DITEC - Programming with C#.NET

Diploma in Information Technology
Module IX: Programming with
C#.NET
Rasan Samarasinghe
ESOFT Computer Studies (pvt) Ltd.
No 68/1, Main Street, Pallegama, Embilipitiya.

Contents
1. Introduction to .NET Framework
2. .NET Framework Platform Architecture
3. Microsoft Visual Studio
4. C# Language
5. C#, VS and .NET Framework Versions
6. Your First C# Application
7. Printing Statements
8. Comments in C#
9. Common Type System
10. Value Types and Reference Type
11. Variables Declaration in C#
12. Type Conversion
13. Arithmetic Operators
14. Assignment Operators
15. Comparison Operators
16. Logical Operators
17. If Statement
18. If… Else Statement
19. If… Else if… Else Statement
20. Nested If Statement
21. Switch Statement
22. While Loop
23. Do While Loop
23. For Loop
24. Arrays
25. Accessing Arrays using foreach Loop
26. Two Dimensional Arrays
27. Classes and Objects in C#
28. Inheritance in C#
29. Partial Classes
30. Namespaces
31. Windows Forms Applications
32. Using Buttons, Labels and Text Boxes
33. Displaying Message Boxes
34. Error Handling with Try… Catch… finally…
35. Using Radio Buttons
36. Using Check Boxes
37. Using List Boxes
38. Creating Menus
39. Creating ToolStrips
40. MDI Forms
41. Database Application in C#
42. Creating a Simple Database Application
43. SQL Insert / Update / Retrieving / Delete
44. SQL Command Execute Methods
45. Data Sets

Introduction to .NET Framework
• The .NET Framework is a software
framework developed by Microsoft
that runs primarily on Microsoft
Windows.
• It includes a large library and provides
language interoperability across
several programming languages.
• Programs written for .NET Framework
execute in a software environment
known as CLR.
• .NET Framework is intended to be
used by most new applications
created for the Windows platform.

.NET Framework Platform Architecture

Microsoft Visual Studio
• Microsoft Visual Studio is an integrated development
environment (IDE) from Microsoft…
• To develop Windows Forms or WPF applications, web
sites, web applications, and web services…
• For Microsoft Windows, Windows Mobile, Windows
CE, .NET Framework and Microsoft Silverlight.

C# Language
C# is a general purpose, object oriented
programming language developed by Microsoft
within its .NET initiative led by Anders Hejlsberg.

C# Language Features
• Boolean Conditions
• Automatic Garbage Collection
• Standard Library
• Assembly Versioning
• Properties and Events
• Delegates and Events Management
• Easy-to-use Generics
• Indexers
• Conditional Compilation
• Simple Multithreading
• LINQ and Lambda Expressions
• Integration with Windows

C#, VS and .NET Framework Versions
C# Version Visual Studio Version .NET Framework Version
C# 1.0 Visual Studio .NET 2002 .NET Framework 1.0
C# 1.2 Visual Studio .NET 2003 .NET Framework 1.1
C# 2.0 Visual Studio 2005 .NET Framework 2.0
C# 3.0
Visual Studio 2008
Visual Studio 2010
.NET Framework 2.0
.NET Framework 3.0
.NET Framework 3.5
C# 4.0 Visual Studio 2010 .NET Framework 4
C# 5.0
Visual Studio 2012
Visual Studio 2013
.NET Framework 4.5

Your First C# Application
using System;
namespace myspace
{
class FirstApp
{
static void Main()
{
Console.WriteLine(“Hello World!”);
}
}
}

Printing Statements
Console.Write(“Hello World!”); //prints a text
Console.WriteLine(“Hello World!”); //prints text and
starts a new line
Console.Write(“Hello nWorld!”); //line breaks
Console.Write(“Hello {0}”, “Esoft”); //variable
displaying

Comments in C#
Single line comments
// this is a single line comment
Multiline comments
/*
this is
a multiline
comment
*/

Value Types and Reference Type
Predefined Value Types
sbyte -128 to 127 8 bits
byte 0 to 255 8 bits
short -32,768 to 32,767 16 bits
ushort 0 to 65,535 16 bits
int -2,147,483,648 to 2,147,483,647 32 bits
uint 0 to 4,294,967,295 32 bits
long -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 64 bits
ulong 0 to 18,446,744,073,709,551,615 64 bits
char 16 bit Unicode character 16 bits
float -3.4 x 1038 to + 3.4 x 1038 32 bits
double (+/-)5.0 x 10-324 to (+/-) 1.7 x 10308 64 bits
decimal (-7.9 x 1028 to 7.9 x 1028) / 100 to 28 128 bits
bool Holds true or false 1 bit
Predefined Reference Types
string Represents a string of Unicode characters 20+ bits
object Represents a general purpose type 8+ bits

Variable Declaration in C#
Variable declaration
type variable_list;
Variable declaration and initialization
type variable_name = value;

Variable Declaration in C#
int a, b, c; // declares three ints, a, b, and c.
int d = 3, e, f = 5; // declares three more ints,
initializing d and f.
bool z = 5>2; // declares and initializes z.
double pi = 3.14159; // declares an approximation
of pi.
char x = 'x'; // the variable x has the value 'x'.

Type Conversion
• Implicit Conversion
– No special syntax is required because the
conversion is type safe and no data will be lost.
• Explicit Conversion
– Require a cast operator, and information might be
lost in the conversion.
• Conversions with helper classes
– To convert between non-compatible types.

Implicit Conversion
int x = 123;
double y = x;

Explicit Conversion
double y = 123.5;
int x = (int)y;

Conversions with helper classes
String x = "123";
int y = Int.Parse(x);
int z = Convert.ToInt32(x);

Arithmetic Operators
Operator Description Example
+ Addition X + Y will give 60
- Subtraction X - Y will give -20
* Multiplication X * Y will give 800
/ Division Y / X will give 2
% Modulus Y % X will give 0
++ Increment Y++ gives 41
-- Decrement Y-- gives 39
X = 20, Y = 40

Assignment Operators
Operator Example
= Z = X + Y will assign value of X + Y into Z
+= Z += X is equivalent to Z = Z + X
-= Z -= X is equivalent to Z = Z - X
*= Z *= X is equivalent to Z = Z * X
/= Z /= X is equivalent to Z = Z / X
%= Z %= X is equivalent to Z = Z % X

Comparison Operators
Operator Example
== (X == Y) is false.
!= (X != Y) is true.
> (X > Y) is false.
< (X < Y) is true.
>= (X >= Y) is false.
<= (X <= Y) is true.
X = 50, Y = 70

Logical Operators
Operator Name Example
&& AND (X && Y) is False
|| OR (X || Y) is True
! NOT !(X && Y) is True
X = True, Y = False

If Statement
if(Boolean_expression)
{
// Statements will execute if the
Boolean expression is true
}
Boolean
Expression
Statements
True
False

If… Else Statement
if(Boolean_expression)
{
// Executes when the Boolean expression is
true
}
else
{
// Executes when the Boolean
expression is false
}
Boolean
Expression
Statements
True
False
Statements

If… Else if… Else Statement
if(Boolean_expression 1)
{
// Executes when the Boolean expression 1 is true
}
else if(Boolean_expression 2)
{
}
else if(Boolean_expression 3)
{
}
else
{
// Executes when the none of the above condition is true.
}

If… Else if… Else Statement
Boolean
expression 1
False
Statements
Boolean
expression 2
Boolean
expression 3
Statements
Statements
False
False
Statements
True
True
True

Nested If Statement
{
// Executes when the Boolean expression 1 is
true
{
// Executes when the Boolean expression 2 is
true
}
}
Boolean
Expression 1
True
False
Statements
Boolean
Expression 2
True
False

Switch Statement
switch (value)
{
case constant:
// statements
break;
case constant:
// statements
break;
default:
// statements
break;
}

While Loop
while(Boolean_expression)
{
// Statements
}
Boolean
Expression
Statements
True
False

Do While Loop
do
{
// Statements
}while(Boolean_expression);
Boolean
Expression
Statements
True
False

For Loop
for(initialization; Boolean_expression; update)
{
// Statements
}
Boolean
Expression
Statements
True
False
Update
Initialization

Arrays
10 30 20 50 15 35
0 1 2 3 4 5
Size = 6
Element Index No
An Array can hold many values in a same
data type under a single name
A single dimensional array

Building a Single Dimensional Array
// creating an Array
DataType[] ArrayName = new DataType[size];
// assigning values
ArrayName[index] = value;
ArrayName[index] = value;
……..

char[] letters = new char[4];
letters[0] = ‘O’;
letters[1] = ‘P’;
letters[2] = ‘Q’;
letters[3] = ‘R’;
0 1 2 3
O P Q R
0 1 2 3
letters
letters
Values in an Array can access
by referring index number

// creating an array using array initializer
DataType[] ArrayName = {element 1, element 2,
element 3, … element n};
int[] marks = {10, 20, 30, 40, 50}; 10 20 30 40
0 1 2 3
intArr
50
4

Accessing Arrays using foreach Loop
// creating an Array
int[] marks = {10, 29, 30, 40, 50, 70};
// accessing array elements
foreach(int n in marks)
{
System.Console.WriteLine(n);
}

Two Dimensional Arrays
5 10 15
25 50 75
0 1 2
0
1
int[,] myMatrix = new int[2,3];
myMatrix[0,0] = 5;
myMatrix[0,1] = 10;
myMatrix[0,2] = 15;
myMatrix[1,0] = 25;
myMatrix[1,1] = 50;
myMatrix[1,2] = 75;
Rows Columns
Column Index
Row Index

Two Dimensional Arrays
Using array initializer…
int[,] myMatrix = new int[2,3] {{5,10,15},{25,50,75}};
int[,] myMatrix = {{5,10,15},{25,50,75}};
Or

Classes and Objects in C#
Method
Student
name
age
Register()
class Student
{
public String name;
public int age;
public Student(){
}
public void Register(){
Console.WriteLine(“Registered!”);
}
}
Attributes
Constructor

C# Objects
Student st = new Student(); //creating an object
//Assigning values to Attributes
st.name = “Roshan”;
st.age = 20;
//calling method
st.Register();

Inheritance in C#
class Animal
{
//attributes and methods
}
class Lion : Animal
{
}
class Cat : Animal
{
}
Animal
Lion Cat

Partial Classes
partial class Student
{
public int age;
}
{
public String name;
}
{
public String address;
public void Register(){
Console.Write("Student Registered");
}
}
Partials of the same class

Namespaces
• Namespace is an
organization construct.
• It’s a group of collected
types.
• It’s helping to
understand how the
code base is arranged.
• Namespaces are not
essential for C#
programs.
namespace esoft
{
class ditec{
}
class dise{
}
}

Importing Namespaces
Importing Namespace by using “using” directive
using System.Linq;
Importing Namespace with alias directive
using ns = System.Linq;
Direct accessing Namespaces
System.Console.WriteLine(“hello”);

Windows Forms Applications
• A Windows Forms application is an event-
driven application supported by Microsoft's
.NET Framework.
• This model provides object-oriented,
extensible set of classes that enable you to
develop rich Windows applications.

Using Button, Labels and Text Boxes
private void button1_Click(object sender, EventArgs e)
{
label2.Text = "Welcome " + textBox1.Text;
}

Displaying Message Boxes
MessageBox.Show("Hello World","MessageBox Demo",MessageBoxButtons.YesNo,
MessageBoxIcon.Information);
MessageBox.Show("Hello World“);

Error Handling with Try… Catch… finally…
try
{
//Protected code
}
catch (Exception ex)
{
//Catch block
}
finally
{
//The finally block always executes
}

Using Radio Buttons
{
if (radioButton1.Checked)
{
MessageBox.Show("You have chosen Black");
}
else
{
MessageBox.Show("You have chosen White");
}
}

Using Check Boxes
{
if (checkBox1.Checked)
{
MessageBox.Show("You have accepted Terms of Agreement");
}
else
{
MessageBox.Show("You haven't accepted Terms of Agreement");
}
}

Using List Boxes
Statements for each button click events
listBox1.Items.Add(textBox1.Text);
listBox1.Items.AddRange(new String[] {
“America", “Japan", “India" });
listBox1.Items.Insert(0, textBox1.Text);
listBox1.Items.Remove(listBox1.SelectedItem);
listBox1.Items.RemoveAt(int.Parse(textBox1.Text
));
listBox1.Items.Clear();
listBox1.Sorted = true;

Creating Menus
private void newToolStripMenuItem_Click(object sender, EventArgs e)
{
MessageBox.Show("You have clicked New Menu item!");
}

Creating ToolStrips
private void newToolStripButton_Click(object sender, EventArgs e)
{
MessageBox.Show("You have clicked newToolStripButton!");
}

MDI Forms
private void document1ToolStripMenuItem_Click(object sender, EventArgs e)
{
Document_One form1 = new Document_One();
form1.MdiParent = this;
form1.Show();
}

Database Application in C#
Application DataBase
Insert, Update, Retrieving
and Delete Processes

Creating a Simple Database Application
Creating a simple database application involved with
following steps.
1. Import the namespaces
2. Creating a SQL Connection
3. Open SQL Connection
4. Create a SQL Command
5. Execute the SQL Command
6. Extract data from SQL Data Reader
7. Clean up the environment

Creating a Simple Database Application
using System;
using System.Data.SqlClient;
class Program
{
static void Main(string[] args)
{
SqlConnection con = new SqlConnection("Data Source=.SQLEXPRESS; Initial Catalog=esoftdb;
Integrated Security=yes");
con.Open();
SqlCommand cmd = new SqlCommand("SELECT * FROM tblStudent", con);
SqlDataReader rd = cmd.ExecuteReader();
while (rd.Read())
{
Console.Write(rd["id"].ToString() + " ");
Console.Write(rd["name"].ToString() + " ");
Console.WriteLine(rd["address"].ToString());
}
rd.Close();
con.Close();
Console.ReadLine();
}
}
1
2
3
4
5
6
7

SQL Insert / Update / Retrieving / Delete
Inserting Data into Database
SqlCommand cmd = new SqlCommand(“INSERT tblStudent VALUES(1, ‘Roshan’,
‘Colombo’)", con);
Updating Data in Database
SqlCommand cmd = new SqlCommand(“UPDATE tblStudent SET address=‘kandy’
WHERE id=1", con);
Retrieving Data from Database
Deleting Data in Database
SqlCommand cmd = new SqlCommand(“DELETE FROM tblStudent WHERE id=1",
con);

SQL Command Execute Methods
• ExecuteNonQuery() : Executes a Transact-SQL statement against
the connection and returns the number of rows affected.
• ExecuteReader() : Sends the CommandText to the Connection and
builds a SqlDataReader.
• ExecuteScalar() : Executes the query, and returns the first column of
the first row in the result set returned by the query.
int n = cmd.ExecuteNonQuery();
SqlDataReader rd = cmd.ExecuteReader();
String name= cmd.ExecuteScalar();

Data Sets
Represents an in-memory cache of data.
SqlConnection con = new SqlConnection("Data Source=.SQLEXPRESS; Initial
Catalog=esoftdb; Integrated Security=yes");
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds, “tblStudent”);

The End
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DITEC - Programming with C#.NET

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