Prior to Windows XP, an ActiveX control had to be registered on the system before it could be used by an application. This registration creates a few issues among which:

• Registering a control requires administrative rights on a system.
• Registering a control affects multiple applications as the same DLL is shared among all applications using the same version of the control (some developers refer to this issue as the DLL hell.)
• An application that unregisters a control will prevent all other applications from using it.

The solution to these issues is to use side-by-side activation, or registration-free components; a concept that is very similar to what was introduced with .NET.

When side-by-side registration is used, two things happen:

• scvncctrl.dll can be placed in each application's folder and is not shared with other applications.
• The ActiveX control is not registered in the system wide registry but each application acts as if it had its own registered component.

Enabling this feature is straight-forward with Visual Studio 2005 or newer. Simply open the "References" panel, right-click on the control that you are using and set the Isolated property to True. When this is done, Visual Studio generates a manifest file that is similar to what is shown below. Note that the manifest has to be in the same folder as your application.

Sample manifest:

<?xml version="1.0" encoding="utf-8"?>
<assembly xsi:schemaLocation="urn:schemas-microsoft-com:asm.v1 assembly.adaptive.xsd" manifestVersion="1.0" 
          xmlns:asmv1="urn:schemas-microsoft-com:asm.v1" xmlns:asmv2="urn:schemas-microsoft-com:asm.v2" 
          xmlns:asmv3="urn:schemas-microsoft-com:asm.v3" xmlns:dsig="http://www.w3.org/2000/09/xmldsig#" 
          xmlns="urn:schemas-microsoft-com:asm.v1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <assemblyIdentity name="WindowsFormsApplication2.exe" version="1.0.0.0" processorArchitecture="x86" type="win32" />
  <file name="scvncctrl.dll" asmv2:size="3410432">
    <hash xmlns="urn:schemas-microsoft-com:asm.v2">
      <dsig:Transforms>
        <dsig:Transform Algorithm="urn:schemas-microsoft-com:HashTransforms.Identity" />
      </dsig:Transforms>
      <dsig:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
      <dsig:DigestValue>XajYMS77zmmOZpx3OfMe3ByRIqk=</dsig:DigestValue>
    </hash>
    <typelib tlbid="{2864468c-765f-4ef3-b8cf-42666c92b545}" version="1.0" helpdir="" resourceid="0" flags="HASDISKIMAGE" />
    <comClass clsid="{62fa83f7-20ec-4d62-ac86-bab705ee1ccd}" threadingModel="Apartment" tlbid="{2864468c-765f-4ef3-b8cf-42666c92b545}" 
              progid="SmartCode.ViewerX.3" description="SmartCode VNC Viewer Control" />
  </file>
</assembly>