.Net Framework Fundamentals

.Net Framework Fundamentals

.Net Framework Fundamentals

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Harshana Weerasinghe

April 10, 2012
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  1. Harshana Weerasinghe http://www.harshana.info http://Blog.harshana.info

  2.  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. By Harshana Weerasinghe (http://www.harshana.info) 2
  3.  Mainly 2 types in Microsoft .Net  Value Type

     Reference Type By Harshana Weerasinghe (http://www.harshana.info) 3
  4.  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. By Harshana Weerasinghe (http://www.harshana.info) 4
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  7. <type> <VariableName> [= <Default Value>];  bool bolTestVariable = false;

     Nullable<bool> b = null; Or  bool? b = null; By Harshana Weerasinghe (http://www.harshana.info) 7
  8. struct 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; } } By Harshana Weerasinghe (http://www.harshana.info) 8
  9. 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; } By Harshana Weerasinghe (http://www.harshana.info) 9
  10. 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); } By Harshana Weerasinghe (http://www.harshana.info) 10
  11. enum Titles : int { Mr, Ms, Mrs, Dr };

    Titles t = Titles.Dr; Console.WriteLine("{0}.", t); // Displays "Dr." By Harshana Weerasinghe (http://www.harshana.info) 11
  12.  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. By Harshana Weerasinghe (http://www.harshana.info) 12
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  14. string 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); By Harshana Weerasinghe (http://www.harshana.info) 14
  15. 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); By Harshana Weerasinghe (http://www.harshana.info) 15
  16. // 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]); By Harshana Weerasinghe (http://www.harshana.info) 16
  17.  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. By Harshana Weerasinghe (http://www.harshana.info) 17
  18. using System.IO; // Create and write to a text file

    StreamWriter sw = new StreamWriter("text.txt"); sw.WriteLine("Hello, World!"); sw.Close(); // Read and display a text file StreamReader sr = new StreamReader("text.txt"); Console.WriteLine(sr.ReadToEnd()); sr.Close(); By Harshana Weerasinghe (http://www.harshana.info) 18
  19. StreamReader 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(); } By Harshana Weerasinghe (http://www.harshana.info) 19
  20. 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(); } } By Harshana Weerasinghe (http://www.harshana.info) 20
  21. class 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"; } } By Harshana Weerasinghe (http://www.harshana.info) 21
  22. 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.."; } } By Harshana Weerasinghe (http://www.harshana.info) 22
  23.  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. By Harshana Weerasinghe (http://www.harshana.info) 23
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  25. interface 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."); } } } By Harshana Weerasinghe (http://www.harshana.info) 25
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  27.  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. By Harshana Weerasinghe (http://www.harshana.info) 27
  28.  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. By Harshana Weerasinghe (http://www.harshana.info) 28
  29. 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; } } By Harshana Weerasinghe (http://www.harshana.info) 29
  30. // Add two strings using the Obj class Obj oa

    = new Obj("Hello, ", "World!"); Console.WriteLine((string)oa.t + (string)oa.u); // Add two strings using the Gen class Gen<string, string> ga = new Gen<string, string>("Hello, ", "World!"); Console.WriteLine(ga.t + ga.u); // Add a double and an int using the Obj class Obj ob = new Obj(10.125, 2005); Console.WriteLine((double)ob.t + (int)ob.u); // Add a double and an int using the Gen class Gen<double, int> gb = new Gen<double, int>(10.125, 2005); Console.WriteLine(gb.t + gb.u); By Harshana Weerasinghe (http://www.harshana.info) 30
  31. // Add a double and an int using the Gen

    class Gen<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 class Obj 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. By Harshana Weerasinghe (http://www.harshana.info) 31
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