Chapter 5 : Selected Software - SAKET-SK/Online-Electronic-Store-Project GitHub Wiki

The .NET Framework is a new computing platform that simplifies application development in the highly distributed environment of the Internet. The .NET Framework is designed to fulfill the following objectives:

To provide a consistent object-oriented programming environment, whether object code is stored and executed locally, executed locally but Internet-distributed, or executed remotely.
To provide a code-execution environment that minimizes software deployment and versioning conflicts.
To provide a code-execution environment that guarantees safe execution of code, including code created by an unknown or semi-trusted third party.
To provide a code-execution environment that eliminates the performance problems of scripted or interpreted environments.
To make the developer experience consistent across widely varying types of applications, such as Windows-based applications and Web-based applications.
To build all communication on industry standards to ensure that code based on ASP.NET hosts the runtime to provide a scalable, server-side environment for managed code. ASP.NET works directly with the runtime to enable Web Forms applications and XML Web services, both of which are discussed later in this topic.

ASP.NET

SERVER APPLICATION DEVELOPMENT:

Server-side applications in the managed world are implemented through runtime hosts. Unmanaged applications host the common language runtime, which allows your custom managed code to control the behavior of the server. This model provides you with all the features of the common language runtime and class library while gaining the performance and scalability of the host server.

The following illustration shows a basic network schema with managed code running in different server environments. Servers such as IIS and SQL Server can perform standard operations while your application logic executes through the managed code.

SERVER-SIDE MANAGED CODE:

ASP.NET is the hosting environment that enables developers to use the .NET Framework to target Web-based applications. However, ASP.NET is more than just a runtime host; it is a complete architecture for developing Web sites and Internet-distributed objects using managed code. Both Web Forms and XML Web services use IIS and ASP.NET as the publishing mechanism for applications, and both have a collection of supporting classes in the .NET Framework.

A Passive Web Server stores static Web Pages

An active Web Server generates dynamic Web Pages

ASP.NET Web Forms provide an easy and powerful way to build dynamic Web UI.
ASP.NET Web Forms pages can target any browser client (there are no script library or cookie requirements).
ASP.NET Web Forms pages provide syntax compatibility with existing ASP pages.
ASP.NET server controls provide an easy way to encapsulate common functionality.
ASP.NET ships with 45 built-in server controls. Developers can also use controls built by third parties.
ASP.NET server controls can automatically project both up level and down level HTML.
ASP.NET templates provide an easy way to customize the look and feel of list server controls.
ASP.NET validation controls provide an easy way to do declarative client or server data validation.

C#.NET

ADO.NET OVERVIEW

ADO.NET is an evolution of the ADO data access model that directly addresses user requirements for developing scalable applications. It was designed specifically for the web with scalability, statelessness, and XML in mind.

ADO.NET uses some ADO objects, such as the Connection and Command objects, and also introduces new objects. Key new ADO.NET objects include the DataSet, DataReader, and DataAdapter.

The following sections will introduce you to some objects that have evolved, and some that are new. These objects are:

Connections. For connection to and managing transactions against a database.
Commands. For issuing SQL commands against a database.
DataReaders. For reading a forward-only stream of data records from a SQL Server data source.
DataSets. For storing, Remoting, and programming against flat data, XML data and relational data.
DataAdapters. For pushing data into a DataSet and reconciling data against a database.

When dealing with connections to a database, there are two different options: SQL Server .NET Data Provider (System.Data.SqlClient) and OLE DB .NET Data Provider (System.Data.OleDb). In these samples, we will use the SQL Server .NET Data Provider. These are written to talk directly to Microsoft SQL Server. The OLE DB .NET Data Provider is used to talk to any OLE DB provider (as it uses OLE DB underneath).

Connections:

Connections are used to 'talk to' databases, and are represented by provider-specific classes such as SqlConnection. Commands travel over connections and resultsets are returned in the form of streams which can be read by a DataReader object, or pushed into a DataSet object.

Commands:

Commands contain the information that is submitted to a database, and are represented by provider-specific classes such as SqlCommand. A command can be a stored procedure call, an UPDATE statement, or a statement that returns results. You can also use input and output parameters, and return values as part of your command syntax. The example below shows how to issue an INSERT statement against the Northwind database.

DataReaders:

The DataReader object is somewhat synonymous with a read-only/forward-only cursor over data. The DataReader API supports flat as well as hierarchical data. A DataReader object is returned after executing a command against a database. The format of the returned DataReader object is different from a recordset. For example, you might use the DataReader to show the results of a search list in a web page.

DATASETS AND DATAADAPTERS:

DataSet

The DataSet object is similar to the ADO Recordset object, but more powerful, and with one other important distinction: the DataSet is always disconnected. The DataSet object represents a cache of data, with database-like structures such as tables, columns, relationships, and constraints. However, though a DataSet can and does behave much like a database, it is important to remember that DataSet objects do not interact directly with databases or other source data. This allows the developer to work with a programming model that is always consistent, regardless of where the source data resides. Data coming from a database, an XML file, from code, or user input can all be placed into DataSet objects. Then, as changes are made to the DataSet, they can be tracked and verified before updating the source data. The GetChanges method of the DataSet object actually creates a second DataSet that contains only the changes to the data.

This DataSet is then used by a DataAdapter (or other objects) to update the original data source. The DataSet has many XML characteristics, including the ability to produce and consume XML data and XML schemas. XML schemas can be used to describe schemas exchanged via Web Services. In fact, a DataSet with a schema can actually be compiled for type safety and statement completion.

DATAADAPTERS (OLEDB/SQL)

The DataAdapter object works as a bridge between the DataSet and the source data. Using the provider-specific SqlDataAdapter (along with its associated SqlCommand and SqlConnection) can increase overall performance when working with a Microsoft SQL Server database. For other OLE DB-supported databases, you would use the OleDbDataAdapter object and its associated OleDbCommand and OleDbConnection objects.

ADO.NET follows the process, figure below to connect to the database and retrieve data for the application.

SQL SERVER

A database management system, or DBMS, gives the user access to their data and helps them transform the data into information. Such database management systems include dBase, Paradox, IMS, SQL Server, and SQL Server. These systems allow users to create, update, and extract information from their database.

A database is a structured collection of data. Data refers to the characteristics of people, things, and events. SQL Server stores each data item in its own fields. In SQL Server, the fields relating to a particular person, thing or event are bundled together to form a single complete unit of data, called a record (it can also be referred to as raw or an occurrence). Each record is made up of a number of fields. No two fields in a record can have the same field name.

During an SQL Server Database design project, the analysis of your business needs identifies all the fields or attributes of interest. If your business needs change over time, you can define any additional fields or change the definition of existing fields.

SQL SERVER TABLES

SQL Server stores records relating to each other in a table. Different tables are created for the various groups of information. Related tables are grouped together to form a database.

PRIMARY KEY

Every table in SQL Server has a field or a combination of fields that uniquely identifies each record in the table. The Unique identifier is called the Primary Key, or simply the Key. The primary key provides the means to distinguish one record from all other in a table. It allows the user and the database system to identify, locate and refer to one particular record in the database.

RELATIONAL DATABASE

Sometimes, all the information of interest to a business operation can be stored in one table. SQL Server makes it very easy to link the data in multiple tables. Matching an employee to the department in which they work is one example. This is what makes SQL Server a relational database management system, or RDBMS. It stores data in two or more tables and enables you to define relationships between the table and enables you to define relationships between the tables.

FOREIGN KEY

When a field in one table matches the primary key of another field is referred to as a foreign key. A foreign key is a field or a group of fields in one table whose values match those of the primary key of another table.

REFERENTIAL INTEGRITY

Not only does SQL Server allow you to link multiple tables, it also maintains consistency between them. Ensuring that the data among related tables is correctly matched is referred to as maintaining referential integrity.

DATA ABSTRACTION

A major purpose of a database system is to provide users with an abstract view of the data. This system hides certain details of how the data is stored and maintained. Data abstraction is divided into three levels.

Physical level: This is the lowest level of abstraction at which one describes how the data is actually stored.

Conceptual Level: At this level of database abstraction, all the attributes and what data are actually stored are described, and the entries and relationships among them.

View level: This is the highest level of abstraction at which one describes only part of the database.

ADVANTAGES OF RDBMS

Redundancy can be avoided
Inconsistency can be eliminated
Data can be shared
Standards can be enforced
Security restrictions ca be applied
Integrity can be maintained
Conflicting requirements can be balanced
Data independence can be achieved.

DISADVANTAGES OF DBMS:

A significant disadvantage of the DBMS system is cost. In addition to the cost of purchasing of developing the software, the hardware has to be upgraded to allow for the extensive programs and the workspace required for their execution and storage. While centralization reduces duplication, the lack of duplication requires that the database be adequately backed up so that in case of failure the data can be recovered.