To ensure the exchange of data between the application Barcode Terminal Hosting and accounting system uses a pair of xml-files InventoryListToTCD.xml and InventoryListFromTCD.xml

File InventoryListToTCD.xml need to record data on goods from accounting system into the data collection terminal. Usually this is the simpliest list of goods stored in the following fields:

• BarCode - bar code have a numeric or alpha-numeric values
• Description - description of goods
• Quantity - quantity of goods in the accounting system
• Price - unit price

We briefly describe step by step how the goods written into the data collection terminal.

• from the accounting system, we must write to the file InventoryListToTCD.xml.
• When the data collection terminal accessed through Web-service to the application BarCode Terminal Hosting for the goods list, Barcode Terminal Hosting will return the contents of InventoryListToTCD.xml into the data collection terminal.

Once we made the stocktaking and entered actual inventory rests into the data collection terminal, our task - to transmit the data to the accounting system. We describe the process of uploading data from the terminal in steps.

1. data collection terminal accesses Barcode Terminal Hosting and send information about the actual inventory rests through the Web-service.
2. Barcode Terminal Hosting writes inventory rests data into the file InventoryFromTCD.xml.
3. accounting system reads the file InventoryListFromTCD.xml and takes into actual balances itself. The data can be loaded into documents of various types. Data can be downloaded into the inventory act (stocktaking), into purchase invoice or sales invoice

File Structure InventoryListFromTCD.xml completely identical to the file InventoryToTCD.xml, only the data they transmit in opposite directions. More details about the data exchange can be read article

Once the system has been developed exchange, but to put it demands absolute universality and the possibility of interfacing with any accounting system, the question of simplifying the programmers who will match records system BarCode Terminal Hosting. The simplest and correct solution - to create OLE-components, ActiveX library that implements the data exchange with the methods of reading and record. This library is called BarCodeHosting.dll and comes together with the application BarCode Terminal Hosting. During installation, the application library located in the Windows\System32 folder and is automatically registered. Describe classes, properties and methods that implement this Library.

1. InventoryItem.A simple class that implements the four properties describing the goods:
   • Properties:
     • BarCode (type String) - bar code in numeric or in alpha numeric form
     • Description (type String) - name of the product
     • Quantity (type Double) - quantity of goods in the accounting system
     • Price (type Double) - unit price
2. Writer- a class that implements a data record in the file InventoryToTCD.xml from your system.
   • Methods:
     • Public Sub OpenWriter (ByVal Path As String) - opens object in writing to the file InventoryListToTCD.xml, which Located on the way to the variable Path
     • Public Sub AddItem (BarCode As String, Description As String, Quantity As Double, Price As Double) - adds to the the list of goods new product with the parameters specified in variables BarCode, Description, Quantity and Price
     • Public Sub WriteData () - writes a list of commodities in file InventoryListToTCD.xml. For re-entry is required reopen the facility to record and add a method OpenWriter Product list.
   • Properties:
     • Subclass Recordset lets you directly access the data for more advanced programming.

   Example of using class Writer (from the sample application).

   1. 'Use BarCodeHosting.dll for write data to InventoryListToTCD.xml file
   2. Dim Writer As New BarCodeHosting.Writer 'create New Writer object
   3. Writer.OpenWriter Me.txtExchangePath.Text 'standby for write data to file
   4. Dim i As Long
   5. For i = 1 To Me.lstDataToTerminal.ListItems.Count 'Read List Items from ListView control and add it to the Writer object
   6.   Writer.AddItem Me.lstDataToTerminal.ListItems(i).Text, Me.lstDataToTerminal.ListItems(i).SubItems(1), Me.lstDataToTerminal.ListItems(i).SubItems(2), Me.lstDataToTerminal.ListItems(i).SubItems(3)
   7. Next i
   8. Writer.WriteData
   9. Set Writer = Nothing
   10. MsgBox "Data was written to file " & Me.txtExchangePath.Text & "\InventoryListToTCD.xml"
3. Reader- a class that implements the data read from the file InventoryFromTCD.xml the accounting system.
   • Methods:
     • Public Sub OpenReader (ByVal Path As String) - reads data from the file InventoryListFromTCD.xml a collection of objects InventoryItem. File InventoryListFromTCD.xml should be in the folder passed in the variable Path
     • Public Sub MoveNext() - allows you to move to the next InventoryItem element in the collection
     • Public Sub MoveFirst() - returns you to the first InventoryItem element in the collection
   • Properties:
     • Public Property RecordCount() As Long - a property that returns the number of loaded commercial records from file InventoryFromTCD.xml
     • Public Property Get Item() As InventoryItem - a reference to the the current item in the collection of trade accounts
     • Public Property Get EOF() As Boolean - returns true if the latter commodity reached a record in the collection
     • Subclass Recordset lets you directly access the data for more advanced programming.

   Example of use. In this example, we read data from file InventoryFromTCD.xml and add them to the cycle in the object lstDataFromTerminal (Class ListView), to view the form.

   1. 'Use BarCodeHosting.dll for read data from InventoryFromTCD.xml file
   2. Dim Reader As New BarCodeHosting.Reader 'create New Reader object
   3. Reader.OpenReader Me.txtExchangePath.Text 'read data to Reader object from file InventoryFromTCD.xml by path was sets in txtExchangePath field
   4. Me.lstDataFromTerminal.ListItems.Clear 'clear ListView
   5. While Not Reader.EOF 'from reader fill the listview in cycle
   6.   Me.lstDataFromTerminal.ListItems.Add , "k" & Me.lstDataFromTerminal.ListItems.Count, Reader.Item.BarCode
   7.   Me.lstDataFromTerminal.ListItems.Item(Me.lstDataFromTerminal.ListItems.Count).SubItems(1) = Reader.Item.Description
   8.   Me.lstDataFromTerminal.ListItems.Item(Me.lstDataFromTerminal.ListItems.Count).SubItems(2) = Reader.Item.Quantity
   9.   Me.lstDataFromTerminal.ListItems.Item(Me.lstDataFromTerminal.ListItems.Count).SubItems(3) = Reader.Item.Price
   10.   Reader.MoveNext
   11. Wend

It must be noted that the Reader and Writer classes are wrappers around ADODB.Recordset class to simplify the programming, because specific and limited tasks.

Library BarCodeHosting.dll can be downloaded in source code with Training example. It is free to explore and modifications to discretion of the developers of systems interfaces.
The library was deliberately implemented in Visual Basic 6, as this development environment currently provides the most simple implementation of the ActiveX DLL, which is very promotes the study and understanding.