Problem in ComAutomationFactory.CreateObject

I tried to create object using ComAutomationFactory.CreateObject . It is giving following exception

     "Failed to create an object instance for the specified ProgId"

My application is running on OOB and has elevated permission.

if (ComAutomationFactory.IsAvailable && App.Current.HasElevatedP开发者_如何学运维ermissions) {

                dynamic sample = ComAutomationFactory.CreateObject("SampleCom.ComClass");

            }

where SampleCom is a my Com Application created in C#

I use Silverlight 4

Only if the Dll is signed you can Create object using ComAutomationFactory.CreateObject