Executables (.exe) or libraries (.dll)
• Private assemblies can be anywhere
• Shared assemblies are installed in the Global
  Assembly Cache (GAC)
• Contains IL code, metadata resources
• Metadata is contained in the manifest

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Assembly Manifest

• Facilitates code execution, class reflection
  assembly interaction
• Identity versioning
• References file lists
• Expected types
• Fields, methods, properties events of types
• Expected resources
• Security permissions

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Namespaces

• Are a replacement for COM GUIDs
• Organize components into logical groups
  identified by namespace name
• Can be nested to reflect a logical hierarchy of
  functionality, e.g.
• System.Windows.Forms
• One namespace can span several files
• One file can contain several namespaces

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Binding Namespaces

• No special requirements for private assemblies
• add a reference to the .dll file
• then just use the namespace names
• For shared assemblies in the GAC a strong name is
  required
• create with the Shared Name utility
• binds to a 128-bit hash key

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The Class Library

• A large rich library of useful classes
  organised into namespaces
• Enables richer, more rapid, robust productive
  development
• System
• XML
• Collections
• Windows
• Forms

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Using a Class Library
Old Windows API
HWND hwnd hwnd CreateWindowEx
(WS_EX_OVERLAPPEDWINDOW, szAppName,
szAppName, WS_OVERLAPPEDWINDOW, CW_USEDEFAULT,
CW_USEDEFAULT, modewidth, modeheight, NULL,
NULL, hThisInstance, NULL) ShowWindow
(hwnd, nCmdShow) UpdateWindow (hwnd)
.NET Framework (C)
Form form new Form() form.Text My
Window form.Show()
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Deployment

• Assemblies are the units of deployment,
  versioning security
• Can be as simple as copying files - no Windows
  registry needed
• Shared assemblies are added to the Global
  Assembly Cache (GAC)
• Versioning allows deployment use of different
  versions of a component