A review of Visual Basic.NET cannot be undertaken before understanding the .NET platform. In this part, I will review the .NET platform to provide a better understanding to Visual Basic.NET
We have had the .NET platform installed recently on our machines at work, and although I am not personally involved in programming, I do have some friends in the programming section ;-)
Lets look into the latest offering from the Microsoft stables. The. NET platform is a very important and path-breaking suite of protocols and languages, which are designed to make programming the web-based applications, a lot easier. It uses XML as the basis for the integration of differing suites.
I will focus on the whole. NET platform, rather than delve into individual components like ASP.NET, VB.NET, C#, etcetera. I will try and review .NET as least technically as I can, however, please bear with me if it gets a bit dense. In case you don’t understand any part, please leave a comment and I will clarify better.
The web is the most important computer system. However the web is rather different from traditional PC systems and this has important effects on software development. For example the web comprises of many loosely coupled machines, which are heterogenous in nature; the web is unreliable and is not centrally administered. The Microsoft .net system is a system for developing software for web-based systems.
Why do we need web-based applications? With the interlinking of many resources, there is a need for sharing access to remote data sources. Also, it is easier to upgrade software centrally (thin-client), rather than through individual desktops (Fat clients).
In the .NET platform, the managed code runs within a new runtime environment. Code from any source language (c, c++, c#, Java. Etc), can be compiled to a common Intermediate Language (CIL)
CIL is similar to the Java Byte Code and its workings are similar to the workings of the Java Virtual Machine
The .NET platform has better support for components ( compared with COM). The new component assemblies—extensible meta information format—( Assemblies are discussed in greater detail below )provide a simpler model for component interaction. It is easier to deploy components, as there is no need for them to be registered in the registry of the Operating System. This, of course, provides for better control over security. The fine grain access control security, allows language interworking. You can work on more than 2 languages simultaneously! The .NET platform supports inter-language inheritance, exception handling, garbage collection, debugging and profiling. There are common class libraries (including WinForms for creating GUIs)
An assembly is a collection of one or more “binary” files that together constitute a single software component. It contains exactly one entry point (dllMain, WinMain or Main). The hash values ensure none of the files can be changed after the assembly is created, and all of the files in an assembly must be deployed together.
With the COM component model, whenever a component is to be updated, an entirely new GUID had to be assigned to it. In the .NET component model, assemblies are given a simple name that remains constant, plus a version number that changes with each update, eg:
System.Web.Services 1.0.3300.0
Assemblies can be given a globally unique “strong” name by including a public key that is generated from the contents of the assembly using a corresponding private key.
The Common Type System is a rich type system intended to support the complete implementation of a wide range of programming languages. The Meta Data is a common interchange mechanism for use between tools that manipulate programs (compilers, debuggers, etc.) and the Virtual Execution System.
When you finish writing a program, it goes to the compiler before it is executed. This is done to check if there are any errors in your programming. When a compiler produces CIL, it also produces metadata that describes the types the code defines, the assemblies the code references, and other data used by the runtime environment. The CIL and metadata are contained in a portable executable (PE) file. This file format enables the Windows operating system to recognize Common Language Runtime images. The presence of metadata in the file along with the CIL enables the code to describe itself, which means that there is no need for type libraries or IDLs. The runtime locates and extracts the metadata from the file as necessary during execution.
For objects to be able to understand each other no matter what language compiler they are compiled with, ( eg: in C, C++, Java , or any other programming language) they must expose to callers only those data types and features that are common to all the languages they need to interoperate with. For this reason, the runtime has identified a set of language features called the Common Language Specification (CLS), which includes the basic language features needed by many applications.
Security features of .net
Applications are executed inside a security context called an application domain. Application domains can be configured to disallow execution of unmanaged or unverifiable code as well as restricting access to system resources such as the local file system and the registry. Standard application domains exist for:
–command line execution
–objects hosted inside Internet Explorer
–ASP.NET (server-side
Installation of the .NET platform
There are many horror stories floating on the Internet over the installation. Most of the users have said that .NET installation causes their hard drive to crash!! We are lucky in that our company had the guys from Microsoft to come and Install .NET!!
Essentially the install is divided into three parts
Windows Component Update - This will bring Windows 2000 to Service Pack 2, update all the latest drivers and give you IE 6.
The Program itself - In total this can take nearly 2 GB in space. Remove C++ with related help files, and it comes down by at least 800 MB. If, with all that Hard drive capacity you are down to 4 GB or less, then you have more serious problems to consider :-)
The update - If you have a net connection, the system encourages you to get online to download updates and patches. Highly recommended.
The DVD install is the fastest but regardless, you must expect at least one reboot if your Windows 2000 components need updating. If you have Visual Studio 6 ( or less, but why would you have less ;-) installed on your machine, it will not be affected in any way shape or form. In fact, since the program is completely different, it will run side by side with VS.NET.
So, all in all, a very good and powerful platform for the programmer, especially since it supports multiple programming languages.
