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Sunday, March 9, 2008
Sunday, March 2, 2008
OOPL Comparison
The following table shows some similarities and differences in features and the use of terms and concepts in Smalltalk, C++, and Java.
OO Concept/syntax | Smalltalk | C++ | Java | |
Abstract class | Concept exists, no mechanism for enforcement | A class with a pure virtual function can't be instantiated | Classes may be declared abstract | |
Assignment operator | := | = | = | |
Character constant | $c | 'c' | 'c' | |
Class | Class | Class | Class | |
Class method (corresponds to a message sent to the class rather than an instance) | Class method | Static function member | Class (or static) method | |
Class variable (data associated with the class, not an instance) | Class variable | Static data member | Class field | |
Comment | "Comment" | // Comment | // Comment | |
Dynamic binding | Unrestricted | Only subclasses of the declared class | Subclasses of the declared class or implementations of the declared interface | |
Equality test (see also identity test) | = | == | equals() | |
Finalization of instances before deletion (e.g., to release operating system resources) | Some implementations support finalize method | Destructor function | finalize method is standard | |
Garbage collection (automatic memory management) | Garbage collection is standard | No garbage collection - programmer explicitly manages memory | Garbage collection is standard | |
Identity test (see also Equality test) | == | same as equality | == | |
Inheritance | Single inheritance only | Multiple inheritance | Single inheritance only | |
Initialization of instances | Override new method | Constructor function | Constructor function | |
Instance data or state | Instance variable | Data member | Instance field | |
Interface contract (specifies the public interface to classes that implement it) | No corresponding construct | No corresponding construct | Interface | |
Message | Message | Member function call | Method invocation | |
Message send syntax | anObject doIt | anObject.doIt() (direct) | anObject.doIt() | |
Method | Method | Member function | Method | |
Method argument syntax | methodName: argument (keyword method) | memberFunctionName(argument) | methodName(argument) | |
Method return | ^ (caret) | return | return | |
Object (root of all classes) | Class Object | No corresponding class | Class Object | |
Operator overloading (an aspect of polymorphism; different operator behavior based on receiver type) | Any operator can be overloaded | Any operator can be overloaded | Only methods can be overloaded, not built-in operators such as +, - , * | |
Pointers | No explicit storage pointers | Explicit use of storage pointers and pointer arithmetic | No explicit storage pointers | |
Self (the object executing a method) | self | this (usually not written) | this (usually not written) | |
String constant | 'string constant' | "string constant" | "string constant" | |
Subclass | Subclass | Derived class | Subclass | |
Superclass | Superclass | Base class | Superclass | |
Superclass method invocation | super | :: (scoping operator, more general than Smalltalk or Java capability) | super() | |
Wednesday, January 9, 2008
ASP.NET
The Microsoft .NET Framework
The .NET Framework is the infrastructure for the Microsoft .NET platform.
The .NET Framework is an environment for building, deploying, and running Web applications and Web Services.
Microsoft's first server technology ASP (Active Server Pages), was a powerful and flexible "programming language". But it was too code oriented. It was not an application framework and not an enterprise development tool.
The Microsoft .NET Framework was developed to solve this problem.
.NET Frameworks keywords:
- Easier and quicker programming
- Reduced amount of code
- Declarative programming model
- Richer server control hierarchy with events
- Larger class library
- Better support for development tools
The .NET Framework consists of 3 main parts:
Programming languages:
- C# (Pronounced C sharp)
- Visual Basic (VB .NET)
- J# (Pronounced J sharp)
Server technologies and client technologies:
- ASP .NET (Active Server Pages)
- Windows Forms (Windows desktop solutions)
- Compact Framework (PDA /
Development environments:
- Visual Studio .NET (VS .NET)
- Visual Web Developer
This tutorial is about ASP.NET.
ASP.NET 2.0
ASP.NET 2.0 improves upon ASP.NET by adding support for several new features.
You can read more about the differences between ASP.NET 2.0 and ASP.NET in the next chapter of this tutorial.
ASP.NET 3.0
ASP.NET 3.0 is not a new version of ASP.NET. It's just the name for a new ASP.NET 2.0 framework library with support for Windows Presentation Foundation, Windows Communication Foundation, Windows Workflow Foundation; and Windows CardSpace.
These topics are not covered in this tutorial.
Differences between ASP and ASP.NET
ASP.NET has better language support, a large set of new controls and XML based components, and better user authentication.
ASP.NET provides increased performance by running compiled code.
ASP.NET code is not fully backward compatible with ASP.
New in ASP.NET
- Better language support
- Programmable controls
- Event-driven programming
- XML-based components
- User authentication, with accounts and roles
- Higher scalability
- Increased performance - Compiled code
- Easier configuration and deployment
- Not fully ASP compatible
Language Support
ASP.NET uses the new ADO.NET.
ASP.NET supports full Visual Basic, not VBScript.
ASP.NET supports C# (C sharp) and C++.
ASP.NET supports JScript as before.
ASP.NET Controls
ASP.NET contains a large set of HTML controls. Almost all HTML elements on a page can be defined as ASP.NET control objects that can be controlled by scripts.
ASP.NET also contains a new set of object oriented input controls, like programmable list boxes and validation controls.
A new data grid control supports sorting, data paging, and everything you expect from a dataset control.
Event Aware Controls
All ASP.NET objects on a Web page can expose events that can be processed by ASP.NET code.
Load, Click and Change events handled by code makes coding much simpler and much better organized.
ASP.NET Components
ASP.NET components are heavily based on XML. Like the new AD Rotator, that uses XML to store advertisement information and configuration.
User Authentication
ASP.NET supports forms-based user authentication, including cookie management and automatic redirecting of unauthorized logins.
(You can still do your custom login page and custom user checking).
User Accounts and Roles
AS .NET allows for user accounts and roles, to give each user (with a given role) access to different server code and executables.
High Scalability
Much has been done with ASP.NET to provide greater scalability.
Server to server communication has been greatly enhanced, making it possible to scale an application over several servers. One example of this is the ability to run XML parsers, XSL transformations and even resource hungry session objects on other servers.
Compiled Code
The first request for an ASP.NET page on the server will compile the ASP.NET code and keep a cached copy in memory. The result of this is greatly increased performance.
Easy Configuration
Configuration of ASP.NET is done with plain text files.
Configuration files can be uploaded or changed while the application is running. No need to restart the server. No more metabase or registry puzzle.
Easy Deployment
No more server restart to deploy or replace compiled code. ASP.NET simply redirects all new requests to the new code.
Compatibility
ASP.NET is not fully compatible with earlier versions of ASP, so most of the old ASP code will need some changes to run under ASP.NET.
To overcome this problem, ASP.NET uses a new file extension ".aspx". This will make ASP.NET applications able to run side by side with standard ASP applications on the same server.
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