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The Common Language Runtime (CLR)

Based on

Mark Sapossnek

Computer Science DepartmentMetropolitan College

Boston University

Agenda

What Is the CLR?AssembliesExecution Model

Web Form

.NET Framework

Windows

Web Service

CLR

What is the CLR?The .NET Platform

.NET FoundationWeb Services

Your InternalWeb Service

Third-PartyWeb Services

.NET EnterpriseServers

Clients Applications

Protocols: HTTP,HTML, XML, SOAP, UDDI

Tools:Visual Studio.NET,

Notepad

A set of technologies for developing and using components to create:

Web FormsWeb ServicesWindows applications

Supports the software lifecycleDevelopmentDebuggingDeployment Maintenance

What Is the CLR?The .NET Framework

Common Language Specification

Common Language Runtime

VB C++ C#

ASP.NET: Web Servicesand Web Forms

JScript …

WindowsForms

Base Classes

ADO.NET: Data and XML

Visual Studio.NET

What Is the CLR?The .NET Framework

What Is the CLR?Overview

The CLR provides a run-time environment that manages the execution of code and provides services that improves development, deploy-ment, and run time.Code that targets the CLR is called managed code.

What Is the CLR?Goals

Development servicesDeep cross-language interoperabilityIncreased productivity

Deployment servicesSimple, reliable deploymentFewer versioning problems – NO MORE ‘DLL HELL’

Run-time servicesPerformance Scalability Availability

What Is the CLR?Goal: Simpler Development

Plumbing disappearsMetadataTransparent proxiesMemory managementConsistent exception handling

Great WYSIWYG tool supportDesigners and wizardsDebuggers Profilers

Increased productivity

What Is the CLR?Goal: Simpler, Safer Deployment

No registration, zero-impact installXCOPY deployment, incremental download

Side-by-side versions of shared componentsCapture version at compile timeAdministrative policy at run time

Evidence-based security policyBased on code as well as userCode origin (location)Publisher (public key)

DLL Hell

What Is the CLR?Goal: Scalability

Smart device to Web FarmAutomatic memory management

Self-configuringDynamically tuning

Thread poolAsynchronous messaging

Object remotingEvents

Smart device versionMultiple RTOSesSame tools used for desktop

What Is the CLR?Goal: Rich Web Clients, Safe Hosting

WinForms on the clientASP.NET Web Forms on the serverCode is granted permissions

Evidence is used by policy to grant permissionsApplication that starts runtime

Like Internet Explorer, IIS, SQL Server™, Shell

Provides some evidenceControls code loadingMaps applications to processes

COM, ASP, VB, C++All services availableMany services redesigned

Ease of useScalabilityConsistent API

Consistent framework raises the abstraction layerGradual transition from simplicity to full powerLess training, greater productivity

What Is the CLR?Goal: Converge Programming Models

What Is the CLR?Goal: Multiple Languages

Common Type SystemObject-oriented in flavorProcedural languages well supportedFunctional languages possible

CLS guides frameworks designRules for wide reachAll .NET Framework functionality available

Over 15 languages investigatedMost are CLS consumersMany are CLS extenders

Choose the right language for a particular job

What Is the CLR?Highlights

Common Type SystemMapping of data types: Programming language Framework

Just-in-time (JIT) compilersJIT compiles intermediate language (MSIL) into native codeHighly optimized for platform or device

Garbage collectorPermission and policy-based securityExceptionsThreadingReflectionDiagnostics and profiling

What Is the CLR?Services

Code managementMemory management and isolationVerification of type safetyConversion of MSIL to native code Loading and execution of managed code Creation and management of metadataInsertion and execution of security checks

Handling cross-language exceptionsInteroperation between .NET Framework objects and COM objects and Win32 DLLsAutomation of object layout for late bindingDeveloper services (profiling, debugging, etc.)

What Is the CLR? Architecture

Class Loader

MSIL to NativeCompilers (JIT)

CodeManager

GarbageCollector (GC)

Security Engine Debug Engine

Type Checker Exception Manager

Thread Support COM Marshaler

Base Class Library (.NET Framework) Support

What Is the CLR? Soon To Be a Standard

Microsoft, with HP and Intel, submitted proposal to ECMA to standardize:

C#Common Language Infrastructure

Includes the Common Language Runtime and a subset of the .NET Framework classes

http://msdn.microsoft.com/net/ecma/http://www.ecma.ch

Agenda

What Is the CLR? AssembliesExecution ModelInteroperabilitySecurity

AssembliesOverview

Contains code and metadataAssemblies function as:

Unit of deploymentType boundarySecurity boundaryReference scope boundaryVersion boundaryUnit of side-by-side execution

AssembliesOverview

Assemblies can be:Static: DLL, EXE

Uses existing COFF binary formatVia existing extension mechanism

DynamicCreate assemblies with

.NET Framework SDKVisual Studio.NETYour own code

Dynamic assemblies

ManifestMetadata about the assembly itself

Type metadata Completely describes all types defined in an assembly

Managed codeMicrosoft Intermediate Language (MSIL)

ResourcesFor example, .bmp, .jpg

AssembliesComponents of an Assembly

Manifest

MSIL

Resources

ParcelTracker.DLL


Type Metadata


An assembly is a logical unit, not physicalIt can consist of multiple modules (.DLL, .JPG, etc.)

AssemblyModule

FileType

In this figure, containment implies a 1:M relationship


A single-file assembly A multi-file assembly

ManifestMetadata

MSIL

File1.dll Metadata

MSIL

File2.dll Graphic.jpg

Resource

Logo.gif

Resource

Manifest

File3.dll

AssembliesAssembly Generation Tool: al.exe

Takes one or more files (containing either MSIL or resource files) and produces a file with an assembly manifest.When compiling a C# file, you can specify that it create a module instead of an assembly by using /target:module.

AssembliesManifest

Manifest contains:Identity information

Name, version number, culture, strong name

List of files in the assemblyMap of assembly types to filesDependencies

Other assemblies used by this assembly

Exported typesSecurity permissions needed to run

Type Descriptions

ClassesBase classesImplemented interfacesData membersMethods

Assembly Description

NameVersionCulture

Other assembliesSecurity PermissionsExported Types

AssembliesManifest and Metadata

Manifest

Metadata

AssembliesWhat’s In the Metadata

Description of typesName, visibility, base class, interfaces implementedMembers

methods, fields, properties, events, nested types

AttributesUser-definedCompiler-definedFramework-defined

AssembliesDemo: ILDASM.EXE

Allows you to inspect the metadata and disassembled IL code in an assemblyGreat way to see what’s really going onUse ildasm /? to see the various options

AssembliesMetadata

Key to simpler programming modelGenerated automatically

Stored with code in executable file (.dll or .exe)

AssembliesMetadata: Creation and Use

Assembly(Manifest, metadataand code)

Debugger

Schema Generator

Profiler

OtherCompiler

Proxy Generator

Type Browser

Compiler

SourceCode

XML encoding(WSDL)

Serialization(e.g. SOAP)

Designers

Reflection

AssembliesCompilers Use Metadata

For cross-language data type importEmit metadata with output code

Describe types defined and usedRecord external assemblies referencedRecord version information

Custom attributes can be used ObsoleteCLS complianceCompiled for debuggingLanguage-specific markers

AssembliesOther Tools Use Metadata

Designer behavior Controlled by user-supplied attributes

CategoryDescription

Designer extensibilityUser-supplied attributes specify code to use

Type convertersEditors

Web methods marked by custom attributeType viewer

AssembliesGlobal Assembly Cache

A set of assemblies that can be referenced by any application on a machineShould be used only when needed

Private assemblies are preferredLocated at %SystemRoot%\assembly

(c:\winnt\assembly)Add assemblies by

Installer programgacutil.exeWindows Explorer

Assembly Cache Viewer (shfusion.dll) is a shell extension for GAC that is installed with the .NET Framework SDK

.NET Framework Configuration Tool (mscorcfg.msc)Assembly must have a strong name

AssembliesStrong Names

Strong names identify an assemblyContains text name, version, culture, public key, and digital signature

Generated from an assembly using a private keyBenefits

Guarantees name uniquenessProtect version lineage

No one else can create a new version of your assemblyProvides strong integrity check

Guarantees that contents of an assembly didn’t change since it was built

AssembliesStrong Names

To sign an assembly with a strong name:Use Assembly Generation tool: al.exeUse assembly attributes (AssemblyKeyFileAttribute or AssemblyKeyNameAttribute)

Requires a key pair (private and public) To generate a key pair use the Strong Name tool: sn.exe

AssembliesDemo: Installing an Assembly in GAC

Create assemblySign assembly with key from sn.exeInstall into GAC via gacutil.exe, Assembly Cache Viewer and .NET Framework Configuration Tool

AssembliesSigncode

A strong name identifies an assembly but it does not authenticate an assembly

Strong names do NOT imply a level of trustSigncode allows the embedding of a certificate in an assembly

Now your assembly can be authenticated

AssembliesSigncode

To use signcode:Obtain a Software Publisher Certificate (.spc)Use signcode.exe to sign the assembly

Signcode can only sign one file at a timeFor an assembly, you sign the file containing the manifest

Purchase one from a well known Certificate Authority (such as Verisign)Create your own

For testing purposes onlyUse Makecert.exe to create a X.509 certificateUse cert2spc.exe to generate an SPC from a X.509 certificate

AssembliesHow Do You Obtain a Certificate?

AssembliesStrong Names and Signcode

Strong names and signcode provide different, complimentary levels of protectionYou can assign a strong name or assign a signcode signature to an assembly, or both When using both, the strong name must be assigned first

AssembliesSigncode

Specify what permissions your assembly needsOnly specify required permissionsHandle optional permissions dynamically

Set security policy on run-time machine

Unit of deploymentOne or more files, independent of packagingSelf-describing via manifest and metadata

VersioningCaptured by compilerPolicy per-application as well as per-machine

Security boundaryAssemblies are granted permissionsMethods can demand proof that a permission has been granted to entire call chain

Mediate type import and exportTypes named relative to assembly

AssembliesDeployment

AssembliesDeployment

Applications are configurable unitsOne or more assembliesApplication-specific files or data

Assemblies are located based on:Their logical name and the application that loads them

Applications can have private versions of assemblies

Private version preferred to shared versionVersion policy can be per application

AssembliesMSIL

Microsoft Intermediate Language

.assembly hello {}

.assembly extern mscorlib {}

.method static public void main() il managed {.entrypoint.maxstack 1ldstr "Hello World from IL!"call void [mscorlib]System.Console::WriteLine(class

System.String)ret

}

AssembliesMSIL

Compiled with ilasm.exeMSIL was designed for the CLR

Object-oriented (primitives are not special)Designed for the Common Type SystemDoes not embed type information

See documentation in \FrameworkSDK\Tool Developers Guide\docs

Agenda

What Is the CLR? AssembliesExecution ModelInteroperabilitySecurity

Source Code

C++, C#, VB or any .NET language

csc.exe or vbc.exeCompiler

Assembly

DLL or EXE

Execution ModelCreate Assembly

CLR

Execution Model

VBSource Code

CompilerC++C#

Assembly AssemblyAssembly

Operating System Services

MSIL

Common Language Runtime JIT Compiler

Compiler Compiler

NativeCode

ManagedCode

ManagedCode

ManagedCode

UnmanagedCode

CLR Services

Ngen

Execution ModelCompiling IL to Native Code

JIT compilerGenerates optimized native codeCompiled when a method is first calledIncludes verification of IL code

Ngen.exe

Install-time native code generationUsed when assembly is installed on machineReduces start-up timeNative code has version checks and reverts to run-time JIT if they fail

Execution ModelRun-Time Hosts

ASP.NETInternet ExplorerShell executablesMore in future

For example: SQL Server (Yukon)Can create your own run-time hosts

Execution ModelBinding to Assemblies

An application consists of one or more assemblies.How does one assembly bind to another?

Based upon metadata and policyLocal (preferred)Assembly Global Cache

Multiple versions of an assembly may exist on the same machine.

Easier software deployment, updates and removalMultiple versions of an assembly can even be used by the same application

Execution ModelApplication Domains

Traditionally, processes were used to isolate applications running on the same computer

Isolates failure of one applicationIsolates memory

ProblemsUses more resourcesIf needed, inter-process calls can be expensive


.NET introduces Application Domains, which allow you to run multiple applications within the same processEnabled by code verification

No code will crash the processManaged by the System.AppDomain classCommon assemblies can be shared across domains or can be specific to a domain


Benefits:Application domains are isolatedFaults are isolatedIndividual applications can be stopped without stopping the processCan configure each application domain independentlyCan configure security for each domainCross-domain calls can be done through proxies

More efficient than cross-process calls


ProcessShared class dataand native code

App.Domain

(class dataand

native code)

App.Domain

Thread

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