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hi
i'm workin on a project using linear barcodes to automatically identify individual trains and rolling stock as they pass by the barcode reader.
can i get help on how i can use VB2010 to write a file containing engine information and rolling stock information that i can load into my code so t that as the barcode is read i can display the appropriate information of the windows application i'm building please help!!
The most logical option would be to use a database. You would have one or more tables with the appropriate columns to store the data you need. When you read a barcode you query the database for the data related to that value and display it as desired. There is tons of information on the web about creating data-driven applications so there's no need for us to repeat the same stuff yet again. There are some links in my signature that you might find useful, particularly the Data Walkthroughs and Videos.
Not sure that a database is necessary here. A CSV file (or similar) would allow for easy editing outside of the application, and not require building an interface inside the application to manage the data.
What you would need to do, however, is read the data into a data structure that allows for retrieving a value by specifying a key.
In other words:
- You'll need a class to represent the data for a single engine/stock (this should be able to represent either - if you do need slightly different details, it is possible to create two different classes but this would require a few additional steps so I'll go the less complex route for now).
- You'll need an 'initialisation' routine in your application that can:
- Create an instance of a Dictionary
- Read the data file line by line
- Parse each line and create an instance of the data class with the information from that line of data
- Add each of those instances to the dictionary instance
- When you read a barcode, use the data as the key into the dictionary instance to retrieve the full information from the dictionary
thanks i have decided to use the database to store the trains info, i used sql to build the tables and am using LINQ to SQL to load the tables my code.Quote:
Originally Posted by jmcilhinney
i am facing a problem right now please help. i am trying to display the row of data that corresponds to the barcode i am reading to display in a datagridview table but i am not getting anything to show. here is my code could you please point me in the right direction please.
Public Class Form1
Dim s As String = ""
Dim ctx As TrainsInfoDataContext
Private Function TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles Brcd.KeyPress
If Asc(e.KeyChar) = 13 Then
Brcd.Text = (s + vbCrLf)
s = ""
Else
s = s + e.KeyChar
End If
Return s
End Function
Private Sub DataGridView1_CellContentClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick
ctx.Log = Console.Out
Dim first_train = From Engine In ctx.Train_Engines
Where Engine.Serial_Number = Function TextBox1_KeyPress
End Sub
End Class
I think you've misunderstood how the event-driven model of Windows Forms applications work. When the barcode reader reads a barcode, it simply types the text of the barcode followed by the Return key. So you've presumably set it up so that the TextBox has keyboard focus, then when a barcode is read, the TextBox is typed into. Each time a 'key' is 'pressed' by the barcode reader, the KeyPress event is fired - I'm not entirely sure
You appear to be thinking that you 'pull' the keyboard presses from some kind of buffer when you call the event handler from within the DGV's CellContentClick event handler?
If I were you, I would start by writing a method that takes an identifier string as an argument and to start with maybe just adds it to a listbox:
vbnet Code:
Now we can look at that KeyPress event handler. We're looking for the Return key being pressed, to indicate the end of the barcode reader's input. The normal way of doing this is to use the KeyDown event instead. That gives you the KeyCode property that is an enumeration of the keys on a keyboard and is a slightly better fit:
vbnet Code:
Remember that the TextBox has been typed into, so the preceeding input from the barcode reader is sitting in the TextBox. We can simply read the Text property, no need to handle each keypress and store in a string buffer. So what to do with our identifier? Pass it to the method that will process it. The only other thing we need to do is clear the TextBox so that we don't have the preceeding identifiers still in the TextBox when the barcode reader starts typing the next identifier it sees:
vbnet Code:
thanks alot mate, but i have a few question i would like u to help me with. firstly is a good idea to try and diplay the data from my database using the DGV?? cos when i connected the DGV to my database directly it just showed all the data in the database at the same time but i want to query the data corresponding to the read barcode and display the rows one at a time in real time.
secondly i tried getting the read barcode and using it in another subroutine , i tried calling it with the ProcessTrainIdentifier(TextBox.Text) but it says there is no value to return.
sorry i'm a bit of a blockhead on this coding and thanks for the help
I wouldn't go down the route of the DGV. As you've seen, it is designed to display a grid of data. I would simply stick to some labels/read-only textboxes to hold each field.
As to your second issue, I wonder how you're trying to call the ProcessTrainIdentifier sub? That is not designed to return anything. With the code I posted that sub is executed everytime an engine's barcode is read, so it should retrieve the train details from the database and then display them. I'd expect it to look something like this when you're done (you'll need to correct the TrainInfo type name to whatever your type is called):
vbnet Code:
Obviously, that calls for two new methods you need to write:
vbnet Code:
[snip]
hi mate i tried this but when i'm running it, once i scan a barcode it throws an errorr and an unhandled exception . and p.s in the LINQ TO SQL how will i use the where to point to the location to read the barcode?? thanks.......
Public Class Form1
Dim s As String = ""
Dim ctx As TrainsInfoDataContext
'Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles Brcd.KeyPress
' If Asc(e.KeyChar) = 13 Then
' TextBox1.Text = (s + vbCrLf)
' s = ""
'Else
' s = s + e.KeyChar
'End If
'End Sub
'Private Sub ProcessTrainIdentifier(ByVal identifier As String)
' For now, just log that we saw an identifier
' ListBox1.Items.Add(String.Format("Saw identifier {0} at {1}", identifier, DateTime.Now))
'End Sub
Private Sub TextBox1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
If e.KeyCode = Keys.Return Then
ProcessTrainIdentifier(TextBox1.Text)
TextBox1.Clear()
End If
End Sub
Private Sub ProcessTrainIdentifier(ByVal identifier As String)
Dim trainInfo = GetTrainInfo(identifier)
DisplayTrainInfo(trainInfo)
End Sub
Private Function GetTrainInfo(ByVal identifier As String) As TrainsInfoDataContext
' LINQ To SQL code goes here
Dim engines = From trn In ctx.Train_Engines
Where trn.Serial_Number = "1101" Or "1102"
Select trn
For Each trn In engines
ListBox1.Items.Add(trn.Serial_Number & vbTab & trn.Running_Number & vbTab & trn.Manufacturer & vbTab &
trn.Engine_Type & vbTab & trn.Purpose & vbTab & trn.Class & vbTab & trn.Group & vbTab & trn.Weight)
Next
Return engines
End Function
Private Sub DisplayTrainInfo(ByVal trainInfo As TrainsInfoDataContext)
' Write the data in trainInfo to the UI
End Sub
End Class
I think you've misunderstood. You don't need to read the barcode in the LINQ to SQL code - the barcode has already been read, and it is sitting in the identifier variable. The GetTrainInfo method is not supposed to return the TrainsInfoDataContext, it is supposed to use the TrainsInfoDataContext to grab the TrainsInfo object for the identifier.
Each time a barcode is read, the following happens:
TextBox1 is populated with the barcode data.
ProcessTrainIdentifier is called with the contents of the TextBox in the identifier variable
GetTrainInfo is called, passing that identifier through.
GetTrainInfo uses the identifier to return a record representing a single train
DisplayTrainInfo is called with the returned traininfo value
DisplayTrainInfo writes values from the traininfo object on to the UI.
ok i think i get where u're coming from cheers, this is what i've modified so far, hope the first parts make sense . the DisplayTraininfo though is giving me a tough time on how to use the traininfo to display the tables that have been quired y the identifier
Private Sub TextBox1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
If e.KeyCode = Keys.Return Then
ProcessTrainIdentifier(TextBox1.Text)
TextBox1.Clear()
End If
End Sub
Private Sub ProcessTrainIdentifier(ByVal identifier As String)
Dim trainInfo = GetTrainInfo(identifier)
DisplayTrainInfo(trainInfo)
End Sub
Private Function GetTrainInfo(ByVal identifier As String) As TrainsInfoDataContext
' LINQ To SQL code goes here
Dim engines = From trn In ctx.Train_Engines
Where trn.Serial_Number = identifier
Select trn
Dim rolling_stock = From rollstck In ctx.Rolling_Stocks
Where rollstck.Serial_Number = identifier
Select rollstck
End Function
Private Sub DisplayTrainInfo(ByVal trainInfo As TrainsInfoDataContext)
' Write the data in trainInfo to the UI
' Dim dsply_Eng As String
'Dim dsply_Rollstock As String
EngInfoLbl = trainInfo.Train_Engines.ToString((ctx.Train_Engines.Serial_Number & vbTab & trn.Running_Number & vbTab & trn.Manufacturer & vbTab &
trn.Engine_Type & vbTab & trn.Purpose & vbTab & trn.Class & vbTab & trn.Group & vbTab & trn.Weight)
End Sub
hi mate, i've worked through it again and it seems not to throw in any errors anymore but it does not show any data when i read the barcode??
Public Class Form1
Dim s As String = ""
Dim ctx As New TrainsInfoDataContext
'Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles Brcd.KeyPress
' If Asc(e.KeyChar) = 13 Then
' TextBox1.Text = (s + vbCrLf)
' s = ""
'Else
' s = s + e.KeyChar
'End If
'End Sub
'Private Sub ProcessTrainIdentifier(ByVal identifier As String)
' For now, just log that we saw an identifier
' ListBox1.Items.Add(String.Format("Saw identifier {0} at {1}", identifier, DateTime.Now))
'End Sub
Private Sub Brcs_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Brcd.KeyDown
If e.KeyCode = Keys.Return Then
ProcessTrainIdentifier(Brcd.Text)
Brcd.Clear()
End If
End Sub
Private Sub ProcessTrainIdentifier(ByVal identifier As String)
Dim trainInfo = GetTrainInfo(identifier)
'DisplayTrainInfo(trainInfo)
' DisplayTrainInfo(trainInfo)
End Sub
Private Function GetTrainInfo(ByVal identifier As String) As String
' LINQ To SQL code goes here
Dim engines = From trn In ctx.Train_Engines
Where trn.Serial_Number Like identifier
Select trn
Me.Train_EngineBindingSource.DataSource = engines
'Dim rolling_stock = From rollstck In ctx.Rolling_Stocks
'Where(RollStck.Serial_Number Like identifier)
' Select RollStck
End Function
Private Sub DisplayTrainInfo(ByVal trainInfo As TrainsInfoDataContext)
' Write the data in trainInfo to the UI
End Sub
thanks i understand it now, i have got the code working , reading the barcodes ans displaying the appropriate data in a DGV, but a problem has developed in that it only shows the engine information but when i scan a rolling stock or cart it does not show it.... here is the code pls if u can see where the cause of this is pls help me point it out thanks.Quote:
Originally Posted by Evil_Giraffe
Public Class Form1
Dim s As String = ""
Dim ctx As New TrainsInfoDataContext
Private Sub Brcs_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Brcd.KeyDown
If e.KeyCode = Keys.Return Then
ProcessTrainIdentifier(Brcd.Text)
Brcd.Clear()
End If
End Sub
Private Sub ProcessTrainIdentifier(ByVal identifier As String)
Dim trainInfo = GetTrainInfo(identifier)
Dim rollinfo = GetRollingStockInfo(identifier)
'DisplayTrainInfo(trainInfo)
' DisplayTrainInfo(trainInfo)
End Sub
Private Function GetTrainInfo(ByVal identifier As String) As DataGridView
' LINQ To SQL code for engine
Dim engines = From trn In ctx.Train_Engines
Where (trn.Serial_Number = identifier)
Select trn
Me.Train_EngineBindingSource.DataSource = engines
End Function
Private Function GetRollingStockInfo(ByVal identifier As String) As DataGridView
' LINQ TO SQL code for rolling stock
Dim rolling = From rollstck In ctx.Rolling_Stocks
Where (rollstck.Serial_Number Like identifier)
Select rollstck
Me.Rolling_StockBindingSource.DataSource = rolling
End Function
End Class
i was trying to compare succesive barcodes as they are read cos i put two barcodes on each train and cart so i can know the direction of travel..
i used this piece of code to do it but its not workin pls can u give me an input??
Private Sub TrainDirection(ByVal identifier As String)
Dim direc() As String = {"identifier", "idnetifier++"}
Dim direction As String
If identifier < identifier++ then
TextBox1.Text = "Forward"
Else if identifier > identifier ++ then
TextBox1.Text = "Reverse"
End If
secondly pls can u give me an idea on how i can log the train informations as they are read into another database so i can have a history of all the trains that have passed along with timestamps for each thanks alot
Okay, this ups the complexity of your problem a degree. Now you need to separate the concept of 'a barcode was read' from the concept of 'an engine/piece of stock has gone past the sensor' - because now you have two barcode events for each engine.Quote:
Originally Posted by Eng_Mc
I think my initial approach would be to be able to look up the train info from either barcode, and if it's for a record with a 'front' and 'back' identifier, you can assume this is the first one you've seen and therefore know the direction of travel, and then indicate that if the next seen barcode is the 'other' code for this engine then ignore it.
Well, you have code that is fired whenever a barcode is read, you can use Date.Now to get a timestamp, then it's a simple case of inserting into an appropriate table in the database, surely?Quote:
Originally Posted by Eng_Mc
okay, i wrote this code to determine the train direction, it works... but i often get reverse inter of forward and then it skips back to the correct direction. i don't know why it does that?? is there anything i can add to the code to full proof it againt such mistakes ocurring??Quote:
Originally Posted by Evil_Giraffe
Private Sub Brcs_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Brcd.KeyDown
If e.KeyCode = Keys.Return Then
ProcessTrainIdentifier(Brcd.Text)
barcodes.Add(Brcd.Text)
Brcd.Clear()
End If
If barcodes.Count = 2 Then
CompareBarcodes(barcodes(0), barcodes(1))
barcodes.Clear()
End If
End Sub
'this function receives two succesive barcode values converts them to integer values and compares the values to determine direction of travel
Private Function CompareBarcodes(ByVal stringA As Int64, ByVal stringB As Int64)
If Convert.ToInt64(stringA) < Convert.ToInt64(stringB) Then
TextBox1.Text = "Forward"
ElseIf Convert.ToInt64(stringA) > Convert.ToInt64(stringB) Then
TextBox1.Text = "Reverse"
Else
TextBox1.Text = ""
End If
End Function
[/QUOTE]Well, you have code that is fired whenever a barcode is read, you can use Date.Now to get a timestamp, then it's a simple case of inserting into an appropriate table in the database, surely?[/QUOTE]
okay yeah, but the address i could pass for the add is what is gettin me confused .... see the code i've written but i'm stuck here not knowing how to pass the data .....
the first code reads the barcode and shows the data :
Private Function GetTrainInfo(ByVal identifier As String) As DataGridView
' LINQ To SQL code for trains
Dim engines = From trn In ctx.Trainsses
Where (trn.Serial_Number = identifier)
Select trn
Me.TrainssBindingSource.DataSource = engines
Return TrainssDataGridView
End Function
this second code is in another form i created and used a button to open it from the first form so that this table would be in the new form. but i am lost for code on how to populate the table with the data from the first table as it is being read....
Public Class TrainLog
Dim ctx As New TrainsInfoDataContext
Private Sub TrainLog_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim P As New Train_Log
P.Date_and_Time = Today()
P.Serial_Number =
P.Running_Number =
P.Manufacturer =
P.Engine____Cart_Type =
P.Purpose =
P.Load_Size =
P.Class =
P.Group =
P.Weight =
Me.Train_LogBindingSource.DataSource = P
End Sub
End Class