Introductory Programming with C#

1. Introductory Programmingwith C# Judith Bishop University of Pretoria, South Africa Visiting TU-Berlin Microsoft Courses 2003

2. Talk overview • Introduction • Who, why, when, how, with what? • Syntax and semantics • for you and your students • A tour through some lessons • Early concepts • Our approach to GUIs • Debugging • Advanced concepts • Assessment • Quizzes, exercises, laboratories, exams • References Microsoft Courses 2003

3. Featuring … • Syntax and semantics descriptions • Early use of libraries • Independent GUI specifications • Debugging New Microsoft Courses 2003

4. Focus on C# • Designed by Anders Hejlsberg, Scott Wiltamuth and Peter Golde • To b the main development medium for future Microsoft products • Origins in C++, Java, Delphi, Modula-2, Smalltalk • Heljsberg was the chief architect behind Turbo Pascal and Delphi • Standardised by Ecma and ISO • Free (to us) Microsoft Courses 2003

5. Changing languages • Major movements worldwide • To Pascal in 1970s and 1980s • To Java in 1990s • Caused by advances in technology • Data structures, oops, internet computing • Foundation for later courses • Desire to be "ahead of the pack" • Inhibitors to change • Lack of teaching resources • Computing resources required by new technology • Investment in current language • Uncertainty over the measure of improvement Microsoft Courses 2003

6. A first programming course • Typically 40-50 lectures • 10-14 laboratories • Take home assignments • Project • Questions: • where does it start? • where does it end? • what is the place of libraries? • what is the order of topics? • what should be included/left out? • what do I need to run the language? Microsoft Courses 2003

7. Where does it start and end? • Most institutions assume "no background" • most students have more than that • use of computers is almost universal now • students can interact with GUIs • Strong desire to have "objects first" • but what is second? • what do objects assume? • With or without GUIs? • huge tension between need to program realistically and the number of concepts required to express GUIs • Advanced topics can be left to other courses • networking and databases - NetCentric Computing • generics and overloading - Data Structures Microsoft Courses 2003

8. What about libraries? • Libraries cannot be ignored, • More in the libraries than in the language! • Without them, examples will be too constrained • Students can be on a "need to know basis", BUT they need to know the structure and organisation of libraries • This knowledge transcends languages • Early use of libraries introduces many fundamental concepts in a controlled manner, e.g. • variables vs properties • instance vs static • constructors • parameters Microsoft Courses 2003

9. An order of topics • Introduction to computers, languages and compiling 2 • Using types 5 • Defining types 5 • Data structures and control structures 5 Views System 4 • Input and output with files 4 Debugging 3 • Collections 5 • Extensibility and polymorphism 5 • Extra topics 2 Half way Microsoft Courses 2003

10. What to include? • If a feature is covered, cover it completely, albeit over time in a spiral fashion • Include • images as data types - adds to the fun • GUIs - for realism • formatting and unicode - promotes internationalisation • serialization - makes for serious programs • exception handling - makes for robust programs • foreach loop - so neat and powerful • collections - enhance object-orientation Microsoft Courses 2003

11. What to exclude? • What to exclude depends on • length of course • interface with other courses • A suggestion • threads - in Operating Systems • networking - for Netcentric Computing • graphics and delegates - to introduce non-Views GUIs • operator overloading, other upcoming features (e.g. generics), - in Data Structures • Notes: • Topics that were in a Java introductory course might not be in a C# version (applets) • NOTE: some institutions will start with Netcentric Computing - interesting approach Microsoft Courses 2003

12. What resources do I need? • Microsoft Academic Alliance, plus • Option 1 (Student): • a PC • C# compiler • Any simple editor • Option 2 (Lecturer) • a PC with lots of memory • Visual Studio • Option 3 (Researcher) • PC or Mac, Windows or Linux • Rotor • Any simple editor Microsoft Courses 2003

13. C# Concisely • First year programming text book, Oct 2003 • Pearson, 2004 • Incorporates Views • Reviewed by Microsoft • Contents on the Views website http://csharp.cs.uvic.ca Microsoft Courses 2003

14. Volunteers on a C# course in Africa Do it in C# Naturally! Microsoft Courses 2003

15. From the ECMA C# Specification 8.7.4 Properties A property is a member that provides access to a characteristic of an object or a class. Examples of properties include the length of a string, the size of a font, the caption of a window, the name of a customer,and so on. Properties are a natural extension of fields. Both are named members with associated types, and the syntax for accessing fields and properties is the same. However, unlike fields, properties do not denote storage locations. Instead, properties have accessors that specify the statements to be executed when their values are read or written. Properties are defined with property declarations. The first part of a property declaration looks quite similar to a field declaration. The second part includes a get accessor and/or a set accessor. In the example below, the Button class defines a Caption property. public class Button { private string caption; public string Caption { get { return caption; } set { caption = value; Repaint(); } }} Microsoft Courses 2003

16. Syntax forms in C#C Fixed words and symbols Items to fill in public string Course { get {return course;} } Microsoft Courses 2003

17. Also for libraries Microsoft Courses 2003

18. Visual Studio Help Microsoft Courses 2003

19. Concepts for simple oops Microsoft Courses 2003

20. Example sequence from early lessons • Example 2.5 (page 45) - Meeting times • Creates objects of type DateTime and accesses their properties and methods • Example 2.6 (page 47) - Dates in different formats • Further example of DateTime methods, customising output • Example 2.7 (page 49) - Time with reading • Introduces input using Console and the Parse methods of a type • Example 3.4 (page 83) - Table of meeting times • Using a loop to create different times • Examples 3.2 and 3.3 (page 75) - The shuttle bus • Defining a type from scratch and using it in a program Microsoft Courses 2003

21. GUIs • Current approaches do not emphasise independent principles OPTIONS • Create GUIs by hand • error prone • takes too much time • Use a GUI builder • dumps code in the program • hides principles Microsoft Courses 2003

22. Views Where GUIs are going The reality of a single cross-language, cross-platform GUI interface programming model is in sight, based on an XML description language supported by fast native runtimes. [Russel Jones, DevX, Nov 2002] Microsoft Courses 2003

23. … and more recently Supporting many GUIs isn't just a simple process of including one set of libraries or another; it's often a frustrating and error-prone exercise in writing GUI-specific code. [Russel Jones, DevX, Aug 2003] Microsoft Courses 2003

24. JScript C# Rotor CLI Implementation VS.NET System.Web (ASP.NET) System.WinForms System.WinForms System.Drawing System.Data (ADO.NET) System.Xml SDK Tools System Common Language Runtime Platform Abstraction Microsoft Courses 2003

25. Views • Views is a Vendor Independent Extensible Windowing System • Developed by Nigel Horspool and Judith Bishop with help from students in 2002-2003 • Provides an XML-based specification notation for defining GUIs, and an execution engine for handling event listening and dispatching back to the program • It was supported under the Microsoft Rotor RFP Program • It is distributed from the C# Concisely book website Microsoft Courses 2003

26. Microsoft Courses 2003

27. Example in WinForms show.Click += new EventHandler(ActionPerformed); hide.Click += new EventHandler(ActionPerformed); } public void ActionPerformed(Object src, EventArgs args) { if (src == show) { pic.Show(); } else if (src == hide) { pic.Hide(); } }i • Embedded in 115 lines of generated code - “do not touch” • Unexplained classes and unused objects here Microsoft Courses 2003

28. widget rendering in the OS widget calls in a language Windows GUI Builder Application Add Listeners Handlers Visual Studio C# GUI building today Microsoft Courses 2003

29. widget rendering in the OS GUI XML Spec Application Control Engine Handlers Add Listeners A GUI using XML Microsoft Courses 2003

30. Example in Views XML Views.Form f = new Views.Form(@"<Form> <vertical> <horizontal> <Button Name=Show/> <Button Name=Hide/> </horizontal> <PictureBox Name=pic Image='C:Jacarandas.jpg' Height=175/> </vertical> </Form>" ); string c; for (;;) { c = f.GetControl(); PictureBox pb = f["pic"]; switch (c) { case ”Show" : pb.Show(); break; } case ”Hide" : pb.Hide(); break; } } } C# • No pixel positioning • No generated code • Separation of concerns Microsoft Courses 2003

31. Example 2 Views.Form v = new Form (@"<form Text= Lucky> <vertical> <TextBox name =Number Text = '13'/> <Button name = Start/> <ListBox name = Day Width = 270/> </vertical> </form>"); int luckyNumber = int.Parse(v.GetText("Number")); Random r = new Random (luckyNumber); for( ; ; ) { string s = v.GetControl( ); if (s==null) break; DateTime luckyDate = new DateTime(DateTime.Now.Year, r.Next(3,12);, r.Next(1,30);); v.PutText("Day", "Your lucky day will be " + luckyDate.DayOfWeek + " " + luckyDate.ToString("M")); } Microsoft Courses 2003

32. Other Views examples • Calculator • Compare with text version • Separation of concerns • Internationalization • PhotoAlbum • Fun with pictures Microsoft Courses 2003

33. Debugging • Principles - types of errors: • syntactic • semantic • runtime • Exception handling • Robust code • simple logic • validity checks - also with Assert • tracing statements • Debugger programs • Text based, or • GUI, with or without Visual Studio Microsoft Courses 2003

34. Oops in C# • Structs and classes • Well defined collection library • Array class • Sorted lists • BitArray • Queue, Stack, Hashtable • Polymorphism and extensibility • Interfaces and inheritance Microsoft Courses 2003

35. Example - Access control • Page 318 • Students, staff, posgrads and tutors have different rules for access to a building. The rules are implemented at the start of each year. • Polymorphic collection over IAccess • Classic simple data update example • Can be much extended e.g. for • serialisation • images Microsoft Courses 2003

36. Assessment • Quizzes • available online on the website • Exercises • at the end of each chapter - answers will be provided to lecturers • Practicals • worksheets are being devised based on the book • Exam questions • samples will also be provided Watch for the CD Microsoft Courses 2003

37. References • Peter Drayton, Ben Albahari, Ted Neward, C# in a Nutshell, O’Reilly, 2002 • Troelsen, Andrew “C# and the .NET platform” A! press 2001 • Damien Watkins, Mark Hammond and Brad Abrams, Programming in the .NET environment, Microsoft .NET Development Series, Addison Wesley, 2002 • Not many text books yet, but many trade books • Visual Studio help files • DevHood tutorials -- see http://www.devhood.com • http://www.cs.up.ac.za/rotor -- for the Views project Microsoft Courses 2003

38. Motivation for a different approach • Forward looking • Move to platform independent GUI systems • Integration of XML into languages (cf XEN) • Technical • Rotor does not have a GUI capability • Interesting challenges in Reflection, RegEx etc • Educational • Dissatisfaction with method-oriented or drag and drop GUIs • Separation of concerns Microsoft Courses 2003

39. The Views Notation form: <form>controlGroup</form> controlGroup: <vertical>controlList</vertical> | <horizontal>controlList</horizontal> controlList: { control } textItemList: { <item> text </item> } control: controlGroup | <Button/>| <CheckBox/> | <CheckedListBox> textItemList </CheckedListBox> | <DomainUpDown> textItemList </DomainUpDown> | <GroupBox>radioButtonList</GroupBox> | <Label/>| <ListBox/> | <OpenFileDialog/> | <SaveFileDialog/> | <PictureBox/> | <TextBox/> | <ProgressBar/> | <TrackBar/> radioButtonList: { <RadioButton/> } Microsoft Courses 2003

40. Handler methods Essentially five kinds of methods: construct close getControl get put PLUS … direct access Form(string spec,params) The constructor. void CloseGUI( ) Terminates the execution thread string GetControl( ) Waits for the user to perform an action string GetText(string name) Returns the value of the Text attribute int GetValue(string name) Returns the Value attribute from TrackBar, ProgressBar and CheckBox int GetValue(string name, int index) Returns the status of CheckBox at position index void PutText(string name, string s) Displays the string in a TextBox or ListBox control. void PutValue(string name, int v) Sets an integer value associated with a ProgressBar or CheckBox Microsoft Courses 2003

41. Handler methods Essentially five kinds of methods: construct close getControl get put PLUS … direct access Form(string spec,params) The constructor. void CloseGUI( ) Terminates the execution thread string GetControl( ) Waits for the user to perform an action string GetText(string name) Returns the value of the Text attribute int GetValue(string name) Returns the Value attribute from TrackBar, ProgressBar and CheckBox int GetValue(string name, int index) Returns the status of CheckBox at position index void PutText(string name, string s) Displays the string in a TextBox or ListBox control. void PutValue(string name, int v) Sets an integer value associated with a ProgressBar or CheckBox Microsoft Courses 2003

42. D1(P) D2(Q) D3(R) F(D1) -- calls P via M F() -- calls M F() -- calls M I D A M M M A B A C B B C P Q R M M M M M Object orientation • Extension, polymorphism • Delegation C Delegates Interfaces Inheritance Microsoft Courses 2003

43. widget rendering in the OS widget calls in a language Windows GUI Builder Application Add Listeners Handlers Visual Studio C# GUI building today Microsoft Courses 2003