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This article is about how VB.NET implements bar code programming. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Bar code technology is widely used in various industries. You can pick up a book or a bag of potato chips and find them on the outer packaging. Using a bar code reader, you can identify these black and white vertical lines with different thickness and convert them into specific values, and return this value to the computer for processing. In this way, with bar code technology, people can easily obtain information about the commodity, such as commodity name, specification, price, etc., because each commodity has its own bar code. the bar code computer (terminal, server) can quickly return to the user, read the agreed goods from the database, and the information makes the management of sales, purchase, inventory and so on more efficient. It also has a certain inhibitory effect on preventing fake and shoddy products.

There are many ways of bar code coding, and different industries and different national standards are not the same. The bar code expresses its value by the thickness of the line. As for the interface generally there are many ways, such as keyboard port, serial port. General sensing devices are either mask-type or pen-type.

The above cage talks about some knowledge about bar codes, which can help you better read the following more in-depth content. Bar code related concepts first stop here, followed by detailed and specific programming methods.

I. Reading in VB.NET bar code programming

Friends who have used the keyboard-style bar code tool will know that it is like "pressing a number on a disk" without any programming or processing. But if you are using another interface, you may have to write communication code for the device. Here is a simple 25-pin barcode reader communication code.

Option Explicit Dim sData As String Private Sub Form_Load () With MSComm1. CommPort = 3'is set to COM3, depending on the trial run of the system, you can provide a Combox for users to choose. .PortOpen = True 'Open communication port End With End Sub Private Sub MSComm1_OnComm () Dim EndPos As Integer Select Case MSComm1.CommEvent Case comEvReceive' when data is transmitted, sData = sData & Trim (MSComm1.Input)'to retrieve the carriage return. Usually, the card reader returns a carriage return at the end of each set of data as the Terminator EndPos = InStr (1, sData). Chr (13) If EndPos = 0 Then'if it's not over, keep trying to Else 'finish reading a group. LblBarCode.Caption = sData 'display a set of barcodes With lstBarCode. AddItem Mid (sData, 1, EndPos-1)' add a set of barcodes to the list End With sData = "'empty End If End Select End Sub Private Sub cmdEnd_Click () MSComm1.PortOpen = False' close port End End Sub

II. Generation in VB.NET bar code programming

Do you find it easy to read the above code about bar code reading? Yes, programming on VB is not difficult at all. The following code about bar code generation is also easy to understand. You can easily print out 11 different standard bar codes by using a BarCode control that comes with OFFICE, which is enough to meet our requirements. I think of an article in a book on my shelf that wrote a bar code printing program in Turbo C. at that time, I didn't know that I had read it for n days and typed for n hours, but the result was not satisfactory.) now I am much happier. After talking nonsense, we have to get back to business. Let's take a look at the code generated by the bar code and related instructions.

The source code mainly consists of two forms (frmMain main form and frmOption barcode setting form) and two modules

(modGetScreen.bas, SysDLG32.bas) Considering the length, only some of the more critical codes are listed here.

Create a new standard project, add a barcode widget named (Microsoft Access BarCode Control9), add a barcode control to the window, and rename the window to frmMain, as shown. As there are many controls, it is inconvenient to elaborate here. Please refer to the source code for details.

The module modGetScreen.bas code is as follows:

Option Explicit

Declare the API functions of BitBlt, GetDesktopWindow, GetWindowDC and ReleaseDC

Public RegUser As Boolean Sub GetObjImage1 (Obj As Object, OwnerForm As PictureBox, Picture1 As PictureBox) 'hDC Dim hWndDesk As Long Dim hDCDesk As Long' region expression variable Dim x As Long Dim y As Long Dim w As Long Dim h As Long x = Obj.Left Screen.TwipsPerPixelX y = Obj.Top Screen.TwipsPerPixelY w = Obj.Width Screen.TwipsPerPixelX h = Obj.Height Screen.TwipsPerPixelY hDCDesk = OwnerForm.hdc 'take out the image Call BitBlt (Picture1.hdc, 0,0, w, h HDCDesk, x, y, vbSrcCopy) Call ReleaseDC (hWndDesk, hDCDesk) End Sub

The frmMain.frm code of the main form is as follows:

Private Sub cmdPrint_Click () 'generate barcode image Dim r As Long, i As Integer, t As String,cfile As String' temporary variable t = BarCode For i = 0 To Val (Times)-1 BarCode1.Value = BarCode + I DoEvents Picture1.Refresh GetObjImage1 BarCode1, Conel, Picture1 If RegUser = False Then 'add MASK tag Picture1.PaintPicture Picture2.Picture if not registered 300 End If If Dir (SavePath, vbDirectory) = "" Then MkDir SavePath SavePath = SavePath & IIf (Right (SavePath, 1) ",",") cfile = SavePath & BarCode1.Value &" .bmp "SavePicture Picture1.Image, cfile 'saves the bar code as an image file for printing Next BarCode = t End Sub

The barcode setting form frmOption.frm code is as follows:

Option Explicit

'Bar code setting module

Private Sub cboBig_Click () BarCode1.Style = cboBig.ListIndex 'change standard End Sub Private Sub cboDirection_Click () BarCode1.Direction = cboDirection.ListIndex' change direction End Sub Private Sub cboLine_Click () BarCode1.LineWeight = cboLine.ListIndex 'change linewidth End Sub Private Sub cboSmall_Click () BarCode1.SubStyle = cboSmall.ListIndex' change style End Sub Private Sub Check1_Click () BarCode1.ShowData = Check1.Value 'whether to display data End Sub Private Sub cmdChange_Click ()' setting length, Wide size BarWidth = BarCode1.Height BarHeight = BarCode1.Width cmdRefresh_Click End Sub Private Sub cmdOK_Click () 'transmits barcode settings to the main interface With frmMain.BarCode1 .LineWeight = BarCode1.LineWeight .style = BarCode1.Style .SubStyle = BarCode1.SubStyle .Direction = BarCode1.Direction .width = BarCode1.Width .Height = BarCode1.Height .showData = BarCode1.ShowData Me.Hide End With With frmMain .Picture1.Width = .BarCode1.Width .Picture1.Height = .BarCode1.Height .Conel.Width = .BarCode1.Width .Conel.Height = .BarCode1.Height End With End Sub Private Sub cmdRefresh_Click () BarCode1.Width = BarWidth BarCode1.Height = BarHeight End Sub Private Sub Form_Load () LoadBarInfo BarWidth = BarCode1.Width BarHeight = BarCode1.Height End Sub Sub LoadBarInfo () 'initialization Option LoadBigClass cboBig LoadSmallClass cboSmall LoadLineSize cboLine LoadDirection cboDirection End Sub Sub LoadBigClass (cbo As ComboBox) 'barcode standard With cbo .AddItem "UPC-A" .AddItem "UPC-E" .Addit em "EAN-13" .AddItem "EAN-8" .AddItem "Case Code" .AddItem "Codabar (NW-T)" .AddItem "Code-39" .AddItem "Code-128" .AddItem "U. S. Postnet ".AddItem" Postal FIM ".AddItem" JP Post ".ListIndex = 2 End With End Sub Sub LoadSmallClass (cbo As ComboBox) 'barcode style With cbo .AddItem" .AddItem "2-Digit Supplement" .Ad dItem "5-Digit Supplement" .AddItem "POS Case Code" .ListIndex = 0 End With End Sub

When writing database applications, many people want to add bar code functions to enhance work efficiency, especially applications with large traffic, such as sales management and library management. however, because it is difficult to master the bar code technology, who is marked more, and the technology in the past, many people are prohibitive.

Thank you for reading! This is the end of the article on "how to realize bar code programming in VB.NET". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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