Active X DLL in VB.Net

AIM—  To create  an active x  dll in vb.net .

THEORY—

Active x is a technology using which we can create user defined controls .it is not a programming language but rather a set of rules for how applications should share information. an active x can be developed in a variety of languages including c,c++,vb or java .

active x components –it is a general term that consists of three types of projects –

a) active x  dll.

b) active x  exe.

c) active x  controls.

ACTIVE X DLL—a dynamic link library project allows you to create your own type library.

you can create your own library of classes in a project ,compile it to a dll , then reference the dll from other projects to use the functionality (call methods and properties )of the classes your dll contains .the main advantage using a dll is code reuseability ,compile your classes in a dll ,then reference that one dll from as many applications as you like.

ACTIVE X EXE—an activex exe acts in a way like a standard exe, but it needs to be registered to run (like all other activex objects )and like an activex dll it exposes classes that clients can create and use .

there is a big difference between activex dll and exe. the dll is an `in-proc` server , that is it runs in the same memory space . of the main application ,unlike the exe that is a `out-proc ` server and therefor runs in its own memory space (it is basically another application running)for this reason it is much faster to call a dll , because there  is no marshalling  of data between two  processes .

typically activex exe are used to create windows “servers “ that can run locally or remotely in another computer .

ACTIVE X CONTROL –an active x control is also a server application that exposes its functionality through an interface consisting of properties , methods &events

an active x control is similar to java applet .unlike java applets however , active x controls have full access to the windows operating system .this gives them much more power than java applels but with this power comes a certain risk that the applet may damage .software or data on your machine . to control this risk ,microsoft developed a registration system so that browsers can identify and authenticate an active x control before downlpoading it.

active x controls provide the same functionality as dll and axes but are more firmly integrated to the language and they have a visible interface .on the other hand active x dll and activex exe are written code consisting of classes &methods.

  PROCEDURE—

1) open visual basic ide. create a new project of type class          library giving it a suitable name .

2) write the necessary code and create classes for the project.

3) save the project & close it.

4) create a new project(windows application).

5) add the previousp roject as a reference to the new project.

6) use the objects oftype classlibrary.class in your project.

1) display various types of gauges and indicators.

2) display data in grids .

3) send and receive faxes.

4) play audio display vidieo.

5) scan bar codes.

6) display calenders.

CONCLUSION—we  have  successfully created an active x dll  application and is working fine,showing all the methods and properties for the object variables.