.Net Framework 2 fundamentals

CHAPTER -1FRAMEWORK FUNDAMENTALS

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By Harshana Weerasinghe (http://www.harshana.info) 2

Framework Fundamentals

Create a console or Windows Forms application in Visual Studio.

Add namespaces and references to system class libraries to a project.

Run a project in Visual Studio, set breakpoints, step through code, and watch the values of variables.


Types

Mainly 2 types in Microsoft .Net Value Type Reference Type


Value Types

Value types are variables that contain their data directly instead of containing a reference to the data stored elsewhere in memory. Instances of value types are stored in an area of memory called the stack, where the runtime can create, read, update, and remove them quickly with minimal overhead.

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Built-in Value Types


Other Value Types


Declare Value Types

<type> <VariableName> [= <Default Value>];

bool bolTestVariable = false;Nullable<bool> b = null; Orbool? b = null;


Create User-Defined Typesstruct Cycle{ // Private fields int _val, _min, _max;

// Constructor public Cycle(int min, int max) { _val = min; _min = min; _max = max; }

public int Value { get { return _val; } set { if (value > _max) _val = _min;

else { if (value < _min) _val = _max; else _val = value; } } }

public override string ToString() { return Value.ToString(); }

public int ToInteger() { return Value; }}


Using Operators (new in .NET 2.0)*

public static Cycle operator +(Cycle arg1, int arg2){ arg1.Value += arg2; return arg1;}

public static Cycle operator -(Cycle arg1, int arg2){ arg1.Value -= arg2; return arg1;}


Use User-Defined Types

Cycle degrees = new Cycle(0, 359);Cycle quarters = new Cycle(1, 4);for (int i = 0; i <= 8; i++){ degrees += 90; quarters += 1; Console.WriteLine("degrees = {0}, quarters = {1}",

degrees, quarters);}


Enumerations

enum Titles : int { Mr, Ms, Mrs, Dr };

Titles t = Titles.Dr;Console.WriteLine("{0}.", t); //

Displays "Dr."


Reference Types

Reference types store the address of their data, also known as a pointer, on the stack. The actual data that address refers to is stored in an area of memory called the heap. The runtime manages the memory used by the heap through a process called garbage collection. Garbage collection recovers memory periodically as needed by disposing of items that are no longer referenced.




Built-in Reference Types


Strings and String Buildersstring s = "this is some text to search";s = s.Replace("search", "replace");Console.WriteLine(s);

string s;

s = "wombat"; // "wombat“s += " kangaroo"; // "wombat kangaroo“s += " wallaby"; // "wombat kangaroo wallaby“s += " koala"; // "wombat kangaroo wallaby

koala”Console.WriteLine(s);


String Builder

using System.Text;

StringBuilder sb = new StringBuilder(30);sb.Append("wombat"); // Build string.sb.Append(" kangaroo");sb.Append(" wallaby");sb.Append(" koala");string s = sb.ToString(); // Copy result to

string.Console.WriteLine(s);


Create and Sort Arrays

// Declare and initialize an array.int[] ar = { 3, 1, 2 };

// Call a shared/static array method.Array.Sort(ar);

// Display the result.Console.WriteLine("{0}, {1}, {2}",

ar[0], ar[1], ar[2]);


Streams

Streams are another very common type because they are the means for reading from and writing to the disk and communicating across the network. The System.IO.Stream type is the base type for all task-specific stream types.


Streams Cont…

using System.IO;

// Create and write to a text fileStreamWriter sw = new StreamWriter("text.txt");sw.WriteLine("Hello, World!");sw.Close();

// Read and display a text fileStreamReader sr = new

StreamReader("text.txt");Console.WriteLine(sr.ReadToEnd());sr.Close();


Throw and Catch ExceptionsStreamReader sr = new StreamReader("text.txt");try{ Console.WriteLine(sr.ReadToEnd());}catch (Exception ex){ // If there are any problems reading the file, display an error

message Console.WriteLine("Error reading file: " + ex.Message);}finally{ // Close the StreamReader, whether or not an exception occurred sr.Close();}


Constructing Classes

public class Cycle{ // Private fields int _val, _min, _max; // Constructor public Cycle(int min, int

max) { _val = min; _min = min; _max = max; }

//Property public int Value { get { return _val; } set { _val = value; } }

//Method public string MyValue() { return _val.ToString(); } }


Inheritance – Animal Classclass Animal{ string m_Name; int m_Age;

public Animal(string _Name)

{ this.Name = _Name;

}

public string Name { get { return m_Name; }

set { m_Name = value; } }

public int Age { get { return m_Age; } set { m_Age = value; } } public string Speak() { return "Hello Animal"; }

}


Cat n Dog Classes

class Cat : Animal{ double m_Weight;

public double Weight { get { return m_Weight; } set { m_Weight = value; } } public string Speak() { return "Meaw, Meaw"; }}

class Dog : Animal{ //Default Ctor public Dog() { } //Other Ctor public Dog(string _Name,int _Age) : base(_Name)//Call Base Class Ctor { this.Age = _Age; } public string Speak() { if (this.Age >3) return " Grr.. Grr.."; else return " Buhh.. Buhh..";

}}


Interfaces

Interfaces, also known as contracts, define a common set of members that all classes that implement the interface must provide. For example, the IComparable interface defines the CompareTo method, which enables two instances of a class to be compared for equality. All classes that implement the IComparable interface, whether custom-created or built in the .NET Framework, can be compared for equality.


Sampleinterface IMessage{ // Send the message. Returns True is

success, False otherwise. bool Send(); // The message to send. string Message { get; set; } // The Address to send to. string Address { get; set; }}

class EmailMessage : IMessage{ public bool Send() { throw new Exception("The method or

operation is not implemented."); }

public string Message { get { throw new Exception("The method or

operation is not implemented."); } set { throw new Exception("The method or

operation is not implemented."); } }

public string Address { get { throw new Exception("The method or

operation is not implemented."); } set { throw new Exception("The method or

operation is not implemented."); } }}


Commonly used interfaces


Partial Classes - new in .NET 2.0

Partial classes allow you to split a class definition across multiple source files. The benefit of this approach is that it hides details of the class definition so that derived classes can focus on more significant portions.


Generics

Generics are part of the .NET Framework's type system that allows you to define a type while leaving some details unspecified. Instead of specifying the types of parameters or member classes, you can allow code that uses your type to specify it. This allows consumer code to tailor your type to its own specific needs.


Generics Cont..

class Obj{ public Object t; public Object u;

public Obj(Object _t, Object _u)

{ t = _t; u = _u; }}

class Gen<T, U>{ public T t; public U u;

public Gen(T _t, U _u) { t = _t; u = _u; }}


Generics Cont..

// Add two strings using the Obj classObj oa = new Obj("Hello, ", "World!");Console.WriteLine((string)oa.t + (string)oa.u);

// Add two strings using the Gen classGen<string, string> ga = new Gen<string, string>("Hello, ",

"World!");Console.WriteLine(ga.t + ga.u);

// Add a double and an int using the Obj classObj ob = new Obj(10.125, 2005);Console.WriteLine((double)ob.t + (int)ob.u);

// Add a double and an int using the Gen classGen<double, int> gb = new Gen<double, int>(10.125, 2005);Console.WriteLine(gb.t + gb.u);


Generics Cont..

// Add a double and an int using the Gen classGen<double, int> gc = new Gen<double, int>(10.125,

2005);Console.WriteLine(gc.t + gc.u);

// Add a double and an int using the Obj classObj oc = new Obj(10.125, 2005);Console.WriteLine((int)oc.t + (int)oc.u);

last line contains an error — the oc.t value is cast to an Int instead of to a double. Unfortunately, the compiler won't catch the mistake. Instead, a run-time exception is thrown when the runtime attempts to cast a double to an Int value.


Events

.Net Framework 2 fundamentals

Technology

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