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Outline
1
A Hacker’s Approach to C#
  • J.D. Melvin
  • Vision Implementers, Inc.
2
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
3
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
4
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());}
  • }
  • }
5
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])
6
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
7
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!)
8
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 ;
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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)
10
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
11
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)
12
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.
13
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]);
  • }}}
14
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";}}}}
15
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"]);};
  • }
  • }}
16
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
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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() ;}
  • }}