1. INF230 Basics in C# Programming
AUBG, COS dept
Lecture 29
Title:
DLL libraries, ILDASM
(part 1)
Reference: Doyle, chap 11

2. Chapter 11 Advanced Object-Oriented Programming Features
C# Programming:
From Problem Analysis to Program Design
4th Edition

3. Lecture Contents: OOP Features (reminder) Advanced OOP features.
Abstraction , Encapsulation, Inheritance, Polymorphism, Generics
Advanced OOP features.
Component-Based Development
Multi tier apps – Business, Presentation, Data layers, components
Using libraries DLL to implement components

4. Object-Oriented Language Features
Abstraction
Generalizing, identifying essential features, hiding nonessential complexities
Encapsulation
Packaging data and behaviors into a single unit, hiding implementation details
Inheritance
Extending program units to enable reuse of code
Polymorphism
Providing multiple (different) implementations of same named behaviors
C# Programming: From Problem Analysis to Program Design

5. Component-Based Development
Figure Component-based development
C# Programming: From Problem Analysis to Program Design

6. Component-Based Development (continued)
Component-based applications associated with multitier applications – (different layers)
Business layer(s) – classes that perform processing
Provide functionality for specific system; provide necessary processing
Data access layer - classes for accessing data from text files and databases
Presentation layer - User interface tier for user interaction
Graphical User Interface such as Windows or Web
C# Programming: From Problem Analysis to Program Design

7. Component-Based Development (continued)
Components facilitates reuse-based approach
Define and implement independent components into systems
Components are implemented through classes
Takes the form of objects or collection of objects
Components can then be packaged with different components and used for other applications
Classes can be created that extend functionality of original classes
C# Programming: From Problem Analysis to Program Design

8. Component-Based Development (continued)
SW products structure classification
Logical structure
Multi tier organization – UI layer, business layer, DB access layer
Physical structure
All components in sole package/module/file: NO SW reusability
Components saved in a container prepared for reusability in many applications
Most often container is organized as a library – static (.lib) or dynamic (.dll)
C# Programming: From Problem Analysis to Program Design

9. DLL and ILDASM THE NEED of DLL as container of reusable code fragments
(present lecture)
The need of program tools to explore code fragments
(next lecture)

10. Run
Demo programs on DLL

11. Details on Compilation
The C# compiler compiles source code (as a set of files with .cs as an extension) into an assembly.
An assembly is the unit of packaging and deployment in .NET.
An assembly can be either an application or a library.
A normal console or Windows application has a Main() method and is an .exe file.
A library is a .dll file and is equivalent to .exe without an entry point. Its purpose is to be called upon (referenced) by an application or by other libraries.
C# Programming: From Problem Analysis to Program Design

12. Creating DLL

13. Dynamic Link Library (DLL)
Several alternate options for creating components
One option – compile source code into .dll file type
Once you have DLL, any application that wants to use it just adds a reference to the DLL
That referenced file with the .dll extension becomes part of the application’s private assembly
First way: Can use the command line to create DLL
C# Programming: From Problem Analysis to Program Design

14. A. Using command line to create DLL files
To create DLL from MS VS cmd prompt. You get it:
Start>All Programs>MS VSxx>VSTools>Developer Cmd prompt for VSxx
At the cmd prompt you should type cmd like this:
csc /target:library /out:Counter.dll Counter.cs
You can specify more input files
csc /target:library /out:Counter.dll Counter.cs P1.cs P2.cs
Option /target:library makes compiler to generate .dll instead .exe
Option /out may omit. Then output file is named after first listed source
C# Programming: From Problem Analysis to Program Design

15. Dynamic Link Library (DLL)
Using command line to create DLL files
csc /target:exe build a console executable
csc /target:winexe build Windows executable
csc /target:library build a library
csc /target:module build a module that can be added to another assembly
C# Programming: From Problem Analysis to Program Design

16. B. Using VS to create DLL files
Second way: more user friendly and attractive from within VS. You should select Class Library template for a project
C# Programming: From Problem Analysis to Program Design

17. Building instead of Running Project
The source code that you type includes one or more class definitions. These classes have no Main() method within them.
To compile and create DLL, you select options under Build menu:
Build > Build Solution
Build > ReBuild Solution
C# Programming: From Problem Analysis to Program Design

18. Client App to use the DLL
Creating
Client App to use the DLL

19. Creating a Client App to use DLL
The created DLL can be reused with many different apps.
You need to do two steps to use the DLL
First: to add a reference to the components in your program
Second: to include using directive with the appropriate namespace
C# Programming: From Problem Analysis to Program Design

20. Sample Demo Projects INF230CreateLibrary INF230UsePrivateLibrary
The project name identifies the library name, i.e. this project creates file INF230CreateLibrary.dll
INF230UsePrivateLibrary
The client project needs to include:
using INF230CreateLibrary; // namespace directive
To add a reference from within the project to the newly created user dll
C# Programming: From Problem Analysis to Program Design

21. Sample Demo Projects DLLCreateClassLibrary DLLUseClassLibrary
The project name identifies the library name, i.e. this project creates file DLLCreateClassLibrary.dll
DLLUseClassLibrary
The client project needs to include:
using DLLCreateClassLibrary; // namespace directive
To add a reference from within the project to the newly created user dll
C# Programming: From Problem Analysis to Program Design

22. Build Instead of Run to Create DLL
Create the parent class first in order to use IntelliSense (for sub classes)
To illustrate creating stand-alone components, separate project created for Person and Student
Because Visual Studio assigns the namespace name the same name as the project name (Person), you should change the namespace identifier
If you don’t change it, when you start adding a reference to a created DLL, it can become confusing
Changed to PersonNamespace for the example
C# Programming: From Problem Analysis to Program Design

23. Build Instead of Run to Create DLL
After typing class, do not run it – select BUILD, Build Solution
Figure Attempting to run a class library file
Create new project for subclasses (Student)
Again, select Class Library template from Start page
Change namespace identifier (StudentNamespace)
C# Programming: From Problem Analysis to Program Design

24. Build Instead of Run to Create DLL (continued)
Add a new using statement to subclass
In Student, add using PersonNamespace;
To gain access to base class members in subclass, Add Reference in subclass to base class
Use Solution Explorer window
DLL is stored in Debug directory under the bin folder wherever you create the project
C# Programming: From Problem Analysis to Program Design

25. Add Reference to Base Class
One of the first things to do is Add a Reference to the Parent DLL
Figure Adding a reference to a DLL
C# Programming: From Problem Analysis to Program Design

26. Add Reference to Base Class (continued)
Use Browse button to locate DLL
Figure Add Reference dialog box
C# Programming: From Problem Analysis to Program Design

27. Add Reference to Base Class (continued)
Figure Locating the Person.dll component
C# Programming: From Problem Analysis to Program Design

28. Adding a New Using Statement
In the subclass class, if you simply type the following, you receive an error message
public class Student : Person
Figure Namespace reference error
C# Programming: From Problem Analysis to Program Design

29. Adding a New Using Statement (continued)
Notice fully qualified name
To avoid error, could type:
public class Student : PersonNamespace.Person
Better option is to add a using directive
using PersonNamespace; // Use whatever name you
// typed for the namespace for Person
After typing program statements, build the DLL from the Build option under the BUILD menu bar
C# Programming: From Problem Analysis to Program Design

30. Creating a Client Application to Use the DLL
DLL components can be reused with many different applications
Once the component is in the library, any number of applications can reference it
Instantiate objects of the referenced DLL
Two steps Required
Add a reference to the DLL components
Include a using statement with the namespace name
C# Programming: From Problem Analysis to Program Design

31. Creating a Client Application to Use the DLL (continued)
Figure DLLs referenced in the PresentationGUI class
C# Programming: From Problem Analysis to Program Design

32. Practical session Creating DLL Creating a client app to use the DLL
C# Programming: From Problem Analysis to Program Design

33. Classes as DLL contents
Project ClassLibrary3
Contains class Counter definition
Contains class Distance definition
File ClassCountDistDefined.cs
Project ClassLibrary3UsedBySB
Contains references to Counter class
Contains references to Distance class
File ClassCountDistUsed.cs
C# Programming: From Problem Analysis to Program Design

34. Classes as DLL contents
Compile and run a pair of projects based on DLL ClassLibrary3
C# Programming: From Problem Analysis to Program Design

35. Structures as DLL contents
Project ClassLibrary4
Contains struct Book definition
File StructBookDefined.cs
Project ClassLibrary4UsedBySB
Contains references to Book struct
File StructBookUsed.cs
C# Programming: From Problem Analysis to Program Design

36. Structures as DLL contents
Compile and run a pair of projects based on DLL ClassLibrary4
C# Programming: From Problem Analysis to Program Design

37. Interfaces as DLL contents
Project ClassLiIbrary5
Contains interface ITraveler definition
File ITravelerDefined.cs
Project ClassLibrary5UsedBySB
Contains references to Itraveler interface
File ITravelerUsed.cs
C# Programming: From Problem Analysis to Program Design

38. Interfaces as DLL contents
Compile and run a pair of projects based on DLL ClassLibrary5
C# Programming: From Problem Analysis to Program Design

39. Thank You
For
Your Attention!

40. Using ILDASM to View the Assembly
(ILDASM): Intermediate Language Disassembler tool
Assembly shows the signatures of all methods, data fields, and properties
One option – display the source code as a comment in the assembly
Can be run from the command line or from within the Visual Studio IDE
C# Programming: From Problem Analysis to Program Design

41. Using ILDASM to View the Assembly (continued)
In order to use ILDASM in Visual Student, must be added as an external tool in Visual Studio (TOOLS, External Tools…)
DLL files cannot be modified or viewed as source code
Can use ILDASM to view DLL assemblies
C# Programming: From Problem Analysis to Program Design

42. ILDASM to View the Assembly
.ctors are constructors
IL code for the method
Data fields
Properties converted to methods
Figure Student.dll assembly from ILDASM
C# Programming: From Problem Analysis to Program Design

43. Thank You
For
Your Attention!