Implementing a Data Access Layer in C#

A Data Access Layer is an important layer in the architecture of any software.  This layer is responsible for communicating with the underlying database.  Making this layer provider independent can ensure multi database support with ease.  This article discusses implementation of a provider independent Data Access Layer in C#.

ADO.NET Data Providers

The following are the major ADO.NET data providers.

• SQL Server Data Provider


• Oracle Data Provider


• Odbc Data Provider


• OleDB Data Provider

Difference between Finalize() and Dispose()

 Some quick points on Finalize() and Dispose() in C#:

1. Finalize() is the C# equivalent of destructor   ~Object() syntax in C#. In VB.Net you implement the Finalize() by overriding it. But, in C# the compiler translates the destructor to a Finalize() method.

2. Finalize() can NOT be overridden or called in C#.

3. Since, Finalize() is called by the Garbage Collector, it is non-deterministic.

4. Dispose() has to be implemented in classes implementing IDispose interface.

5. Its the right place for freeing-up unmanaged resources like file, handles, and connections etc.

6. Dispose() method is called explicitely in the code itself.

7. Dispose() method is automatically called (for objects which implement IDispose), when used in a "using" statement.

Difference between Finalize and Dispose Method in .NET

C# Provides two special methods that are used to release the instance of a class from memory, Finalize() and Dispose().

Finalize():

The Finalize destructor is a special method that is called from the class to which it belongs or from the derived class. The Finalize() destructor is called after the last reference to an object is released from the memory. The .Net Framework automatically runs the Finalize() destructor to destroy objects in the memory. However, it is important to remember that the Finalize() destructor may not execute immediately when an object loses scope. It is called by CLR using reference-tracing garbage collection, the CLR periodically check for objects that are not used by the application. When such an object is found, the Finalize() destructor is called automatically and the garbage collector of the CLR release the object from the memory.Dispose():

The Dispose() method is called to release a resource, such as database connection, as soon as the object using such a resource is no longer in use. Unlike the Finalize() destructor, the Dispose() method is not called automatically and you must explicitly call it from a client application when an object is no longer needed. The IDisposable interface contains the Dispose() method. Therefore , to call the Dispose() method, the class must implement the IDisposable interface.

Database Concept

What is RDBMS?
Relational Data Base Management Systems (RDBMS) are database management systems that maintain data records and indices in tables. Relationships may be created and maintained across and among the data and tables. In a relational database, relationships between data items are expressed by means of tables. Interdependencies among these tables are expressed by data values rather than by pointers. This allows a high degree of data independence. An RDBMS has the capability to recombine the data items from different files, providing powerful tools for data usage.

What is normalization?
Database normalization is a data design and organization process applied to data structures based on rules that help build relational databases. In relational database design, the process of organizing data to minimize redundancy. Normalization usually involves dividing a database into two or more tables and defining relationships between the tables. The objective is to isolate data so that additions, deletions, and modifications of a field can be made in just one table and then propagated through the rest of the database via the defined relationships.

Handler Tutorial

Handler Concept in ASP.NET

Some ASP.NET files are dynamically generated. They are generated with C# code or disk resources. These files do not require web forms. Instead, an ASHX generic handler is ideal. It can dynamically return an image from a query string, write XML, or any other data.

HTTP handlers are the .NET components that implement the System.Web.IHttpHandler interface. Any class that implements the IHttpHandler interface can act as a target for the incoming HTTP requests. HTTP handlers are somewhat similar to ISAPI extensions. One difference between HTTP handlers and ISAPI extensions is that HTTP handlers can be called directly by using their file name in the URL, similar to ISAPI extensions.

Extension Method In LINQ

Extension Methods

Extension methods are one important piece of the query architecture. Extension methods combine the flexibility of "duck typing" made popular in dynamic languages with the performance and compile-time validation of statically-typed languages. With extension methods third parties may augment the public contract of a type with new methods while still allowing individual type authors to provide their own specialized implementation of those methods.

Extension methods are defined in static classes as static methods, but are marked with the [System.Runtime.CompilerServices.Extension] attribute in CLR metadata. Languages are encouraged to provide a direct syntax for extension methods. In C#, extension methods are indicated by the this modifier which must be applied to the first parameter of the extension method.