EXCEPTIONS AND OBJECT LIFE TIMEMr. G.C.Deshpande

Lecturer, CSE@KLS.GIT

Topic Level Objectives To confabulate about handling runtime anomalies in

the code base through the use of structured exception handling.

To examine the memory management process using the .NET garbage collector. To familiarize the C# keywords such as try, catch, throw and finally.

To examine the distinction between application-level and system-level exceptions.

To inspect various tools within Visual Studio 2012 to debug the exceptions.

To elucidate the role of application roots, object generations, and the System.GC type.

To confabulate disposable objects (via the IDisposable interface) and finalization process (via the System.Object.Finalize() method).

Intended Learning Outcomes1. Investigate various tools within Visual Studio 2012 to debug the exceptions [L 4].

2. Manage the memory using .NET garbage collector [L 3].

3. Clarify the distinction between classes, objects and references [L 2].

4. Explain the role of application roots [L 2].

5. Determine the objects reachable by application roots [L 2].

6. Describe System.GC members and their meaning in life [L 1].

7. Illustrate select members of System.GC type [L 5].

8. Explain the finalization process [L 2].

9. Implement finalizable and disposable objects [L 3].

10. Explain a formalized diaposal pattern [L 2].

11. Define anomaly-centric terms [L 1].

12. Explain the role of .NET exception handling and its atoms [L 2].

13. Explain various properties in configuring the state of an exception [L 2].

14. Differentiate between system level exceptions and application level exceptions [L 4].

15. Build custom/application level exceptions [L 5].

16. Explain the processing of multiple exceptions and the finally block [L 2].

17. Demonstrate the debugging of unhandled exceptions using visual studio 2012 [L 3].

Structured Exception Handling [SEH] Bugs: Error made by the programmer

User Errors: Error made by the user

Exceptions: Really exceptional circumstances !!!.. Runtime anomalies that are difficult to account for while programming your application.

SEH : Dealing with runtime anomalies.

Role of .NET Exception Handling

Structured Exception Handling [SEH] Lot of Numerical codes

Lack of symmetry

SEH : Unified approach to exceptional handling common to all languages

Human readable description of errors

The Atoms of .NET Exception Handling

The System.Exception Base Class

The System.Exception Base Class

Core members of System.Exception type

Core members of System.Exception type

The simplest possible example

The simplest possible example

The simplest possible example

The simplest possible example

The simplest possible example

Throwing a General Exception

Catching Exceptions

Catching Exceptions

Catching Exceptions

Defining the Pillars of OOPEncapsulation: How does this language hide an object’s internal implementation details and preserve data integrity? Inheritance: How does this language promote code reuse? Polymorphism: How does this language let you treat related objects in a similar way?

Role of Encapsulation

Role of Inheritance [ is-a ]

Role of Inheritance [ has-a ]

Role of Polymorphism

Role of Polymorphism

C# Access Modifiers

C# Access Modifiers

The first pillar: Encapsulation

The first pillar: Encapsulation

Object’s internal data should not be directly accessible from an object instanceAlter the state of an object indirectly using

Accessors (get) and Mutators (set) .Net property

Black Box Programming

Traditional Encapsulation

Traditional Encapsulation

Encapsulation using Accessors and Mutators

Encapsulation using Accessors and Mutators

Encapsulation using .Net Properties

Encapsulation using .Net Properties

Encapsulation using .Net Properties

Encapsulation using .Net Properties

Controlling Visibility Levels of Properties

read-only : omit the set blockwrite-only : omit the get block

Chaining of Constructors

Chaining of Constructors

Basic Mechanics of Inheritance

Basic Mechanics of Inheritance

Basic Mechanics of Inheritance

The sealed keyword

Inheritance

Inheritance

Controlling the base class creation

Controlling the base class creation

Controlling the base class creation Some properties may be readonly

Inefficient way of creating a constructor: since base class

Default constructor is called before the logic of derived class constructor

Controlling the base class creation

Arrays in C# An array is a set of data items, accessed using a numerical index

An array is a set of contiguous data points of the same type

Arrays in C#

C# Array Initialization Syntax

Implicitly typed local arrays

Array of objects

Multidimensional Arrays [ Rectangular ]Declarationint[,] myArray = new int[4,2];

int[,,] myArray = new int [4,2,3];

Initializationint[,] myArray = new int[,] {{1,2}, {3,4}, {5,6}, {7,8}};int[,] myArray = {{1,2}, {3,4}, {5,6}, {7,8}};

int[,] myArray;myArray = new int[,] {{1,2}, {3,4}, {5,6}, {7,8}}; // OKmyArray = {{1,2}, {3,4}, {5,6}, {7,8}}; // Error

Multidimensional Arrays [ Rectangular ]

Multidimensional Arrays [ Jagged ]

A jagged array is an array whose elements are arrays.

The elements of a jagged array can be of different dimensions and sizes.

A jagged array is sometimes called an "array-of-arrays.“ 

Declaration

int[][] myJaggedArray = new int[3][];

Initialization

myJaggedArray[0] = new int[5];

myJaggedArray[1] = new int[4];

myJaggedArray[2] = new int[2];

myJaggedArray[0] = new int[] {1,3,5,7,9}; myJaggedArray[1] = new int[] {0,2,4,6}; myJaggedArray[2] = new int[] {11,22};

Multidimensional Arrays [ Jagged ]Initialization

int[][] myJaggedArray = new int [][] { new int[] {1,3,5,7,9}, new int[] {0,2,4,6}, new int[] {11,22}

};

int[][] myJaggedArray = { new int[] {1,3,5,7,9}, new int[] {0,2,4,6}, new int[] {11,22}

};

Multidimensional Arrays [ Jagged ]Initialization

// Assign 33 to the second element of the first array: myJaggedArray[0][1] = 33;

// Assign 44 to the second element of the third array: myJaggedArray[2][1] = 44;

Mixing of arraysint[][,] myJaggedArray = new int [3][,] {

new int[,] { {1,3}, {5,7} },new int[,] { {0,2}, {4,6}, {8,10} }, new int[,] { {11,22}, {99,88}, {0,9} }

};

Multidimensional Arrays [ Jagged ]

The System.Array Base Class

Methods and Parameter Modifiers

Methods and Parameter Modifiers

Default Parameter Passing Behavior

The out Modifier

The out Modifier

The ref Modifier

The params Modifier

The params Modifier

Defining Optional Parameters

Defining Optional Parameters

Value Types and Reference Types

Value Types and Reference Types

BoxingConversion from value type to reference type

int m=100;

object om=m; //creates a box to hold m

int m=100;

object om=(object)m; //c-style casting

int m=10;

object om=m;

m=20;

console.writeline(m); //m=20

console.writeline(om); //om=10

UnboxingConversion from reference type to value type

int m=10;

object om=m; //box m

int n=(int)om; //unbox om

int m=500;

object om=m

byte n=(byte)om; // run-time error

Remember: We can only unbox a variable that has previously been boxed

References

1] Andrew Troelsen, Pro C# with .NET 3.0, Special Edition,

Dream tech Press, India, 2007.

2] E. Balagurusamy, Programming in C#, 5th Reprint, Tata McGraw Hill,

2004 (For Programming Examples).

3] Tom Archer, Inside C#, WP Publishers, 2001.

4] Herbert Schildt, C#: The Complete Reference, TMH, 2004. 

5] Yashavant Kanetkar, C#.NET fundas, First Edition, BPB Publications,

2002

 

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