To understand VB.NET, we must first understand the .NET platform.
.NET Framework: a set of approximately 3500 classes.
These classes are divided into namespaces that group similar classes together.
For organization, each class belongs to only one namespace.
Most classes are lumped into a name space called System
System.Data contains classes used for accessing data in a DB
System.XML contains classes used for reading/writing XML
System.Windows.Forms contains classed used for
System.Net contains classes for communicating over the network.
Essentially MS performed a massive re-organization of all the classes, no longer leaving methods or functions without clearly belonging to a specific class. For example, note the difference between Messagebox() in VB6.0 and Messagebox.Show() in VB.NET (to be discussed later).
Visual Studio.NET is the next version of IDE from MS.
Note: VS.NET does require at least double its system requirements to function feasibly.
Note: VS.NET can be installed on the same machine as VS 6.0. Many have warned against it, yet personal experience has proven otherwise.
VS.NET comes standard with VB.NET, C# (C-Sharp), and VC++.
VS.NET supports more than 20 languages.
All languages compile to .EXE and .DLLs containing Common Intermediate Language (CIL or IL), not machine native code. C++ is the only exception offering an option to compile to machine native code.
These CIL executables then run in the Common Language Runtime (CLR) using a Just-in-Time (JIT) compiler. Note the similarity of .NET to JAVA and JVM.
The JIT compiler dynamically converts the IL to machine native code during execution, and caches the native code for subsequent use.
Advantages of CLR
The JIT allows code to run in a protected environment as managed code. The protected environment polices each application to run in its own memory segment. This prevents a developer from shooting himself in the foot, but it also limits control.
Using a JIT allows the IL code to be hardware independent. As long as the .NET framework is installed, the IL code can be executed.
The CLR also allows for enforcement of code access security.
Verification of type safety.
Access to Metadata (enhanced Type Information)
Support for developer services (profiling, debugging)
Interoperation between managed code, COM objects, pre-existing DLLs (unmanaged code and data).
.NET components can access COM components.
COM components can access .NET components by registering the .Net assembly using the regasm.exe utility.
.NET provides a unified Programming Model
Then: VB for RAD, VC++ for MFC/ATL, ASP for code embedded web pages
Now: Any language to handle any .NET functionality.
.NET Framework supports Web Standards
WSDL for Web Services
The IL can be modified using Intermediate Language Dis-assembler (ILDASM). ILDASM is a tool used to properly display IL in a human readable format. A developer can then add remove code as needed for fine tuning. Many developers speak highly of this method for fine tuning code.
Visual Studio.Net vs. Visual Studio 6.0
Syntax of event handling methods:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
In VS.Net CTRL-ESC opens inteli-sense for easy searching of methods
With VB6.0, project files were very simple:
.CLS / .FRM / .RES
File structure in .NET varies greatly from VB6.0 file structure.
Note: For a tree diagram of the file structure, enter the following in a DOS prompt.
C:\>Tree C:\VBPrograms\WindowsApplication1 /F /A
Both .EXE are executable, pending the user has .NET framework installed.
Use of “Imports System.IO” imports the System.IO. This is similar to the With block code.
Downloading code is also available.
No need to register components.
Can run multiple component versions simultaneously.