A Hacker’s Approach to C#

J.D. Melvin

Vision Implementers, Inc.

C# Environment

Program in C# (or VB.NET or C++)

Build project (called a Solution, which can contain one or more assemblies)

Compile each assembly into IL (intermediate language)

Run solution under CLR (common run time) which

Checks IL to make sure it is well behaved

Combines assemblies in a solution to make a single executable

Converts IL of all assembiles to machine code optimized for machine on which it is running

Common Run Time

Completely object oriented

Every program and/or procedure is a method

Every variable is a class with value and useful methods like ToString (convert value to a string)

IL implements classes and objects so all .NET languages can share objects, methods, values

Uses a CTS (common type system) – common variable types for all .NET languages

The C# Program

using System;

namespace ConsoleApplication2

{class Class1{static void Main(string[] args) {

int i;long result,ticks; double seconds; const long limit=100000000;

result=0;ticks=DateTime.Now.Ticks;

Console.WriteLine("Start");

for (i=1;i<=100000000;i++) result=result+i;

seconds=(DateTime.Now.Ticks-ticks)/10000000.0;

Console.WriteLine("End"+

"\n"+seconds.ToString()+

" seconds for sum from 1 to "+(object)limit.ToString()+

"\nSum = "+result.ToString()+

"\nEuler forumula n(n+1)/2 = "+(limit*(limit+1)/2).ToString());}

}

}

Features of the Program

.NET base classes – many of them, for math, database access, windows applications, web applications, etc, etc

Namespaces – named heirarchically; all under System (e.g., Now gives current date and time; it is in System.DateTime.)

Main method always runs first.

Variables are strongly typed: Given one type in a declaration and keep that type (e.g. ticks [long] must be separate from result [double])

Basic C# Syntax

/* … */ and //… specify that … are comments

C# is case-sensitive (for keywords and variables)

Statements end with ; (semi-colon) and can be continued on subsequent lines without a continuation character

using XYZ; specifies that XYZ is the default namespace for referenced classes (subnamespaces can be specified; e.g., after using System, referencing DateTime.Now is equivalent to referencing System.DateTime.Now)

namespace ABC {….} specifies that …. are classes in namespace ABC

class PQR {…} says that … are the properties and methods of class PQR

Declaration of Fields

Declarations of fields (variables) have form ([…] means OPTIONAL)

[<modifier(s)>] <type> <name> [= <value>];

<modifier(s)> and <type> are described below, <name> is the variable name, and the optional <value> is its initial value; variables used before

being assigned a value here or in the code cause an error.

[<attribute>] can precede method declaration (use the square brackets here!)

Declaration of Methods

[<modifier(s)>] <type> <name> ([parameters]) {…}

declares a method (here […] means optional, as usual)

{…} is the method code, <modifiers> and <type> are of the return value when method is a function, <name> is the method name

Any group of statements {…} are one or more statements, each ending with ;

Attributes and Modifiers

Modifers for variables: public (accessible anywhere); internal (in current program only); protected (in current class or subclasses); protected internal (protected or internal); private (in current class only)

Modifiers for declaring fields (non-local variables): internal (in current program only), new (new instance of an object); private (in current class only); protected (in current class or subclasses); readonly (cannot be changed after first initialization); static (methods can be called on the base class – an instance does not have to be created)

CTS (common type system)

Type

Reference Type

Built-in (object, string – written as ”XYZABC”)

Interface Types (method parameter/return templates)

Pointer Types (addresses of values)

Self-describing Types

Arrays (lists of objects of given type(s))

Class Types

Delegates (pointers to methods)

Boxes Values (objects representing values)

User-defined Reference Types

CTS - continued

Value Type

Built-in Type

Integer types (sbyte, short, int, long, byte,

ushort, uint, ulong)

Floating point types (float, double, decimal

[128 bit])

Boolean (bool [T/F])

Character (char [single character – values

written ’x’])

User-defined Type

Enumeration (named integer values)

Complex Types

Complex Type

Structure

struc Name {string First; string Last};

Name Jon, New; Jon.First=“Jon”; Jon.Last=“Melvin”; Name NewName;

Array (subscripts are always surrounded with […]; subscripts go from 0, …)

int[] Integers=new Int[32]; /* declare array Integers of 32 integers */

/* create and initialize array of 3 string answers */

string[] Answers=new string[] {“Yes”,”No”,”Maybe”}

/* this fails; only constant length arrays allowed; Answer[0]=“Yes” */

int a=5; int[] Array=new int[a];

/* 2 dimensional arrays */

string[][] Names=new string[2][];

Names[0]=new string[]{"James","Joyce"};

Names[1]=new string[3]{"E","B","White"}; /* Name[1,2]=‘White’ */

Fields of given type are objects. Some methods are of object instance, some of base

class. E.g., int i=5; string s=i.ToString; int[] Test int[](1,3,2); Array.Reverse(Test)

changes order of elements to 2,3,1.

Array.Sort(Test) changes order to 1,2,3.

Array Example

using System;

namespace ConsoleApplication2

{class Class1{static void Main(string[] args) {

string[][] Names=new string[2][];

Names[0]=new string[]{"James","Joyce"};

Names[1]=new string[3]{"E","B","White"};

Console.WriteLine(Names[1][2]);

}}}

Complex Types - continued

Enumeration

public enum TimeOfDay {Morning=0,Afternoon=1,Evening=2};

Enum Example:

using System;

namespace vi.Examples.Enum{

enum TimeOfDay{Morning=1,Afternoon=2,Evening=3};

class Class1{ static void Main(string[] args) {

TimeOfDay Time;

Time=TimeOfDay.Morning;

Console.WriteLine(Greeting(Time));}

static string Greeting(TimeOfDay Time) {

switch(Time){

case TimeOfDay.Morning: return "Good Morning";

case TimeOfDay.Afternoon: return "Good Afternoon";

case TimeOfDay.Evening: return "Good Evening";

default: return "Hello";}}}}

A Database Program Example

using System; using System.Data;

namespace Table

{class Class1{static void Main() {

int i;

DataSet ds=new DataSet();

DataTable test=new DataTable("Test");

test.Columns.Add(new DataColumn("test",typeof(int)));

ds.Tables.Add(test);

       for (i=1;i<1000;i++) {DataRow r=ds.Tables["Test"].NewRow();

          r["test"]=i; ds.Tables["Test"].Rows.Add(r);};

       foreach(DataRow theRow in ds.Tables["Test"].Rows) {Console.WriteLine(theRow["test"]);};

}

}}

A Windows Program Example

using System;

using System.Drawing;

using System.Collections;

using System.ComponentModel;

using System.Windows.Forms;

using System.Data;

namespace WindowsApplication1 {public class Form1 : System.Windows.Forms.Form {

private System.Windows.Forms.Button button1;

private System.Windows.Forms.Label label1;

private System.ComponentModel.Container components = null;

public Form1(string args) {InitializeComponent(args);}

protected override void Dispose( bool disposing ) {

if(disposing) if(components != null) components.Dispose();

base.Dispose( disposing );}

private void InitializeComponent(string args) { this.button1 = new

Windows Example - continued

System.Windows.Forms.Button();

this.label1 = new System.Windows.Forms.Label();

this.SuspendLayout();

this.button1.Location = new System.Drawing.Point(109, 208);

this.button1.Name = "button1"; this.button1.TabIndex = 0; this.button1.Text = "Exit";

this.button1.Click += new System.EventHandler(this.button1_Click);

this.label1.Location = new System.Drawing.Point(70, 56);

this.label1.Name = "label1"; this.label1.TabIndex = 1; this.label1.Text = args;

this.label1.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;

this.label1.Size = new System.Drawing.Size(152, 23);

this.Name = "Form1"; this.Text = "Sample Form";

this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);

this.ClientSize = new System.Drawing.Size(292, 270);

this.Controls.AddRange(new System.Windows.Forms.Control[] {this.label1,this.button1});

this.ResumeLayout(false);}

[STAThread] static void Main(string[] args) {Application.Run(new Form1(args[0]));}

private void button1_Click(object sender, System.EventArgs e) {this.Close() ;}

}}


	Program in C# (or VB.NET or C++)
	Build project (called a Solution, which can contain one or more assemblies)
	Compile each assembly into IL (intermediate language)
	Run solution under CLR (common run time) which
		Checks IL to make sure it is well behaved
		Combines assemblies in a solution to make a single executable
		Converts IL of all assembiles to machine code optimized for machine on which it is running


	Completely object oriented
		Every program and/or procedure is a method
		Every variable is a class with value and useful methods like ToString (convert value to a string)
		IL implements classes and objects so all .NET languages can share objects, methods, values
	Uses a CTS (common type system) – common variable types for all .NET languages


	using System;
	namespace ConsoleApplication2
	{class Class1{static void Main(string[] args) {
	int i;long result,ticks; double seconds; const long limit=100000000;
	result=0;ticks=DateTime.Now.Ticks;
	Console.WriteLine("Start");
	for (i=1;i<=100000000;i++) result=result+i;
	seconds=(DateTime.Now.Ticks-ticks)/10000000.0;
	Console.WriteLine("End"+
	"\n"+seconds.ToString()+
	" seconds for sum from 1 to "+(object)limit.ToString()+
	"\nSum = "+result.ToString()+
	"\nEuler forumula n(n+1)/2 = "+(limit*(limit+1)/2).ToString());}
	}
	}


	.NET base classes – many of them, for math, database access, windows applications, web applications, etc, etc
	Namespaces – named heirarchically; all under System (e.g., Now gives current date and time; it is in System.DateTime.)
	Main method always runs first.
	Variables are strongly typed: Given one type in a declaration and keep that type (e.g. ticks [long] must be separate from result [double])


	/* … */ and //… specify that … are comments
	C# is case-sensitive (for keywords and variables)
	Statements end with ; (semi-colon) and can be continued on subsequent lines without a continuation character
	using XYZ; specifies that XYZ is the default namespace for referenced classes (subnamespaces can be specified; e.g., after using System, referencing DateTime.Now is equivalent to referencing System.DateTime.Now)
	namespace ABC {….} specifies that …. are classes in namespace ABC
	class PQR {…} says that … are the properties and methods of class PQR


	Declarations of fields (variables) have form ([…] means OPTIONAL)
	[<modifier(s)>] <type> <name> [= <value>];
	<modifier(s)> and <type> are described below, <name> is the variable name, and the optional <value> is its initial value; variables used before
	being assigned a value here or in the code cause an error.

	[<attribute>] can precede method declaration (use the square brackets here!)


	[<modifier(s)>] <type> <name> ([parameters]) {…}
	declares a method (here […] means optional, as usual)
	{…} is the method code, <modifiers> and <type> are of the return value when method is a function, <name> is the method name

	Any group of statements {…} are one or more statements, each ending with ;


	Modifers for variables: public (accessible anywhere); internal (in current program only); protected (in current class or subclasses); protected internal (protected or internal); private (in current class only)

	Modifiers for declaring fields (non-local variables): internal (in current program only), new (new instance of an object); private (in current class only); protected (in current class or subclasses); readonly (cannot be changed after first initialization); static (methods can be called on the base class – an instance does not have to be created)


	Type
	Reference Type
	Built-in (object, string – written as ”XYZABC”)
	Interface Types (method parameter/return templates)
	Pointer Types (addresses of values)
	Self-describing Types
	Arrays (lists of objects of given type(s))
	Class Types
	Delegates (pointers to methods)
	Boxes Values (objects representing values)
	User-defined Reference Types


		Value Type
		Built-in Type
		Integer types (sbyte, short, int, long, byte,
		ushort, uint, ulong)
		Floating point types (float, double, decimal
		[128 bit])
		Boolean (bool [T/F])
		Character (char [single character – values
		written ’x’])
		User-defined Type
		Enumeration (named integer values)


	Complex Type
	Structure
	struc Name {string First; string Last};
	Name Jon, New; Jon.First=“Jon”; Jon.Last=“Melvin”; Name NewName;


	Array (subscripts are always surrounded with […]; subscripts go from 0, …)
	int[] Integers=new Int[32]; /* declare array Integers of 32 integers */
	/* create and initialize array of 3 string answers */
	string[] Answers=new string[] {“Yes”,”No”,”Maybe”}
	/* this fails; only constant length arrays allowed; Answer[0]=“Yes” */
	int a=5; int[] Array=new int[a];
	/* 2 dimensional arrays */
	string[][] Names=new string[2][];
	Names[0]=new string[]{"James","Joyce"};
	Names[1]=new string[3]{"E","B","White"}; /* Name[1,2]=‘White’ */
	Fields of given type are objects. Some methods are of object instance, some of base
	class. E.g., int i=5; string s=i.ToString; int[] Test int[](1,3,2); Array.Reverse(Test)
	changes order of elements to 2,3,1.
	Array.Sort(Test) changes order to 1,2,3.


	Enumeration
	public enum TimeOfDay {Morning=0,Afternoon=1,Evening=2};

	Enum Example:

		using System;
		namespace vi.Examples.Enum{
		enum TimeOfDay{Morning=1,Afternoon=2,Evening=3};
		class Class1{ static void Main(string[] args) {
		TimeOfDay Time;
		Time=TimeOfDay.Morning;
		Console.WriteLine(Greeting(Time));}
		static string Greeting(TimeOfDay Time) {
		switch(Time){
		case TimeOfDay.Morning: return "Good Morning";
		case TimeOfDay.Afternoon: return "Good Afternoon";
		case TimeOfDay.Evening: return "Good Evening";
		default: return "Hello";}}}}


	using System; using System.Data;
	namespace Table
	{class Class1{static void Main() {
	int i;
	DataSet ds=new DataSet();
	DataTable test=new DataTable("Test");
	test.Columns.Add(new DataColumn("test",typeof(int)));
	ds.Tables.Add(test);
	for (i=1;i<1000;i++) {DataRow r=ds.Tables["Test"].NewRow();
	r["test"]=i; ds.Tables["Test"].Rows.Add(r);};
	foreach(DataRow theRow in ds.Tables["Test"].Rows) {Console.WriteLine(theRow["test"]);};
	}
	}}


	using System;
	using System.Drawing;
	using System.Collections;
	using System.ComponentModel;
	using System.Windows.Forms;
	using System.Data;
	namespace WindowsApplication1 {public class Form1 : System.Windows.Forms.Form {
		private System.Windows.Forms.Button button1;
		private System.Windows.Forms.Label label1;
		private System.ComponentModel.Container components = null;

	public Form1(string args) {InitializeComponent(args);}

	protected override void Dispose( bool disposing ) {
	if(disposing) if(components != null) components.Dispose();
	base.Dispose( disposing );}

	private void InitializeComponent(string args) { this.button1 = new


	System.Windows.Forms.Button();
	this.label1 = new System.Windows.Forms.Label();
	this.SuspendLayout();

	this.button1.Location = new System.Drawing.Point(109, 208);
	this.button1.Name = "button1"; this.button1.TabIndex = 0; this.button1.Text = "Exit";
	this.button1.Click += new System.EventHandler(this.button1_Click);

	this.label1.Location = new System.Drawing.Point(70, 56);
	this.label1.Name = "label1"; this.label1.TabIndex = 1; this.label1.Text = args;
	this.label1.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
	this.label1.Size = new System.Drawing.Size(152, 23);
	this.Name = "Form1"; this.Text = "Sample Form";
	this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
	this.ClientSize = new System.Drawing.Size(292, 270);
	this.Controls.AddRange(new System.Windows.Forms.Control[] {this.label1,this.button1});
	this.ResumeLayout(false);}
	[STAThread] static void Main(string[] args) {Application.Run(new Form1(args[0]));}
	private void button1_Click(object sender, System.EventArgs e) {this.Close() ;}
	}}