C#’s Family Tree

1. C#

2. C#’s Family Tree • C# inherits a rich programming legacy from C (1972) and C++ (1979). • It is closely related to Java (1991).

3. A Faster Start • C# does NOT require the use of pointers, object destructors, and the use of #include • Command prompt or Visual Studio IDE • No String[] args needed in main method header as in Java (optional) • Class name does not have to match file name • Can use .exe name to execute in the command line interface • File can contain multiple classes

4. Object Oriented Language • Methods and variables in object-oriented programming are encapsulated, that is, users are only required to understand the interface and not the internal workings of the class • Polymorphism and Inheritance are two distinguishing features in the object-oriented programming approach • Polymorphism describes the ability to create methods that act appropriately depending the context • Inheritance provides the ability to extend a class so as to create a more specific class

5. Similarities and Differencesfrom C++ and Java • Functions are called Methods • main() becomes Main() • Namespace - class - object - method relationship introduced early • Save files with .cs extension • writeln() becomes WriteLine() Hello.cs Hello2.cs

6. Writing a C# Program that Produces Output • “This is my first C# program” is a literal string of characters • The string appears in parenthesis because it is a parameter or an argument • The WriteLine() method prints a line of output on the screen

7. Writing a C# Program that Produces Output • Out is an object that represents the screen • The Out object was created and endowed with the method WriteLine() • Not all objects have the WriteLine() method

8. Writing a C# Program that Produces Output • Console is a class • Console defines the attributes of a collection of similar “Console” objects

9. Writing a C# Program that Produces Output • System is a namespace, which is a scheme that provides a way to group similar classes • Namespaces are used to organize classes

10. Compiling and Executing a Program from the Command Line • After creating source code, you must do the following before you can view the program output: • Compile the source code into intermediate language (IL) • Use the C# just in time (JIT) compiler to translate the intermediate code into executable statements

11. Selecting Identifiers • Every method used in C# must be part of a class • A C# class name or identifier must meet the basic following requirements: • An identifier must begin with an underscore or a letter • An identifier can contain only letters or digits, not special characters #,$, or & • An identifier cannot be a C# reserved keyword

12. Variables • All variables are objects • As objects, all types have built-in methods • Creating formatted output is easy Variables.cs • Characters are not one byte, they are two bytes due to Unicode (0 to 65535) • Global Portability

13. Data Types

14. More Integer Data Types

15. Other Data Types

16. Using the String Type • The Equals Method returns True or False • The Compares Method returns a zero if two words are the same, a positive number if the first word is greater than the second, and a negative number if the first word is less than the second. Strings.cs

17. New Data Types • byte = 1 byte Range = 0 to 255 • sbyte = 1 byte Range = -128 to 128 • Decimal – for monetary calculations • Range 1E - 28 to 7.9E + 28 Decimal.cs • C++ often was subject to a variety of rounding errors. The decimal data type can accurately represent up to 28 decimal points.

18. Formatting Output

19. Example of Formatting • Console.WriteLine(“Floating Amount: {0,0:$###.##}, 3.14); • Prints: Floating Amount: $3.14 • Console.WriteLine(“Floating Zeros: {0,0:$000.00}, 3.14); • Prints: Floating Amount: $003.14

20. Formatting Output Cont.

21. Examples of Formatting double someMoney = 123; string moneyString; moneyString = someMoney.ToString("F"); Console.WriteLine(moneyString); moneyString = someMoney.ToString("F3"); Console.WriteLine(moneyString); Console.WriteLine(someMoney.toString("C2") The first WriteLine() statement in the following code produces 123.00, the second produces 123.000, and the third produce $123.00.

22. Using the string Data Type to Accept Console Input • You can use the Console.ReadLine() method to accept user input from the keyboard. • This method accepts all the characters a user enters until the user presses Enter. The characters can be assigned to a string. • For example, the statement: myString = Console.ReadLine(); accepts a user’s input and stores it in the variable myString.

23. Boolean Variables • Values are true/false (no 1/0 like C++) • If statements must use == for equivalency • If you fail to use ==, it will not compile • Attempting to use an uninitialized variable If.cs

24. Relational Operators

25. Escape Sequences

26. Time for You to Try! • Temperature Conversion Program • Allow the User to Input a Fahrenheit temperature and convert it to Celsius • Result should go out 2 decimal places • Formula = (F - 32) x (5/9) • Test Data = 90° F is 32° C

27. If Statement • Like C++ and Java IfElseDecision.cs IfElseDecisionWithInput.cs • Comments can be written 3 ways • /* The old C way –Block Comments */ • // The C++ way – Line Comments • /// The XML way

28. Logical Operators 28

29. Making Decisions Using the switch Statement • The switch structure uses four new keywords: • switch starts the structure and is followed immediately by a test expression • case is followed by one of the possible values that might equal the switch expression • break optionally terminates a switch structure at the end of each case • default optionally is used prior to any action that should occur if the test expression does not match any case

30. Switch Statement • No fall-through rule Switch.cs

31. Loops • While Loop • Do While Loop • For Loop A loop is a structure that allows repeated execution of a block of statements

32. Using the while Loop • You can use a while loop to execute a body of statements continuously while some condition continues to be true • A while loop consists of the keyword while, followed by a Boolean expression within parentheses, followed by the body of the loop • A loop that never ends is called an infinite loop

33. Using the while Loop • To make a while loop end, three separate actions should occur: • Some variable, the loop control variable, is initialized • The loop control variable is tested in the while statement • The body of the while statement must take some action that alters the value of the loop control variable

34. Using the for Loop • A loop that executes a specific number of times is a definite loop or a counter loop • When you use a for statement, you can indicate the starting value for the loop control variable, the test condition that controls loop entry, and the expression that alters the loop control variable

35. Using the for Loop • The three semicolon separated sections of a for statement are used for: • Initializing the loop control variable • Testing the loop control variable • Updating the loop control variable

36. Using the for Loop Printing integers 1 through 10 with while and for loops

37. Methods • All methods must have an explicit return type • No int default when returning variables • Methods can have four types of arguments: Value ParameterDemo1.cs Reference ParameterDemo2.cs Output ParameterDemo3.cs Params ParameterDemo4.cs

38. Overloading Methods • Overloading involves using one term to indicate diverse meanings • When you overload a C# method, you write multiple methods with a shared name • The compiler understands the meaning based on the arguments you use with the method

39. Overloading Methods • An overloaded method

40. Initializing an Array • Arrays, like object fields, have default values • You can assign nondefault values to array elements upon creation • Examples: int[] myScores = new int[5] {100,76,88,100,90}; int[] myScores = new int[] {100,76,88,100,90}; int[] myScores = {100,76,88,100,90};

41. Arrays • Arrays must be declared with brackets after the type: int[] numbers = new int[20]; • Can use foreach statement (like VB) ForEach.cs • Params Params.cs

42. Arrays • "Extra" array elements are not initialized to 0 • IndexOutOfBoundsException becomes IndexOutOfRangeException • You can change an array's size int[] nums = new int[5]; nums = new int[10];

43. Garbage Collection • No need for a delete command to clear up dynamic arrays • C#’s garbage collection reclaims object space automatically behind the scenes • For efficiency, C# only runs the garbage collection feature when: • There are objects to recycle • There is a need to recycle them

44. The BinarySearch() Method • The BinarySearch() method finds a requested value in a sorted array • This method accepts two arguments: an array, and the field to be searched for • The method returns –1 if the value is not found in the array, otherwise it returns the index where the value is located

45. The BinarySearch() Method • This method does NOT work under the following conditions: • If the array items are not arranged in ascending order, the BinarySearch() method does not work correctly • If the array holds duplicated values, then the BinarySearch may not work • If you want to find a range match rather that an exact match, the BinarySearch() method does not work

46. The BinarySearch() Method • BinarySearch program

47. Using the Sort() and Reverse() Methods The Sort() method arranges array items in ascending order

48. Using the Sort() and Reverse() Methods The Reverse() method reverses the order of items in an array

49. Using the Sort() and Reverse() Methods Output of MyTestScores

50. Classes • Static members cannot be used with objects • Built-in components have "natural" names - e.g., Label, not JLabel • No multiple constructors for components like Label, Button, etc.