8.1 Overview of .NET

ASP.NET is the web development element of Microsoft's .NET platform. N-tier programming methodology is at the core of ASP.NET and the .NET platform. This methodology uses an object-oriented approach for dividing business logic, data access, and presentation logic. This separation, almost nonexistent in ASP 3.0, allows designers to easily retool business logic for use on platforms other than web browsers. It also allows developers to easily provide hooks into an application's logic by sharing business logic as XML web services.

The .NET Framework, sometimes referred to as the Base Class Library (BCL), is an extensive library of classes that provide basic functionality. By using these classes, developers can decrease development time with comprehensive implementations for data access, sending email, XML document manipulation, and much more.

The .NET Framework also allows developers a choice of programming languages, including JScript.NET, C# (pronounced "C sharp"), and Visual Basic.NET (VB.NET). Accessing the Framework varies only slightly across these three languages. A single ASP.NET application can mix modules written in different languages. Following are three analogous code snippets in the three languages. Each example displays "Hello World!" on the screen when the web page loads.

Visual Basic.NET example:

Sub Page_Load (Sender As Object, E As EventArgs)
  HelloWorld.Text = "Hello World!"
End Sub

C# example:

public void Page_Load (Object Sender, EventArgs E) {
  HelloWorld.Text = "Hello World!";

JScript.NET example:

Public void Page_Load (Object Sender, EventArgs E) {
  HelloWorld.Text = "Hello World!";

The .NET platform also uses the common type system (CTS) to map common datatypes among all supported .NET languages. This means a .NET object built in C# can pass parameters to a VB.NET object without a problem.

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