Object Oriented Programming Concepts

Object Oriented Concepts :-

Abstraction :- It allows you to show only necessary properties. Example RGB

Encapsulation :- Hide the inner complexity of the objects. Example Add to database, everything should be hided inside.

Abstraction and Encapsulation both will complement each other.

Inheritance :-

Inheritance helps to establish the parent-child relationship between classes. By doing so the child class will have the qualities of its parent plus the new qualities of himself.

Polymorphism :-

Poly mean “Many”. Depending on the condition the objects behavior changes. There are two kinds of polymorphism.

Static Polymorphism

                Method Overloading

                Operator Overloading

    public class Complex

    {

        private int real;

        public int Real

        { get { return real; } }

        private int imaginary;

        public int Imaginary

        { get { return imaginary; } }

        public Complex(int real, int imaginary)

        {

            this.real = real;

            this.imaginary = imaginary;

        }

        public static Complex operator +(Complex c1, Complex c2)

        {

            return new Complex(c1.Real + c2.Real, c1.Imaginary +                    c2.Imaginary);

        }

    }

Dynamic Polymorphism

                Method overriding

    public class Product

    {

        public int GetPrice(int quantity, int price)

        {

            return (quantity * price);

        }

        //Method Overridding

        public virtual string GetProductName()

        {

            return "Compressor";

        }

    }

    public class CommercialProduct : Product

    {

        public int GetPrice(int quantity, int price,int totalDiscount)

        {

            return (GetPrice(quantity, price) - totalDiscount);

        }

        public override string GetProductName()

        {

            return "Refrigerator";

        }

    }

Association, Aggregation and Composition :-

Assoication is nothing but “IS” a relationship between classes. Inheritance are type of IS a relationship.

Aggregation and Composition are nothing but “HAS” a relationship between classes. The difference between Aggregation and Compostion is, the lifetime of the object composite relationship will be same whereas in Aggreation relationship it is not.

Raja has a heart is an example for composition because both cant exist independently.

Raja has a shirt is an example for Aggregation because both can exist independently.

Logging Application Block Sample

How to configure Exception Handling and Logging Application Block(Database Logging).

1.       Execute the below DB scripts to create Tables and Storced procedures in the database.

Create Table Scripts :-

CREATE TABLE [dbo].[Log](

      [LogID] [int] IDENTITY(1,1) NOT NULL,

      [EventID] [int] NULL,

      [Priority] [int] NOT NULL,

      [Severity] [nvarchar](32) NOT NULL,

      [Title] [nvarchar](256) NOT NULL,

      [Timestamp] [datetime] NOT NULL,

      [MachineName] [nvarchar](32) NOT NULL,

      [AppDomainName] [nvarchar](512) NOT NULL,

      [ProcessID] [nvarchar](256) NOT NULL,

      [ProcessName] [nvarchar](512) NOT NULL,

      [ThreadName] [nvarchar](512) NULL,

      [Win32ThreadId] [nvarchar](128) NULL,

      [Message] [nvarchar](1500) NULL,

      [FormattedMessage] [ntext] NULL,

 CONSTRAINT [PK_Log] PRIMARY KEY CLUSTERED

(

      [LogID] ASC

)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]

) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

CREATE TABLE [dbo].[Category](

      [CategoryID] [int] IDENTITY(1,1) NOT NULL,

      [CategoryName] [nvarchar](64) NOT NULL,

 CONSTRAINT [PK_Categories] PRIMARY KEY CLUSTERED

(

      [CategoryID] ASC

)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]

) ON [PRIMARY]

CREATE TABLE [dbo].[CategoryLog](

      [CategoryLogID] [int] IDENTITY(1,1) NOT NULL,

      [CategoryID] [int] NOT NULL,

      [LogID] [int] NOT NULL,

 CONSTRAINT [PK_CategoryLog] PRIMARY KEY CLUSTERED

(

      [CategoryLogID] ASC

)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]

) ON [PRIMARY]

GO

ALTER TABLE [dbo].[CategoryLog]  WITH CHECK ADD  CONSTRAINT [FK_CategoryLog_Category] FOREIGN KEY([CategoryID])

REFERENCES [dbo].[Category] ([CategoryID])

GO

ALTER TABLE [dbo].[CategoryLog] CHECK CONSTRAINT [FK_CategoryLog_Category]

GO

ALTER TABLE [dbo].[CategoryLog]  WITH CHECK ADD  CONSTRAINT [FK_CategoryLog_Log] FOREIGN KEY([LogID])

REFERENCES [dbo].[Log] ([LogID])

GO

ALTER TABLE [dbo].[CategoryLog] CHECK CONSTRAINT [FK_CategoryLog_Log]

Create Stored Procedures Script :-

CREATE PROCEDURE [dbo].[AddCategory]

      -- Add the parameters for the function here

      @CategoryName nvarchar(64),

      @LogID int

AS

BEGIN

      SET NOCOUNT ON;

    DECLARE @CatID INT

      SELECT @CatID = CategoryID FROM Category WHERE CategoryName = @CategoryName

      IF @CatID IS NULL

      BEGIN

            INSERT INTO Category (CategoryName) VALUES(@CategoryName)

            SELECT @CatID = @@IDENTITY

      END

      EXEC InsertCategoryLog @CatID, @LogID

      RETURN @CatID

END

CREATE PROCEDURE [dbo].[ClearLogs]

AS

BEGIN

      SET NOCOUNT ON;

      DELETE FROM CategoryLog

      DELETE FROM [Log]

    DELETE FROM Category

END

CREATE PROCEDURE [dbo].[InsertCategoryLog]

      @CatID int,

      @LogID int

AS

BEGIN

      SET NOCOUNT ON;

INSERT INTO CATEGORYLOG(CATEGORYID,LOGID) VALUES(@CatID,@LogID)

END

CREATE PROCEDURE [dbo].[WriteLog]

(

      @EventID int,

      @Priority int,

      @Severity nvarchar(32),

      @Title nvarchar(256),

      @Timestamp datetime,

      @MachineName nvarchar(32),

      @AppDomainName nvarchar(512),

      @ProcessID nvarchar(256),

      @ProcessName nvarchar(512),

      @ThreadName nvarchar(512),

      @Win32ThreadId nvarchar(128),

      @Message nvarchar(1500),

      @FormattedMessage ntext,

      @LogId int OUTPUT

)

AS

      INSERT INTO [Log] (

            EventID,

            Priority,

            Severity,

            Title,

            [Timestamp],

            MachineName,

            AppDomainName,

            ProcessID,

            ProcessName,

            ThreadName,

            Win32ThreadId,

            Message,

            FormattedMessage

      )

      VALUES (

            @EventID,

            @Priority,

            @Severity,

            @Title,

            @Timestamp,

            @MachineName,

            @AppDomainName,

            @ProcessID,

            @ProcessName,

            @ThreadName,

            @Win32ThreadId,

            @Message,

            @FormattedMessage)

      SET @LogID = @@IDENTITY

      RETURN @LogID

After creating the tables and stored procedures,  please make sure that you have provided the execution grants to the Stored procedures properly.

please open the web.config using Enterprise Library configuration tool.

1.       Make sure that the web.config already has the connectionstring tag set.

2.       Add Logging Application Block to the config as mentioned below.

3.       As we are planning to do the database logging, add the database trace listener as mentioned below.

4.        Select the corresponding database instance name.

5.       Add a new category and name it as DBCategory

6.       Add a new Listener reference to the category.

7.       Add the reference to Database Trace listener.

8.       Add Exception Handling Application block to the config todo set the exception policies.

9.       Add a exception Policy and exception type as mentioned below and give a proper name to exception policy.

10.   Add the logging handler to the exception.

11.   Select the log category and select t the Format type as textexceptionformat.

12.   Open the .NET application add the below references to the application.

Microsoft.Practices.EnterpriseLibrary.ExceptionHandling

Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging

Microsoft.Practices.EnterpriseLibrary.Logging

Microsoft.Practices.EnterpriseLibrary.Logging.Database

13.   Add the below sample code in button click or page load event and run the application.

            try

            {

                throw(new Exception("Test Logging Application Block"));

            }

            catch (Exception ex)

            {

                    ExceptionPolicy.HandleException(ex, "Policy1");

            }