>... in my case, I need to add third party code to my CSU package. ...
In my above examples I described all the steps I made to produce the MyClassLibrary.dll which playis the role of the "third party code" - that essentially a DLL produced completely outside of the SDK.
>... The third party code is in Retail SDK format. ...
Can you please be more specific and describe what you meant by saying "Retail SDK format" exactly and how that differs from the example I outlined in my previous message?
>... and add all the code in format of Commerce SDK. ...
What do you mean exactly by saying the "format of Commerce SDK" ?
>... When I go for build, it created package but there is no dlls in ext folder. ...
Not sure I understand what you meant exactly - are you saying you complied the CommerceRuntime project and as a result you are not seeing ANY DLLs in the EXT folder at all ? If the EXT folder contained the dll prior the modifications you made but the EXT folder is empty after the modifications then, most likely, there were build warnings/errors - did you see any?
>... I also tried the above method but it still doesn't working. ....
When you say "above" - did you mean the one I outlined in my previous message? If so - please be very specific as I did and provide fully reproducible steps so I could try them out on my box, so far you are not providing enough details to help you further.