1. 2: Basics
Basics
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

2. Objectives Introduce the core C# language features class Main types
2: Basics
Objectives
Introduce the core C# language features
class
Main
types
variables
basic input and output
operators
arrays
control constructs
comments
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

3. Class Keyword class used to define new type specify name
2: Basics
Class
Keyword class used to define new type
specify name
enclose body in { }
Most C# code placed inside a class
no global variables allowed
no global methods allowed
class definition
class MyApplication {
... }
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

4. Main Main method is the application entry point
2: Basics
Main
Main method is the application entry point
must be static method of some class
any access level such as public or private is allowed
Main can perform environment interaction
can receive command line arguments as array of strings
can return int to indicate success/failure
class MyApplication {
static void Main()
... }
entry point
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

5. Simple types Comprehensive set of simple types available Type
2: Basics
Simple types
Comprehensive set of simple types available
Type
Description
Special format for literals
bool
Boolean
true false
char
16 bit Unicode character
'A' '\x0041' '\u0041'
sbyte
8 bit signed integer
none
byte
8 bit unsigned integer
short
16 bit signed integer
ushort
16 bit unsigned integer
int
32 bit signed integer
uint
32 bit unsigned integer
U suffix
long
64 bit signed integer
L or l suffix
ulong
64 bit unsigned integer
U/u and L/l suffix
float
32 bit floating point
F or f suffix
double
64 bit floating point
no suffix
decimal
128 bit high precision
M or m suffix
string
character sequence
"hello"
Boolean
character
integer
floating point
string
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

6. Local variable declaration
2: Basics
Local variable declaration
Declare variables by specifying type and name
names are case sensitive
comma separated list for multiple variables
end with semicolon
class MyApplication {
static void Main()
double area;
char grade;
int x, y, z;
string name;
... }
variables
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

7. Local variable initialization
2: Basics
Local variable initialization
Can initialize local variables when declared
use literal value or expression
compiler error to use without initializing
class MyApplication {
static void Main()
int width = 2;
int height = 4;
int area = width * height;
int x;
int y = x * 2;
... }
literals
expression
error, x not set
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

8. Type conversion Some automatic type conversions available
2: Basics
Type conversion
Some automatic type conversions available
from smaller to larger types
Conversions which may lose information require cast
syntax is type name inside parentheses
int i = 5;
double d = 3.2;
d = i;
i = (int)d;
implicit conversion
cast required
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

9. Input Read input using ReadLine from Console class in System namespace
2: Basics
Input
Read input using ReadLine
from Console class in System namespace
returns entire input line as a string
Typically then need to convert string to actual type
conversion methods provided in Convert class
read entire line
string s = System.Console.ReadLine();
int i = System.Convert.ToInt32 (s);
double d = System.Convert.ToDouble(s);
convert string to int
convert string to double
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

10. Output Write output using Write and WriteLine
2: Basics
Output
Write output using Write and WriteLine
from Console class in System namespace
WriteLine adds line terminator in output
overloaded versions allow printing of all types
some versions take format string and data
variable argument list version allows printing multiple values
int i = 3;
double d = 5.2;
System.Console.WriteLine(i);
System.Console.WriteLine(d);
System.Console.WriteLine("first {0} second {1}", i, d);
int
double
multiple
format string
placeholder
value
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

11. Library namespace Core standard library is System namespace
2: Basics
Library namespace
Core standard library is System namespace
a using directive provides shorthand access
using System;
class MyApplication {
static void Main()
string s = Console.ReadLine();
int i = Convert.ToInt32(s);
... }
using directive
short names
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

12. Comments Three comment styles available XML documentation comment ///
2: Basics
Comments
Three comment styles available
XML documentation comment ///
delimited code comment /* ... */
single line code comment //
/// <summary>
/// MyApplication is very simple.</summary>
class MyApplication {
static void Main()
/* delimited comment can extend
across multiple lines */
int x; // comment goes to end of line
... }
documentation
delimited
single line
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

13. Operators Comprehensive set of operators available int x = 5;
2: Basics
Operators
Comprehensive set of operators available
Operator
Description +
addition -
subtraction *
multiplication /
division %
remainder
<<
left shift
>>
right shift
&
bitwise and |
bitwise or ^
bitwise xor ~
bitwise complement
int x = 5;
int y = 3;
int z = x + y;
addition
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

14. Combination assignment
2: Basics
Combination assignment
Several combination assignment operators available
perform both operation and assignment
Operator
Description +=
add / assign -=
subtract / assign *=
multiply / assign /=
divide / assign %=
remainder / assign
<<=
left shift / assign
>>=
right shift / assign
&=
bitwise and / assign |=
bitwise or / assign ^=
bitwise xor / assign
int x = 5;
x += 2;
combination
addition
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

15. Shorthand operators A few shorthand operators available int x = 5;
2: Basics
Shorthand operators
A few shorthand operators available
Operator
Description ++
pre/post increment --
pre/post decrement ?:
conditional
int x = 5;
int y = x++;
int z = ++x;
int x = 5;
int y = 3;
int max;
max = x > y ? x : y;
post-increment
y = 5, x = 6
max set to
greater of
x and y
pre-increment
x = 7, z = 7
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

16. Array Arrays provide efficient storage of multiple data elements
2: Basics
Array
Arrays provide efficient storage of multiple data elements
create using new
specify element type and array size
access elements using operator [ ]
total number of elements recorded in Length property
valid indices are 0 to Length-1
IndexOutOfRangeException generated if index invalid
create
int[] a = new int[5];
a[0] = 17;
a[1] = 32;
int x = a[1];
int l = a.Length;
element access
number of elements
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

17. Array element values Array elements have default values
2: Basics
Array element values
Array elements have default values
0 for numeric types
false for bool
'\x0000' for char
null for references
Programmer can supply initial values
default to false
bool[] a = new bool[10];
int[] b = new int[5];
int[] c = new int[5] { 48, 2, 55, 17, 7 };
default to 0
set to given values
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

18. If statement if statement provides conditional execution
2: Basics
If statement
if statement provides conditional execution
Boolean expression is evaluated
associated statement executed only if expression is true
expression must be inside parentheses
keywords such as "if" are case sensitive
int temperature = 127;
bool boiling = false;
if (temperature >= 100)
boiling = true;
if statement
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

19. If/else statement if statement may provide optional else part
2: Basics
If/else statement
if statement may provide optional else part
executed if expression is false
int x = 3;
int y = 5;
int min;
if (x < y)
min = x;
else
min = y;
else part
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

20. Code block Block required for multiple statements in control construct
2: Basics
Code block
Block required for multiple statements in control construct
use { ... }
int x = 3;
int y = 5;
int min, max;
if (x < y) {
min = x;
max = y; }
else
min = y;
max = x;
block
block
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

21. Comparison and logical operators
2: Basics
Comparison and logical operators
Comparison operators compare two values
yield Boolean result
Combine Boolean values with conditional logical operators
int x;
char c;
if (x > 0 && x < 10)
...
if (c == 'y' || c == 'Y')
if (!Char.IsLetter(c)) ==
equal !=
not equal
<, <=
less
>, >=
greater
&&
and || or !
not
both must be true
either can be true
c can't be a letter
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

22. 2: Basics
Switch statement
switch statement performs selection from a set of options
expression evaluated and matching case executed
case labels must be constant values
end each case with keyword break
optional default case executed if no label matches
double total = 0.0;
char grade = 'C';
switch (grade) {
case 'A': total += 4.0; break;
case 'B': total += 3.0; break;
case 'C': total += 2.0; break;
case 'D': total += 1.0; break;
case 'F': total += 0.0; break;
default: Console.WriteLine("Error"); break; }
switch
cases
default
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

23. Switch type Types allowed in switch are limited integral types string
2: Basics
Switch type
Types allowed in switch are limited
integral types
string
string
string color = "blue";
switch (color) {
case "red" : Console.WriteLine("red"); break;
case "blue" : Console.WriteLine("blue"); break;
case "green": Console.WriteLine("green"); break; }
strings
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

24. 2: Basics
Multiple labels
Can associate several different labels with same action
use separate case for each label
place action in last case
switch (grade) {
case 'A':
case 'B':
case 'C':
Console.WriteLine("pass");
break;
case 'D':
case 'F':
Console.WriteLine("no pass"); }
pass
no pass
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

25. 2: Basics
Multiple actions
Can perform multiple actions for match on single label
must forward control to next desired case
use goto case or goto default instead of break
string level = "gold";
switch (level) {
case "silver":
priorityCheckIn = true;
break;
case "gold":
priorityUpgrade = true;
goto case "silver";
case "platinum":
useOfLounge = true;
goto case "gold"; }
forward control
to other case
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

26. while loop while loop runs as long as condition is true
2: Basics
while loop
while loop runs as long as condition is true
statements repeatedly executed
stops when condition becomes false
int i = 0;
while (i < 5) {
...
i++; }
loop while true
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

27. do-while loop do-while loop test condition located after body
2: Basics
do-while loop
do-while loop test condition located after body
body executed at least once
int x; do {
string s = System.Console.ReadLine();
x = System.Convert.ToInt32(s); }
while (x < 0); do
test done
after body
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

28. for loop for loop centralizes control information
2: Basics
for loop
for loop centralizes control information
initialization, condition, update
parts separated by semicolons
done once at start
loop runs while test is true
done each time after body
for (int k = 0; k < 5; k++) {
... }
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

29. 2: Basics
foreach loop
Specialized foreach loop provided for collections like array
reduces risk of indexing error
provides read only access
int[] data = new int[5] { 48, 2, 55, 17, 7 };
int sum = 0;
foreach (int x in data) {
sum += x; }
foreach
type
value
collection
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

30. Break break statement exits enclosing statement
2: Basics
Break
break statement exits enclosing statement
usable with switch, while, do, for, foreach
int i = 0;
bool error;
while (i < 5) {
...
if (error)
break; }
break
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

31. Continue continue statement skips to end of current loop iteration
2: Basics
Continue
continue statement skips to end of current loop iteration
does not exit loop
usable with while, do, for, foreach
int i = 0;
bool skip;
while (i < 5) {
...
if (skip)
continue; }
continue
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

32. Goto goto transfers control to the specified labeled statement
2: Basics
Goto
goto transfers control to the specified labeled statement
label must be in current or outer scope
label must be in same method
int[,] data = new int[2,4];
for (int i = 0; i < data.GetLength(0); i++) {
for (int j = 0; j < data.GetLength(1); j++)
if (data[i,j] < 0)
goto error;
... }
error:
Console.WriteLine("Error");
goto
label
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003

33. Summary Class is basic unit of C# coding
2: Basics
Summary
Class is basic unit of C# coding
Main defines application entry point
Comprehensive set of types available
Standard operators provided
Arrays provide efficient way to store large amount of data
Control constructs offer balance of convenience and safety
Programming C# © 2003 DevelopMentor, Inc.
12/1/2003