How to Integrate Sales Order from Other System to SAP

In this example, I am going to integrate Sales Transaction from POS System to SAP Business One. To do this, I have separated some parts as below
I. Connection
 a. SAP Connection : Connection is the first require that you need to define. Without connection, you can do nothing. the connection contain some information such as SAP Server Address, System Landscape Address, Database Name, Database User, SAP User and SAP user password ( for SAP User, normally I use user manager for integration ).
 b. POS Connection: To get data from POS database, u need to define connection to POS System. There are alot of ways to get data from SQL database such as SQLDataAdapter, Entity, Linq...In this example, I am going to use Linq to get data from POS Database and integrate to SAP.
II. SAP Components
  SAP components, I refer to what object are you going to integrate to SAP such as Item Master Data, Business Partner Master Data, Sales Order, Purchase Order,..... you need to define which object? In this example, I am going to integrate Data from POS to AR Invoice.
III. Let's do it.
 a. Variable Declaration
   a.1 SAPbobsCOM.Company oCompany;
   a.2 SAPbobsCOM.Documents AR = null;
   a.3 POSDataContext db = null;
 b. Create Function
   b1. ConnecttoSAP: you need to set propertied as below
       db=new POSDataContext("Data Source=192.168.0.1;Initial Catalog=POSDB;Persist Security Info=True;User ID=sa;Password=1111");
       oCompany = new Company();
       oCompany.Server = "192.168.0.1"; SAP Server Name
       oCompany.LicenseServer = "192.168.0.1"; SAP System Landscape
       oCompany.CompanyDB = "SBODEMOAU"; SAP Database Name
       oCompany.DbServerType =  BoDataServerTypes.dst_MSSQL2014; (It is your SQL Version)
       oCompany.DbUserName = "sa";
       oCompany.DbPassword = "1111"; SQL sa Password
       oCompany.UserName = "manager"; SAP User ( manager )
       oCompany.Password = "1111"; // manager password
       int i = oCompany.Connect();
       Noted: If i=0, mean you connect to SAP successfully
   b.2. Integrate Data to AR 
       foreach (Invoice inv in db.Invoices.Where(x => x.sync==null))//loop that get data from POS DB
      {
             AR = (SAPbobsCOM.Documents)oCompany.GetBusinessObject(BoObjectTypes.oInvoices);
          ////BoObjectTypes.oInvoices = AR Invoice, you can define other by just changing this value
          AR.CardCode = inv.bpcode;
          AR.CardName = inv.bpname;
          AR.DocDate = inv.docdate.Value; 
          foreach (invoiceitem item in inv.invoiceitems)//Loop to detail transaction detail item
          {
               AR.Lines.ItemCode = item.itemcode;
               AR.Lines.ItemDescription = item.itemname;
               AR.Lines.Quantity = (double)item.quantity.Value;
               AR.Lines.Price = (double)item.unitprice; 
               AR.Lines.DiscountPercent = (double)item.discountpercent.Value; 
               AR.Lines.WarehouseCode = item.whscode;
               AR.Lines.Add();
          }
         int haserror=AR.Add()         {
         Noted: If haserror==0 mean that this transaction already added to AR Invoice in SAP
        }

If you cannot integrate and got some error, you can paste your error in comment and I will help to solve for you. Have a great day!!!