How to make an order of sale of epicor 10 from a visual studio web application

I have managed to make the connection of epicor 10 with visual study using the ice.core.session dll and Erp.common.contractinterfaces initiating session with epicor users from my visual studio web application, save I need to make a new sales order but I do not know what dll to use for it

This is a code review category you are not posting any code to review. Moving to the E10 category

Run a trace on Epicor and it will tell you which BO to use which will in turn tell you which DLL to use use. On E10 it is highly recommended you use REST from an external application instead of DLLs.
DLLs are version dependent and very heavy compatibly speaking. IF you don’t want to use REST then use the WCF services again DLLs should be a last resort IMO.