ASSEMBLIES AND THE GACCHAPTER 1, LESSONS 4-7 & LAB

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.NET ASSEMBLIES

. Net assembly

Fundamental unit for app development and deployment

Contains types and resources that app requires

type

type

resources

Resources

•Strings

•Images (PNG, GIF,JPEG,BMP,TIFF)

•Icons

•Audio

•Files

•Other

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Shared Assemblies

Assembly

Application Application

Global Assembly

Cache (GAC)

(machine-wide)

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Inside an Assembly

MSIL

Code

Type

Metadata

Assembly

Manifest

CLRRuns

code

CLR uses metadata to

run code

Assembly

Metadata

contains

•Version

•Security Identity

•Resources required

•Scope

Must be present before

assembly can run

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Assembly Manifest Version Information

• Defines version of an app– Smallest unit of a version of an app

• Establishes version of types within assembly

• Multiple versions of an assembly can execute– Side by side execution– Avoids “DLL Hell” of COM Applications

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Assemblies - Permissions

• Assembly is smallest unit granted permission by Framework

• Provide security boundaries• You specify permission required when

building assembly• When assembly is loaded:

1. Assembly sends request to runtime to grant permission

2. Runtime checks the security policy files• Files are on system running app• Sys admin configures these files using tools

described in Lesson 7.

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What are the boundaries of a type?

• Assemblies provide boundaries for types

• Type identity = type name + name of assembly in which it resides

Assemby 1

Type “A”

Assemby 2

Type “A”

OK

Assembly

Namespace 1

Type “A”

Namespace 2

Type “A”OK, also

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.Net Framework Class Library Namespaces

• Library is made up of reusable classes• Classes organized into hierarchical

namespaces– Logically and functionally related classes– Divides assembly into logical grouping of types– Ex:

• System– System.Data – DB apps– System.I/O – all I/O operations

• A given namespace may appear in multiple assemblies

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Static and Dynamic Assemblies

.net language

compiler

static assembly

(.exe or .dll)

produces

harddisk

Your App

( at runtime)

Requires a type from an existing assembly

Reflection

APIs

Creates

Portable Execution

file

harddisk

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Single File vs Multiple File Assemblies

SINGLE FILE ASSEMBLY

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Multiple File Assembly

Can be used when different modules are written in different languages.

More efficient downloading: store seldom-used together, download only when necessary

Use Assembly Linker (AL.EXE) to link multiple modules into single assembly (Lesson 7).

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Private vs Shared Assemblies

• Private:– Stored in installation directory of app– Accessible to app only

• Shared:– Accessed by multiple apps– Has strong name

• Assembly name• Version• Culture information• Digital signature• Public key information

– Stored in GAC

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Assembly IdentityEstablished by info in the Assembly ManifestAssembly Manifest

Contents

String

<ver maj>.<ver min>.<revision>.<build>

Culture, Language supported

Public Key info

Identifies files that contain type declaration & implementation

Assembly name, assembly metadata, public key (if SN)

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Establishing Assembly Identity

Apply attributes in AssemblyInfo file

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XCopy Deployment

• Use XCopy to deploy– Make sure all files in assembly are in

same application directory– Framework searches for referenced

assemblies in application folder– Assemblies in one app folder are not

accessible by another app in another directory

• (Above) Private Assemblies

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Shared Assemblies

• Installed in GAC• Assign strong name to assembly (required)

– Assembly indentity, public key, digital signature• SN.EXE – verification, key pair/signature sn –k MyKey.dat key pair in MyKey.DAT

– Use this file name in attribute to assign the assembly a strong name

Imports System.Reflection <Assembly: AssemblyKeyFile("MyKey.dat")>

Use GACUTIL.exe to install in GACgacutil /u <assembly>

GAC in %WINDOWS%\assembly folder

Configuration and Security

Lesson 5

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Configuration and Security Policy Files

Configuration files

Security Policy files

Computer

Application

.NET Framework

uses control behavior

.NET

Tools

Modify

settings

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Application Configuration.NET

Framework

Application Code

controls

What resources can this code

access?

Depends on:

Origin of code

Who is running the code

To control execution

You must configure one or more Configuration files

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Configuration FileConfiguration file is an XML document

It contains predefined elements

element

Note Start and End Tags

shows location of assembly

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Configuration Files

Machine configuration (machine.config)

Application configuration files

Security Configuration Files

Note: configuration file code is case-sensitive!

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Machine.config fileLocated in %runtime installation path%\config

%runtime installation path% is an ENVIRONMENT VARIABLE to set up an environment variable: My Computer | Properties | Advanced | Environment variables enter the name and value under System Variables

Note “appSettings” section (can be modified by you)

When you run an app, framework checks for changes in:

1. Machine.config

2. Application configuration file

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Application Configuration files

(above) Using an app.config file to save connection strings

Could be used to take a server offline without recompiling:

change the value of the element and restart the app

app can use the config file to read the value of the ServerButton.Text key

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Where are app.config files located

Depends on run-time host:

Executable-hosted apps: <appname>.exe.config file created in same directory as executable.

ASP.NET-hosted apps: Named Web.config

Located in web application folder

Given URL: www.microsoft.com/app1/app2

App1 config file in www.microsoft.com/app1

App2 config file in www.microsoft.com/app2

App2 is affected by both config files

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Security Configuration FilesContain security permissions for hierarchies of code groups.

Code groups: logical groups of code

enterprise – permissions granted affect code on all machines in organization

machine – affect code on a particular computer

user levels – affect code when a particular user executes an application

An executing app only gets permissions granted at intersection of enterprise, machine, and user levels

Security config files located at (entprs,mach)%runtime install path%\Config\Security.config

(user)C:\Documents and Settings\Tom Perkins\Application Data\Microsoft\CLR Security Config

Framework Tools to configure security files:

.NET Configuration Tool (MSCORCFG.MSC)

Core Access Security Policy Tool (CASPOL.EXE) Lesson 7

App Domains and Run-Time Hosts

Lesson 6

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App Domains

Application Failing

Application!

.NET Framework

Application

Application domains provide a secure, isolated, and fault-tolerant execution environment.

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Processes

• A process is the execution boundary within which an application runs.

• When process starts, run-time assigns an address space to it.

• Memory addresses within the process are assigned relative to process – Address space useless to other processes– Other apps cannot address this app’s data

• App is isolated; if it fails it leaves other apps unaffected

process

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JIT Compilation

• JIT compiler makes sure code references valid objects

• Makes sure only valid operations are performed on objects– “Type-safe” validation

• Validated code loaded into application domain

process

portable

executable

JITcompiler

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Application Domains

• Application domain: boundary in which an application operates

• Process can contain several application domains

• Can’t access another app domain’s code directly

• Proxy enables inter-domain communication

• Failure in one app doesn’t affect execution of app in another app domain

• You can start and stop an app in an app domain without affecting others in process

Application

Domain

Application

Domain

process

proxy

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Multi-Assembly Apps• App may need functionality from more than one

assembly• Both assemblies must be loaded into app domain

before execution can start• Shared assemblies can share code between two app

domains• Data is not shared between domains using a shared

assembly• Assembly shared between app domains said to be

domain neutral• Domain neutral assemblies may be more efficient,

but also slower• You can control whether assembly is loaded as

domain neutral

MyApp.exe MyUtil.dll

assembly

Class lib

assembly

App

domain

App

domain

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Run-Time Hosts• When app is invoked, run-time (CLR) is not

running in a process• Run-time host loads CLR into process • Run-time hosts for:

– ASP.NET– Shell executables– Internet Explorer components

• Run-time loads and initializes the CLR inside the process

• During load process, you can set whether or not runtime will host domain-neutral assemblies

CLR

App.exeRun-time

Host

Process

.NET Framework Tools

Lesson 7

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.NET FRAMEWORK TOOLS

• ASSEMBLY LINKER• IL ASSEMBLER• IL DISASSEMBLER• CODE ACCESS SECURITY POLICY

TOOL• .NET FRAMEWORK CONFIGURATION

TOOL

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ASSEMBLY LINKER

C# msil

.net module

VB msil

.net moduledll

resource

file

AL.EXE

Assembly

with

manifest

output from C# compiler

output from VB compiler

al [sources] [options]

al /t:exe /out:MyApp.exe /main:MyClass.Main MyModule.netmodule MyUtil.dll

input modules may not have an assembly manifest; output does

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ILASM -- MSIL ASSEMBLER

C# msil

.net module

VB msil

.net moduledll

resource

file

ILASM.EXE

Executable

(PE) File

output from C# compiler

output from VB compiler

Output in native code

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ILDASM – MISL DisassemblerPortable executable

File containing

MSIL code

ILDASM

MSIL (text) ILASM

May not contain

metadata

Use default GUI to view; use File|Dump option to save text file

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CASPOL – Code Access Security Policy Tool

• Allows users and administrators to grant and modify permissions for code groups at the user, machine, and enterprise policy levels

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MSCORCFG - .NET FRAMEWORK CONFIGURATION TOOL

• Manage and configure assemblies located in the GAC

• Manage code access security and remoting services

• To access this tool: Start|Control Panel | Administrative Tools | .Net Framework Configuration