You can search the forum for C# examples.  Here are a couple that should get you started.

Create invoice using BOI - Sage 100 Personalization, Customization, and Productivity Tools - Sage 100 - Sage City Community

How to read single record with BOI (C#) - Sage 100 Business Object Interface - Sage 100 - Sage City Community

Equivalent of nCopyPurchaseOrderLines for Sales Order? - Sage 100 Distribution, Manufacturing, and Internet Modules - Sage 100 - Sage City Community

You might not always find the exact example that you are looking for but they should give you a good head start.

You should also refer to the online file layouts and object reference for more details.

Sage 100 File Layouts and Object Reference - Sage 100 File Layouts and Object Reference

Once you understand the basics of using the BOI, you can observe how an entry is entered by a user in a particular task in Sage 100, such as Sales Order Invoice Data Entry and observe the order in which fields are populated.

Thanks for update , will check , i am able to create sales document using object matrix dll but only facing problem with invoice.