Assemblies

Objectives

•

Introduce assemblies – concept – creation – naming

• Discuss deployment

– main .exe – dependent assemblies

2

Assembly

• An assembly is a logical group of types

– unit of deployment, versioning, and security in the CLR

Invest

assembly of financial types

Stock

Bond

Advisor

3

Assembly contents

• Assembly contains several parts

– IL – description of contained types in the metadata – description of assembly in the manifest

IL

code for Invest, Stock, Bond, Advisor classes

metadata

description of Invest, Stock, Bond, Advisor classes

manifest

.ver 1.2.3.4 .publickey ...

4

Type access

• Two access levels available for types

– internal allows access only within same assembly (default) – public allows access from all assemblies

available only in assembly

internal class Advisor {

...

}

available in all assemblies

public class Stock {

...

}

5

Member access

• Can make type member internal

– allows access only within same assembly

public class Stock {

available only in assembly

internal string name; ...

}

6

Single file assembly

• Assembly can be single dll or exe file

– simple to create – simple to deploy – most common case

Finance.dll

single file assembly

Invest

Stock

Bond

Advisor

7

Assembly creation

• Compiler outputs assembly when target type is:

– exe – winexe – library

Invest.cs

Stock.cs Finance.dll

compiler

Bond.cs

Advisor.cs

source files

assembly

csc /target:library

/out:Finance.dll Invest.cs Stock.cs Bond.cs Advisor.cs

8

Module

• Can create module with compiler /target:module switch

– does not create assembly – typically has .netmodule extension

Stock.cs

Assets.netmodule

compiler

Bond.cs

source files

module

csc /target:module

/out:Assets.netmodule Stock.cs Bond.cs

9

Multi-file assembly

• Can create multi-file assembly

– use /addmodule compiler switch to add module to assembly – can also use more powerful assembly linker al.exe

Invest.cs Assets.netmodule

compiler

Advisor.cs Finance.dll

additional source files

two files, one assembly

csc /target:library

/out:Finance.dll /addmodule:Assets.netmodule Invest.cs Advisor.cs

10

Assembly identity

• Assembly identified by four attributes

– name – culture – version – public key token

11

Name

• Assembly name based on name of file containing manifest

– set automatically when assembly created

Finance.dll

compiler

assembly name is Finance

csc /target:library

/out:Finance.dll ...

12

Culture

• Assembly can specify optional target culture

– typical to have separate assembly for each supported culture – assembly will be culture neutral if culture not specified

• Culture typically specified using AssemblyCulture attribute

– in System.Reflection namespace

[assembly: AssemblyCulture("fr-CA")]

French-Canada

13

Version

• Assembly can be given a four part version number

– major version – minor version – build number – revision

• Version typically specified using AssemblyVersion attribute

– in System.Reflection namespace

[assembly: AssemblyVersion("1.2.3.4")]

major.minor.build.revision

14

Public key token

• Public/private key pair used to give assembly a strong name

– used in deployment to provide unique identity – hash of public key called token used since public key is long

• Procedure:

– generate public/private key pair with strong name tool sn.exe – apply to assembly with AssemblyKeyFile attribute – attribute is in System.Reflection namespace

sn -k Lib.snk

generate keys, specify output file

[assembly: AssemblyKeyFile("Lib.snk")]

apply keys to assembly

15

Dependent assemblies

• Typical for application to consist of multiple assemblies

– main .exe and supporting .dlls

App.exe

Finance.dll

Invest

Stock Main

Bond

main .exe

supporting .dll

Advisor

16

Compile time assembly reference

• Can use type defined in other assembly

– must compile with option /r[eference]:

• Compiler searches for referenced assemblies

– current directory – CLR system directory – directories specified by /lib:dir1[,dir2...] switch – directories specified by LIB environment variable

App.cs App.exe

compiler

csc /target:exe

/out:App.exe /reference:Finance.dll App.cs

17

Dependent assembly reference

•

Identity of dependent assemblies recorded in manifest – information used during runtime assembly binding – ensures binding to same assembly at runtime

App.exe

.assembly extern Finance {

dependent assembly recorded

.publickeytoken ... .ver 1.2.3.4

}

...

18

Deployment

• Several actors involved in deployment

– main .exe – dependent .dlls – main deployment directory – configuration file

19

AppBase

• Directory containing main .exe called AppBase

C:\

Program Files

AppBase

MyApplication App.exe

20

Application configuration file

• Application can have configuration file – used to help manage deployment – file name is application name with .config added – placed in AppBase

App.exe.config file in AppBase directory

...

21

Deploying dependent assemblies

• Several options for deployment of dependent assemblies

– AppBase – directory below AppBase specified in config file – local or remote location specified by URI in config file – global assembly cache

22

AppBase deployment

• AppBase automatically searched for needed assemblies

C:\

Program Files

AppBase

MyApplication

dependent assembly

App.exe Finance.dll

23

Private path

• Can specify subdirectories of AppBase be searched

– use probing privatePath in config file

C:\

Program Files

AppBase

MyApplication

App.exe App.exe.config

MyAssemblies

Finance.dll

dependent assembly

24

Codebase

• Can specify arbitrary URI for strongly named assembly

– use codeBase element in config file – useful to redirect to new version of needed assembly

C:\

Program Files

MyAssemblies MyApplication

not under AppBase dependent assembly

Finance.dll App.exe App.exe.config

25

Global assembly cache (gac)

• Strongly named assembly can go in global assembly cache

– typically stored under C:\Windows\assembly – need admin privileges to install – automatically searched for needed assemblies – use gacutil tool to manipulate cache • Convenient way to store shared assembly

– but complicates deployment, backup, and uninstall

gacutil /i Finance.dll install

gacutil /u Finance,Version=1.2.3.4,PublicKeyToken=362cfdd636584143 uninstall

26

Summary

• Assembly is the component of the CLR – unit of deployment and versioning

• Assembly identity made of four components

– name – culture – version – public key token

• Application typically made of several assemblies

– must reference dependent assemblies at compile time – several options for runtime assembly deployment

27