For AutoCAD customization we are working on both COM API & .NET API
Some of the difference I knew it but I want to know more so please
can any one tell me the difference(5 or 6) as much as possible between COM API & .NET API ?
If possilbe then please also post the Pros & Cons of both API.
Honestly, there should be no selection process like this... The COM API is totally available from .NET, your selection should straight away be ".NET"
i recommend you use VB.NET, that way existing VBA code can be easily ported to run in VB.NET.
The COM API has functionality that the .NET API does not, and vice versa. You should embrace COM from your master VB.NET project workspace.
The main downside to using the COM API is that doing so ties your code to a specific processor type - in otherwords, you have to build specific x86 and x64 modules; whereas if you write pure .NET (with no references to COM) your modules are platform agnostic.
If you have any questions about what tools or apis to use, you should read my blog on "The Right tools for the job" http://adndevblog.typepad.com/autocad/2012/07/the-right-tools-for-the-job-autocad-part-1.html