1. Teaching with C Sharp
Rob Miles

2. Overview Introduction C# and Java Significant C# Features Conclusion
My perspective
C# and Java
Broad overview of the languages
Significant C# Features
C# features from a teaching perspective
Conclusion
..and possibly a sing song?

3. Introduction
The material is based on my experience teaching C# to two student cohorts
It is necessarily coloured by my teaching philosophy
It has been presented in targeted sections so that you can use those components which suit your purpose
There are number of sample projects for each section which form the basis of the lab work

4. Presentation Notes
A full set of notes is provided for this presentation
The notes are broken down in the same sequence as the items given here
Each section is followed by a number of practical examples along with some ideas for investigation

5. Bonus Materials As this is the “collectors edition” of the course
Just like every other edition…
It is supplied with bonus materials in the form of a copy of “C# from Java”
This provides an FAQ for a number of conversion issues

6. Teaching Philosophy At Hull we teach an “algorithms first” course
This concentrates on program construction in semester one and introduces objects in semester two
Everything is placed in the strongest possible “real world” context and I make heavy use of analogies

7. Objects Objects are presented as a solution to structure and design
I try to make a logical transition from structures to components:
Encapsulation
Business Objects
Test driven development
Component based design
Hierarchies for code reuse

8. Teaching and C#
I have found that C# matches with our teaching philosophy
It would also match with an objects first approach, at least as well as Java does
The points made later are applicable to both teaching approaches

9. C# and Java C# is heavily based on Java
Conversion from C# to Java (or back) is not difficult
C# programs seem to run faster on the PC platform
C# is not being positioned as Microsoft proprietary
But the language development is Microsoft driven, in the same way that Java development is Sun driven

10. C# Versions There are now two versions of C#
Version 2 adds a number of features:
Partial classes
Generics
There are few breaking changes moving from C# Version 1 to Version 2
This presentation is Version 1 compliant

11. Development Tools A command line compiler kit is available
Directly analogous to the JDK
Visual Studio 2005 is available under the Academic Alliance
Visual Studio 2005 Express Edition is available for free
David will give more details of these later

12. C# Language Features We can consider some specific C# features:
User input/Output
Value Types and Structures
Exception Handling
Reference Parameters
Event Handling/Delegates
Program Linking and Deployment
Properties
Generics
They will be placed into a teaching context

13. User input/output
The System.Console object provides a range of input/output actions
There is no need to create a stream object
There is also no need to trap exceptions

14. demo Simple Input/Output Console Power
Text Read and Write and colour manipulation
Console Power
Moving dot game
Use example 01 to read and write a couple of strings and show the text formatting/colour
Use example 02 to show the console text positioning etc

15. Value Types In Java a type is either primitive or reference: Primitive
Managed by value
Primitive types do not support methods or properties
Reference
Managed by reference
Support methods and properties
Slower to manipulate
A good description of generics here:

16. Java Primitive Problems
For a student learning to program the primitive-reference distinction is hard to grasp
It also brings a need to describe the use of wrapper classes
Students do not like to have to learn the difference between int and Integer
This knowledge is not that relevant to other languages

17. C# value types C# uses a different approach:
All types are objects
Some types are “value” types, i.e. manipulated by value not reference
But they all support methods and properties
The “box” operation performs conversion from value to reference as required
The C# student need not be aware of any distinction at the start of the course

18. demo Value type behaviour in .NET 1.1 and .NET 2.0
Using ildasm to look at the IL
Show the simple assignment demo. If there is time you can also use ildasm to look at the code

19. Boxing in Action static void Main(string[] args) { int a, b; a = 99;
Console.WriteLine("a is {0} b is {1}", a, b); }

20. Boxing Assembler

21. Structures as value types
C# supports a struct type
This type is directly analogous to the struct in C
A struct is manipulated as a value type
This allows data to be grouped together without a need to cover objects and references
It also allows for more complex exercises

22. C# Structs A struct in C# is managed by value.
However, they do behave a lot like objects
They can support methods and properties
They can have constructors
They can even implement an interface
But they do not support inheritance

23. demo Structures in C# Simple structures Structure “housekeeping”
Arrays of structures
Show the structures

24. Exception Handling
In Java you have to handle some exceptions (the checked ones)
These are thrown by lots of library methods, including input/output
In C# all exceptions are unchecked
If you don’t catch them the run time system will pick them up
This makes things like simple input/output much simpler

25. demo Exceptions in C# Simple exception handling
Creating your own exceptions
Show simple exception handling

26. Reference Parameters
Unlike Java, where parameters are always passed by value, in C# reference parameters are allowed
This makes programming more efficient
It also allows discussion of the meaning of references without the need to consider objects

27. demo Reference Parameters ref parameters in parameters
Show the structures

28. Event handling and delegates
C# provides a delegate type which can be used to create a typesafe reference to a method in an instance of a class
There is no need to create an instance of a class to receive events
Delegates are used to manage system events and the user interface

29. demo Event handling with delegates
Simple form creation and event management
Using the Visual Studio 2005 Forms Designer
Show the structures

30. Delegates and Design
Delegates bring function pointers back into programming
However, they can be deployed in a typesafe manner in a properly managed environment
However, he biggest advantage over Java is that they make interacting with Forms components much easier

31. Program Linking and Deployment
In Java a program is built at run time
The classpath is used to locate the required components as the program runs
There is little attention paid at build time to linking issues
In C# the .exe file is an assembly which may make use of .dll library files
There is a distinct difference between an executable file and a library one
An exe file will refer to a specific version of a dll when it is built

32. C# Programs
Only one class in a C# program may contain a Main method to provide the entry point
During the build process the particular libraries to be used must be specifically identified and located
If you are using Visual Studio the metadata from the assembly can be used in interactive help

33. C# Linking and Teaching
I place great emphasis on Business Objects and Test Driven Development
The C# linking process fits well with this approach
The students are initially introduced to the process by means of compiler directives
Later they move on to use Visual Studio 2005

34. demo Using Business Objects
Single workspace containing a number of Visual Studio Projects
Show the structures

35. The naming of components
Java provides a package mechanism by which a system can be broken down into components
this is linked to the physical position of the file in a directory hierarchy
only one public class can placed in each file, and the filename must match the class name
C# does not do this
A class is placed in a “namespace” which is not physically mapped to storage

36. C# Namespace Namespaces are hierarchical
A single source file can contain components from a number of namespaces
A namespace can span multiple source files
Visual Studio 2005 provides a view of all the components in a namespace

37. Partial Classes These are available in C# Version 2.0
A class can be made to span a number of source files
This allows the developer to partition the behaviours of a class into a number of separate source files
Hide the scary bits?
Visual Studio 2005 does this with forms

38. demo Using Business Objects and Namespaces
Advanced multi-project workspace with business and control objects
Show the structures

39. Properties Properties are “syntactic sugar”
They provide a convenient wrapper for get and set behaviour in objects
There is no need to use them
But all of the system library classes do
They are best explained in the context of “making life easier”

40. demo Simple Properties
A book title class which uses properties to manage the name of the book
Show the structures

41. Properties and Assembler

42. Generics Generics are new in Version 2.0
They let you create classes which work on classes
You don’t have to give the types of the classes when you write the code
Instead you use placeholders which are “filled in” at runtime in a typesafe manner

43. Generics and teaching
I would not teach about generics in the first part of a programming course
The fact that they are now present in C# means that we can use this language in later years

44. Generic Collections
The major advantage that generics brings for learner programmers is a better way to deploy collection classes
They remove the need to cast items read from the collection
Although I must admit I think that covering casting at this point is a good idea

45. demo Using the List collection class
A typesafe list collection is created using the new System.Generics.List collection class
Show the structures

46. Using Generics
Generics do make it possible to talk about data structures without dwelling on the type of the data being manipulated
This can be rolled into discussions about generalisation which can take place in the latter parts of a first year course

47. demo Creating and using a generic linked list class
A linked list generic which is deployed for both integers and string types
Show the structures

48. Conclusion Students like C#
We have seen improved performance in both coursework and examinations
It is a more productive programming environment than Java
All of the language changes are soundly pragmatic
The toolset is very effective and now handles important issues like test driven development
C# will do very nicely. For now……

49. Questions I can take any quick questions now
For more detailed ones please catch me in the break or during the labs