Advanced Dotnet Tutorial: Writing an ActiveX control in C#

An ActiveX control is an object that supports a customizable programmatic interface. Using the methods, events and properties exposed by the control, web developers can automate their web pages to give the functionality which is equivalent to that of a desktop application.

Introduction

As web application developers, we want to give our users a highly functional application. We want to provide our users with functionality like printing streams, local socket programming ,local threading, cross domain scripting etc., but as we know that due to the disconnected architecture of the Internet and security restrictions of any standard browser, this task becomes difficult. That’s when the ActiveX comes to the rescue.

This is mostly for webapplications where the users would not be apprehensive about doing a one time installation of the component. Also, in an intranet application these components can be a big boost to the functionality of the application.

Writing ActiveX Class in C#

We will first write an interface called ASignatures which holds the signatures of the methods and properties. These methods and properties can then be accessed via JavaScript at the browser level. By default all members of aninterface are abstract and public.

The main ActiveX class AClass will inherit from this interface. Above the mainActiveX class we will mention the ClassInterfaceType as AutoDual. This will indicate the type of the interfacegenerated for the main class which will automatically be generated and exposed to the COM. Normally AutoDual is not recommended because it has some versioning limitations.

We will use the ClassIntrefaceType as AutoDual because the purpose of this code is instructional. In the main class we will write two methods FName(), and SName() and one property Age. In our example we will return the basic datatypes but this can be implemented for complex datatypestoo.

using System;
using System.Runtime.InteropServices;
namespace ANamespace
{
 
public interface ASignatures
{
string FName();
string SName();
int Age { get;} 
}
 
[ClassInterface(ClassInterfaceType.AutoDual)]
public class AClass :ASignatures
{
public string FName()
{
return "Imran";
}
public string SName()
{
return "Nathani";
}
public int Age
{
get { return 24; }
}
}
}