Introduction to c#

Why C# ?
• Builds on COM+ experience
• Native support for
– Namespaces
– Versioning
– Attribute-driven development
• Power of C with ease of Microsoft Visual Basic®
• Minimal learning curve for everybody
• Much cleaner than C++
• More structured than Visual Basic
• More powerful than Java

C# – The Big Ideas
A component oriented language
• The first “component oriented” language in
the C/C++ family
– In OOP a component is: A reusable program that can be
combined with other components in the same system to form
an application.
– Example: a single button in a graphical user interface, a small
interest calculator
– They can be deployed on different servers and communicate
with each other

• Enables one-stop programming
– No header files, IDL, etc.
– Can be embedded in web pages

C# Overview
• Object oriented
• Everything belongs to a class
– no global scope
• Complete C# program:
using System;
namespace ConsoleTest
{
class Class1
{
static void Main(string[] args)
{
}
}
}

C# Program Structure
• Namespaces
– Contain types and other namespaces
• Type declarations
– Classes, structs, interfaces, enums,
and delegates
• Members
– Constants, fields, methods, properties, events, operators,
constructors, destructors
• Organization
– No header files, code written “in-line”
– No declaration order dependence

Simple Types
• Integer Types
– byte, sbyte (8bit), short, ushort (16bit)
– int, uint (32bit), long, ulong (64bit)

• Floating Point Types
– float (precision of 7 digits)
– double (precision of 15–16 digits)

• Exact Numeric Type
– decimal (28 significant digits)

• Character Types
– char (single character)
– string (rich functionality, by-reference type)

• Boolean Type
– bool (distinct type, not interchangeable with int)

Arrays
• Zero based, type bound
• Built on .NET System.Array class
• Declared with type and shape, but no bounds
– int [ ] SingleDim;
– int [ , ] TwoDim;
– int [ ][ ] Jagged;
• Created using new with bounds or initializers
– SingleDim = new int[20];
– TwoDim = new int[,]{{1,2,3},{4,5,6}};
– Jagged = new int[1][ ];
Jagged[0] = new int[ ]{1,2,3};

Statements and Comments

• Case sensitive (myVar != MyVar)
• Statement delimiter is semicolon ;
• Block delimiter is curly brackets { }
• Single line comment is //
• Block comment is /* */
– Save block comments for debugging!

Data
• All data types derived from
System.Object
• Declarations:
datatype varname;
datatype varname = initvalue;
• C# does not automatically initialize local
variables (but will warn you)!

Value Data Types
• Directly contain their data:
– int (numbers)
– long (really big numbers)
– bool (true or false)
– char (unicode characters)
– float (7-digit floating point numbers)
– string (multiple characters together)

Data Manipulation

= assignment
+ addition
- subtraction
* multiplication
/ division
% modulus
++ increment by one
-- decrement by one

strings
• Immutable sequence of Unicode characters
(char)

• Creation:
– string s = “Bob”;
– string s = new String(“Bob”);

• Backslash is an escape:
– Newline: “n”
– Tab: “t”

string/int conversions
• string to numbers:
– int i = int.Parse(“12345”);
– float f = float.Parse(“123.45”);

• Numbers to strings:
– string msg = “Your number is ” + 123;
– string msg = “It costs ” +
string.Format(“{0:C}”, 1.23);

String Example
using System;
{
class Class1
{
static void Main(string[ ] args)
{
int myInt;
string myStr = "2";
bool myCondition = true;

Console.WriteLine("Before: myStr = " + myStr);
myInt = int.Parse(myStr);
myInt++;
myStr = String.Format("{0}", myInt);
Console.WriteLine("After: myStr = " + myStr);

while(myCondition) ;
}
}
}

Arrays
• (page 21 of quickstart handout)
• Derived from System.Array
• Use square brackets []
• Zero-based
• Static size
• Initialization:
– int [ ] nums;
– int [ ] nums = new int[3]; // 3 items
– int [ ] nums = new int[ ] {10, 20, 30};

Arrays Continued
• Use Length for # of items in array:
– nums.Length
• Static Array methods:
– Sort System.Array.Sort(myArray);
– Reverse System.Array.Reverse(myArray);
– IndexOf
– LastIndexOf
Int myLength = myArray.Length;
System.Array.IndexOf(myArray, “K”, 0, myLength)

Arrays Final
• Multidimensional

// 3 rows, 2 columns
int [ , ] myMultiIntArray = new int[3,2]

for(int r=0; r<3; r++)
{
myMultiIntArray[r][0] = 0;
myMultiIntArray[r][1] = 0;
}

Conditional Operators

== equals
!= not equals

< less than
<= less than or equal
> greater than
>= greater than or equal

&& and
|| or

If, Case Statements

if (expression) switch (i) {
case 1:
{ statements; }
statements;
else if break;
case 2:
{ statements; }
statements;
else break;
default:
{ statements; } statements;
break;
}

Loops

for (initialize-statement; condition; increment-statement);
{
statements;
}

while (condition)
{
statements;
}

Note: can include break and continue statements

Classes, Members and Methods
• Everything is encapsulated in a class
• Can have:
– member data
– member methods

Class clsName
{
modifier dataType varName;
modifier returnType methodName (params)
{
statements;
return returnVal;
}
}

Class Constructors
• Automatically called when an object is
instantiated:

public className(parameters)
{
statements;
}

Hello World

namespace Sample
{
using System;

public class HelloWorld
Constructor
{
public HelloWorld()
{
}

public static int Main(string[]
args)
{
Console.WriteLine("Hello
World!");
return 0;
}
}

Another Example
using System;
{
public class Class1
{
public string FirstName = "Kay";
public string LastName = "Connelly";

public string GetWholeName()
{
return FirstName + " " + LastName;
}

static void Main(string[] args)
{
Class1 myClassInstance = new Class1();

Console.WriteLine("Name: " + myClassInstance.GetWholeName());

while(true) ;
}
}
}

Summary
• C# builds on the .NET Framework
component model
• New language with familiar structure
– Easy to adopt for developers of C, C++, Java,
and Visual Basic applications
• Fully object oriented
• Optimized for the .NET Framework

ASP .Net and C#
• Easily combined and ready to be used in
WebPages.
• Powerful
• Fast
• Most of the works are done without
getting stuck in low level programming and
driver fixing and …

Introduction to c#

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