C Sharp Language Basics

Integral Types

DataType	Size	.Net(CTS)	Comments
byte	1	System.Byte	0 - 255 It is Unsigned
sbyte	1	System.SByte	-128 to 127 - Signed
short	2	System.Int16
ushort	2	System.UInt16
int	4	System.Int32
uint	4	System.UInt32
long	8	System.Int64
ulong	8	System.UInt64

 Floating Types

float	4	System.Single	Has up to 8 digits after decimal
double	8	System.Double	Has up to 16 digits after decimal
Deciaml	16	System.Decimal	Has fixed 28 digits after decimal and its fixed

 Other DataTypes

string *	4	Systring.String	Uses Unicode Charset
char	2	Systring.Char	Uses Unicode Charset
bool	1	Systring.Bool
object *		System.Object	Generic Datatype

 Variable Declaration Syntax:

int a,b;

 int a=10, b=20;

·         A local variable declared must be explicitly initialized before used in an expression otherwise gives an compilation error

 using System;

class Program

{

public static void Main()

 {

int n = 256;

 byte b;

unchecked //Overflow checks are not done…

 {

b = (byte) n;

 Console.WriteLine(b);

}

checked //Overflow checks are done…

 {

b = (byte) n;

Console.WriteLine(b);

 }

 double dbl = 0.6D;

//0.6 float f = 0.6F;

decimal dec = 0.6M;

//float and decimal requires casting dec = 10;

 //Integer to decimal //f = dec;

//Invalid //Valid in VB //dec = f;

 //Invalid f = (float) dec;

//In VB-Implicit dec = (decimal) f;

//“decimal” should be explicitly casted to every other type if required.

 string s = "Demo";

char c = 'S';

//In VB - "S"c

 //int to char. n = c;

//In VB: n = AscW(c)

 /*c = n; invalid */

 c = (char) n;

//In VB: c = ChrW(n)

//bool – int /anydatatype explicit or implicit casting is not allowed either direction

//string to int s = "100";

 n = (int) s;

//Invalid – String cannot be casted n = int.Parse(s);

//if failes throws, FormatException bool bln = int.TryParse(s, out n);

//n = (int) s; //Invalid //int to string s = n.ToString();

//s = (string) n //Invalid

//long to float - Same as VB

long lng = 10L;

f = lng;

//because range of long is smaller than float

 lng = (long) f;

object obj = n; //Boxing

n = (int) obj; //Unboxing

 var n = 0

// n is of type

int var s = "Hello"

// s is of type string

const double PI = 3.14;

byte b1, b2, b3;

 b1 = b2 = 10;

//In VB it is not valid b1 = b2 + b3;

//Compilation Error

//if byte, short or char variables are used in an expression they are automatically raised to the rank of int.

 b1 = (byte) (b2 + b3);

Console.WriteLine(3 / 2); //Result - 1

                Console.WriteLine(3.0 / 2); //Result - 1.5

n = 10;

int m = n++;

//m=n; n=n+1 - Post Increment

Console.WriteLine(n + " " + m);

m = ++n; //n=n+1; m=n - Pre Increment

Console.WriteLine(n + " " + m);

//?: Conditional Operator (VB: IIf)

int max;

max = n > m ? n : m; //?: Operator

           //Enum Sample

n = 2; //n is int

WeekDay wd = WeekDay.Sat;

wd = (WeekDay) n;

                //Explicit

                //n = wd;

                //Invalid n = (int) wd;

//Explicit - In VB.NET it‟s not required

 }

 }

enum WeekDay : int //WeekDay is subtype of int

 {

Sun=1, Mon, Tues, Wed=5, Thus, Fri, Sat

 }

Enum can be subtype of any integral type only

OverflowException.

Operators Arithmetic	+, -, * , / , % (mod) (Power operator is missing)
Logical Operators	^ (XOR), !(NOT) && (VB-AndAlso) , || (VB-OrElse)
Ternary Operator	?:
String concatenation	+ (VB-&)
Increment, decrement	++ , --
Bitwise	<< , >>, & , | , ~ (complement/negation)
Relational	= = , != , < , > , <= , >=
Assignment	= , += , -= , *= , /= , %= , &= , | = , ^= , <<= , >>=
Type information	is , sizeof , typeof, as
Indirection and Address	* , -> , [] , &

Note for VB.NET Programmers:

In C# the arithmetic operator „/ ‟ is the same for both floating point and integer datatypes and the result depends on the operands.

Control Statements

if-statement: if (BooleanExpression) { statement; } else if (Boolean-Expression) { statement; } else { statement; }	Switch Statement int expr; switch (expr) //expr can only integral type / char / string { case 0: //value of case must be a constant. statements; goto default; // or break can be used. case 1: case 2: statements; break; //break must be preset after every case with statements default: statements; break; //break must be present after default also. }
while…..loop while (BooleanExpression) { Statements; }	do { Statements; }while (BooleanExpression);

for and foreach statements for ( initializer; condition; iterator ) { statements; } foreach (DataType identifier in <Array or Collection>) { embedded-statements; }  for (int i = 0; i < 10; i++)  { if (i == 7) break;  if (i == 3) continue;  Console.WriteLine(i); }  foreach (string s in args) Console.WriteLine(s);

class Program { static void Main(string[] args) { for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { if (i == j) break; Console.WriteLine(i + " " + j); } } } }

·         “break” and “continue” statements can be used in “for” and “while” loops.

·         C# doesn‟t support “With” statement

Working with Arrays

1.       Single-Dimensional Arrays

int [] myArray = new int [5];

string []myStringArray = new string[5];

 When you initialize an array upon declaration, it is possible to use the following shortcuts:

 int[] myArray = {1, 3, 5, 7, 9};

string[] weekDays = {"Sun", "Sat", "Mon", "Tue"};

It is possible to declare an array variable without initialization, but you must use the new operator when you assign an array to this variable.

For example: int[] myArray;

 myArray = new int[] {1, 3, 5, 7, 9}; // OK

 myArray = {1, 3, 5, 7, 9}; // Error

 weekdays = new string[] {“Sunday”, “Monday”, “Tuesday”};

2. Multidimensional Arrays

int[,] myArray = new int[4,2];

Also, the following declaration creates an array of three dimensions, 4, 2, and 3:

int[,,] myArray = new int [4,2,3];

You can initialize the array upon declaration as shown in the following example:

 int[,] myArray = new int[,] {{1,2}, {3,4}, {5,6}, {7,8}};

You can also initialize the array without specifying the rank:

 int[,] myArray = {{1,2}, {3,4}, {5,6}, {7,8}};

 If you choose to declare an array variable without initialization, you must use the new operator to assign an array to the variable. For example:

int[,] myArray; myArray = new int[,] {{1,2}, {3,4}, {5,6}, {7,8}}; // OK

 myArray = {{1,2}, {3,4}, {5,6}, {7,8}}; // Error

class Program

 {

static void Main(string[] args)

{

 int[] ar = new int[ ] {1,2,3,4};

 Console.WriteLine(ar.Length);

Console.WriteLine(ar.Rank); //Prints Number of Dimensions in array.

 foreach (int n in ar)

Console.WriteLine(n); //To increase the size of existing array and also retaining data in it. i.e equivalent of Redim Preserve in VB.

 int[] temp =ar;

ar = new int[temp.Length +1];

 Array.Copy(temp, ar, temp.Length);

temp=null;

foreach (int n in ar)

Console.WriteLine(n);

}

 }

 Working with Methods

using System;  class Program2 { public static void Main()  {  int res = Add(10, 2);  int[] mar = { 1, 2, 3, 4 };  res = Add(mar); res = Add();  res = Add(1, 2, 3, 4, 5);  res = Add(1, 2, 3, 4, 5, 6);  res = Add(1, 2, 3, 4, 5, 6, 7); //Pass by value or reference example…. int n1, n2, n3; n1 = n3 = 10; Foo(n1, out n2, ref n3); Console.WriteLine(n1 + " " + n2 + " " + n3); }  //Pass by value and reference example static void Foo(int a, out int b, ref int c) {  a++; b = 20; c++;  }

static int Add(int a, int b)  { return Add(a, b, 0); } static int Add(int a, int b, int c) { return a + b + c; } static string Add(string s1, string s2) { return s1 + s2; } static int Add(params int[] ar) { int sum = 0; foreach (int n in ar) sum += n; return sum; } }

·         Out parameter must be initialized in the method and are generally used in situations where we want to return more than one value from the method.

·         C# doesn’t support Optional parameters with default values and Named arguments.

static int Foo(int a) { if (a != 0) return a; }

If a method has return type anything other than “void”, all code paths in it must return a value. The example gives compilation error because if a==0 nothing is mentioned as return value.

General Points; For String: @"C:\Demo" or "C:\\Demo", "This is \"Quoted\" String"