This has got to be one of the most frustratingly stupid bugs I have ever encountered, and I just want to see if anybody else has run into this before.
Here's the deal. I have a TextBox in a Windows Forms application in VB 2008 (.NET 3.5) where a user can key an estimate amount. I am allowing them to key dollars and cents, and I want to round to the nearest dollar. The original code had the rounding down when the data was written back to a table, and that worked fine - I have this code in a "Save" routine that fires when the user moves to a different screen or record:
Dim est As Decimal : Decimal.TryParse(txtEstimateAmount.Text.Trim, est)
Dim estimatedAmount As Integer = Math.Round(est)
I decided that it might be nice to actually do the rounding as soon as they leave the field instead, so they're not surprised when they reload the screen and find that 1822.60 is now 1823. So I took the exact same code and added it to the TextBox.Leave event handler. And the weirdest thing happened: instead of the variable est being populated with 1822.60 after the parse, it gets set to -1! What the...?
Debugging the handler shows that the value goes into the parser correctly, and if I do the parsing manually via the Immediate window, it parses correctly, but when I let the code do it, it invariably gets set to -1. What's even weirder is that any number gets parsed as -1, not just decimals, and any non-number gets parsed as 0 (which is correct).
Has anybody else ever run into this before? I tried moving the code to the TextBox.LostFocus event instead, but with the same results. I have no idea what in the heck is going on, and obviously there are workarounds galore for this, but it just makes no sense whatsoever.
EDIT: Here's the full event handler (current behavior for which is to put -1 in the TextBox):
Private Sub txtEstimateAmount_Leave(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtEstimateAmount.Leave
' Take any dollars-and-cents amount and round to the nearest dollar
Dim est As Decimal
est = Decimal.TryParse(txtEstimateAmount.Text.Trim, est)
txtEstimateAmount.Text = If(est <> 0, Math.Round(est).ToString(), String.Empty)
End Sub
First off, you really need to do this with a Validating event handler so that you can catch junk and avoid ignoring the return value of TryParse. Like this:
Private Sub TextBox1_Validating(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles TextBox1.Validating
Dim est As Decimal
If TextBox1.Text.Length = 0 then Exit Sub '' optional
If Not Decimal.TryParse(TextBox1.Text.Trim, est) Then
e.Cancel = True
TextBox1.SelectAll()
Else
TextBox1.Text = est.ToString("N0")
End If
End Sub
Explaining -1 is difficult. TryParse normally writes 0 if it cannot parse the text. Watch out for changing the UI thread's CurrentCulture property. And any changes made to the format settings in Control Panel + Region and Language applet.
I don't think the code you've posted is the code you're running. What is happening is:
Dim est As Decimal = Decimal.TryParse(txtEstimateAmount.Text.Trim, est)
Dim estimatedAmount As Integer = Math.Round(est)
I would do a clean and a rebuild or try rewriting it in a different format, maybe with a boolean to get the result of the tryparse.
EDIT now that I've seen your actual code. You are indeed putting the true/false from the tryparse result into the est decimal. Delete the est=. Est gets loaded because it is passed by reference into tryparse.
Related
I'm trying to format two specific text boxes to show up as Sq. ft. (txt.Squareft.Text) and US currency (txtTotalprice.Text) after a calculation has been made in Visual Studio 2019 as a Windows Form Application and using visual basic code. I am using .NET framework v4.7.2 and utilizing Windows 10. The way it runs now, the numbers that show up in the textboxes are just numbers without the added Sq. ft. at the end and no currency formatting. I will also add that I am very new to VB and programming in general. Any help or suggestions?
Option Explicit On
Option Infer Off
Public Class Form1
Private Sub btnCalculate_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click
'Variables
Dim decTotalprice As Decimal
Dim decLength As Decimal
Dim decWidth As Decimal
Dim decPrice As Decimal
Dim decSquareft As Decimal
Decimal.TryParse(txtLength.Text, decLength)
Decimal.TryParse(txtWidth.Text, decWidth)
Decimal.TryParse(txtPrice.Text, decPrice)
Decimal.TryParse(txtSquareft.Text, decSquareft)
txtTotalprice.Text = decTotalprice.ToString("C2")
txtSquareft.Text = decSquareft.ToString("N2") & " Sq. ft."
' Calculate the square feet and total price
txtSquareft.Text = txtLength.Text * txtWidth.Text
txtTotalprice.Text = txtPrice.Text * txtSquareft.Text
End Sub
Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
' Clears all the text fields with button click
txtLength.Clear()
txtWidth.Clear()
txtPrice.Clear()
txtSquareft.Clear()
txtTotalprice.Clear()
End Sub
Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
' Exits the form
Me.Close()
End Sub
End Class
There are two primary issues here and I feel like I bring them up at least ten times a day. Firstly, you are trying to write code without knowing what that code has to do. You've considered the end result but not the steps to get there. If you had done that then it would be obvious that your code doesn't what it's supposed to. Secondly, you clearly haven't debugged your code, which is the first thing anyone should do when they don't get the expected result. That would also let you see that your code doesn't make sense IF you considered what each line is supposed to be doing as it does it.
If this was a manual task, you would get the input from the user, perform the calculation, then display the result. Is that what you're doing here? No, it is not. First you get the user input. That's a start, but you're doing it wrong. As it stands, you would end with zero for any invalid input but you're just ignoring that. The next thing you do is display the formatted output that you haven't even calculated yet. If you had debugged, you'd have seen that both decTotalprice and decSquareft are zero at that point. You finally do the calculations, but with the raw text input instead of the numbers you already parsed, and then you display the results unformatted. You've even got a comment in your code that says that you're doing the calculation AFTER you've displayed the formatted output.
Stop writing code and think about what the required steps are to get to your desired result. Parse the user input, perform the calculations with the numeric data and not the unparsed text, then display those results with formatting. Once you have a clear idea of what you have to do AND tested that manually, then you can write code to implement that algorithm, rather than some vague idea in your head that involves a final result and little else.
You're certainly not the only person who makes these mistakes but they are elementary mistakes. They happen partly because of bad teaching in some cases, but they also happen because everyone wants to jump into the part that is sexy and fun, i.e. writing the code, but they don't want to do the harder but just as important part of considering what the code actually has to do. When they don't get the expected result, they throw their hands up without ever really having tried to fix it. If you haven't tried to understand what the code has to do, you can't have tried to make it do that.
I'm having a very strange problem in a VB application. I have a function written like this:
In the innermost condition, two statements are commented out here. These were found to have no effect on the strange behaviour. This is the minimal example I've found causing trouble.
(Note that the names of objects have been changed in this example.)
Private Sub MyForm_CellValidating(ByVal sender As Object, ByVal e As DataGridViewCellValidatingEventArgs) Handles myDGV.CellValidating
Dim dgv As DataGridView = CType(sender, DataGridView)
Select Case dgv.Columns(e.ColumnIndex).Name
Case "uniqueColumn"
' Validate that the values in our unique column are unique.
For i As Integer = 0 To dgv.RowCount - 1
If i <> e.RowIndex Then
' Here i != j, so compare to the value...
If e.FormattedValue = dgv.Rows(i).Cells(e.ColumnIndex).FormattedValue Then
e.Cancel = True
'dgv.ShowRowErrors = True
'dgv.Rows(e.RowIndex).ErrorText = "Data in the unique column must be unique"
End If
End If
Next 'i
Case Else
' Perform no validation.
End Select
End Sub
What trouble, you ask? For some inexplicable reason, whenever the line
e.Cancel = True
is executed, afterwards, nearly all buttons and form widgets in the entire application, including even the close button in its window bar (what a user would use to exit the application) stop doing whatever they previously did and now call this event handler instead.
In other words, commenting out that line (and doing the validation manually when the form is submitted) fixes the problems. I'd like to know why this happens, though. Some pointers:
Here's a list of which things are not affected:
The minimize and maximize button in the top bar.
All objects in its menu bar.
This handler is private to its form class, it's not referenced anywhere else in the application.
I'm at a loss. Just how? What could possibly cause this?
e.Cancel is for stopping the validation when the input is deemed incorrect. This causes the cell to still have focus as the user is expected to correct whatever they did wrong. The CellValidating event will then be raised again whenever the cell is about to lose focus until your code deems the input to be correct.
You can use the Control.CausesValidation property to control whether a control (for instance a button) should raise validation events when it gains focus.
So basically, I believe I am using the correct code yet the database will still not update. It will work for the current session, however, when I stop and restart the program, it appears that the data has not been updated in the database.
The really interesting part is that I am using the same method to update the database elsewhere, which when used and session restarted, the database has been updated.
p.s. I also have the same adapters and binding sources set up etc on both forms
I am so confused, help pls
Code that I believe is correct but is not working: (updating on another form so I have one place where all forms update hence FRMMain. etc)
Private Sub btnConfirm_Click(sender As Object, e As EventArgs) Handles btnConfirm.Click
Dim CurrentPoints As Integer
Dim UpdatedPoints As Integer
CurrentPoints = FRMMain.MyDBDataSet.Tables("TBLPupil").Rows(looopcount)(15)
UpdatedPoints = CurrentPoints + stfPoints
FRMMain.MyDBDataSet.Tables("TBLPupil").Rows(looopcount)(15) = UpdatedPoints
FRMMain.TBLPupilTableAdapter.Update(MyDBDataSet.TBLPupil)
FRMMain.TBLPupilTableAdapter.Fill(MyDBDataSet.TBLPupil)
End Sub
Code that I am using in another form that that DOES work:
Private Sub BtnYes_Click(sender As Object, e As EventArgs) Handles BtnYes.Click
Dim Points As Integer = FRMPupil.Pointss
Dim Cost As Integer = FRMPupil.RewardCost
Points = Points - Cost
FRMPupil.LePoints = Points
MyDBDataSet.Tables("TBLPupil").Rows(FRMLogin.DBLocation)(15) = Points
FRMMain.TBLPupilTableAdapter.Update(MyDBDataSet.TBLPupil)
FRMMain.TBLPupilTableAdapter.Fill(MyDBDataSet.TBLPupil)
Me.Hide()
End Sub
My code is correct but is not working.
No, if it is not working, then it is not correct!
There are different things you can do: DRY, Dont Repeat Yourself. You are repeating the code for updating points at several places in your code. This is error prone. Write it once and re-use it, e.g. by applying the the Repository Pattern. It makes it easier to detect errors and correct them. It allows you to re-use code that has already been tested in other scenarios (on another form).
Debug, debug, debug. Place breakpoints in the not working methods and see what happens. Do all the variables have the expected values? E.g., does looopcount have the same value as FRMLogin.DBLocation? There must be a difference somewhere. See: Navigating through Code with the Debugger or the more recent article Debug your Hello World application with Visual Studio 2017.
I am coding a terminal in VB.net, And when I type in 'help' and press enter, Nothing happens. It is supposed to show 'This is the only command. :P'.
I appear to not be more specific so let me explain what happened.
I put in the code below, I executed the application and then I typed in 'help' and then I hit the enter key then nothing happened at ALL.
Here is the entire code:
Private Sub RichTextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles RichTextBox1.KeyPress
Dim lines = RichTextBox1.Lines
Dim num = lines
Dim textlength = RichTextBox1.TextLength
If Asc(e.KeyChar) = 13 Then
If num.Last.ToString() = "help" Then
RichTextBox1.AppendText("This is the only command. :P\r\n")
End If
End If
End Sub
Please help!
So, having attached a debugger to your code, it was instantly obvious what the problem is... When you get to the comparison, lines.Last() is an empty string.
There are a number of ways to get the 2nd to last line. I prefer LINQ, so here's your code tidied up, using a case and culture-insensitive string comparison (so you can type Help too)...
Private Sub RichTextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles RichTextBox1.KeyPress
If Asc(e.KeyChar) = 13 Then
If String.Equals(RichTextBox1.Lines.Reverse.Skip(1).First(),
"help",
StringComparison.InvariantCultureIgnoreCase) Then
RichTextBox1.AppendText(String.Format("This is the only command. :P{0}", Environment.NewLine))
End If
End If
End Sub
I've also used Environment.NewLine to make your code more portable, and String.Format() to combine the strings in a way that doesn't eat memory for no reason. It's overkill for this example but it shows how it should be done.
It's worth noting that using a debugger is a crucial skill for any developer (well, ok, there is an alternative which is extensive logging, but you need to know both). You will need this skill to solve any number of problems.
In case you're not familiar with the concept, debugging is like pausing your program and letting you examine what's going on, then run a single command at a time to see what the program is doing.
This isn't really an answer, but I noticed that you are writing your code to create a new line incorrectly
You did this:
RichTextBox1.AppendText("This is the only command. :P\r\n")
While it should be something like this:
RichTextBox1.AppendText("This is the only command. :P" & vbCrLf)
By trying your code and removing the
If num.Last.ToString() = "help" Then
End If
And putting this line of code
If Asc(e.KeyChar) = 13 Then
RichTextBox1.AppendText(Environment.NewLine & "This text will appear on the next line.")
End If
It works fine.
Hope this helps.
My program is already working fine, I use a TextBox to capture the barcode scanner input. The purpose of my program is for time and attendance monitoring, the problem is I want to prevent users from using the keyboard to type in their ID's as it would render the barcode scanner and their ID's with barcodes useless.
*I already tried removing the keyboard from the computer and it did work, but the keyboard must not be removed as a requirement...
Option 1:
Get a barcode-scanner that is connected to a serial-port (raw serial device read by a COM port). As most barcode-scanners emulate keyboard strokes there is no way to directly distinguish a barcode scanner input from a keyboard input (see next option) without going low-level (see last update).
One connected to a serial port (or emulated one via USB as serial-ports are not so common anymore) gives you full control on where the input comes from.
Option 2:
Count number of chars typed by time. Barcode-scanners inject a sequence (line) pretty fast compared to typing. Measuring the time used in the textbox by counting key-presses (use CR+LF as a measure point as these are sent by the scanner as well) can give you one method to distinguish if a human is typing (unless there is one typing fast as f) or the content was injected. If timed-out just reject/clear the input.
In addition the checksum of the barcode (if you use one that contains that) can be used to do an extra validation in addition to time measurement.
(you can detect pasting by overriding the ctrl + v as in the next option).
Option 3:
Combine option 2 but instead of measure in the textbox tap into the ProcessCmdKey() function (by overriding it) and measure there if textbox has focus. This way you can first buffer input, measure time and if within a set time-out value, inject the line into the textbox.
Update:
Option 4: a non-technical approach -
Usability improvements: make it visually very clear that bar-codes must be entered with a scanner and not typed. I am including as an option as it is simple and if made correct also effective (there's no right answer of what is correct unfortunately).
Approached could include f.ex. a watermark in the textbox ("Don't type, scan!" or something in that order). Give it a different color, border, size etc. to distinguish it from normal textboxes, and have a help text associated and available at all time that improves clarity.
I had the same issue and I did the following:
I set an int variable digitsPrevTyped = 0
In the "TextChanged" event of my textbox I added this (the textbox has a maxsize of 17 chars):
Private Sub tbxScannedText_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles tbxScannedText.TextChanged
If tbxScannedText.Text.Length >= 17 Then
SearchFunction(False)
Else
digitsPrevTyped = tbxScannedText.Text.Length
End If
End Sub
Then in my "SearchFunction" I check the following:
Dim inputMethod As Char
If tbxScannedText.TextLength = 17 And digitsPrevTyped = 0 Then
inputMethod = TEXT_SCANNED
Else
inputMethod = TEXT_MANUALLY_ENTERED
End If
If the textbox initially had a length of 0 chars and now has a length of 17 chars it means that the text was scanned. If the length of the previously typed text is less than 17 chars, then the text was typed.
It is very basic but it works for me.
The other possible workaround is to handle keypress event to restrict user input. Do not allow direct input from keyboard and leave the readonly false.
Set following in KeyPress event handler
Private Sub Textbox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles Textbox1.KeyPress
e.Handled = True
End Sub
Just disable the keyboard anyway.. when using barcode you can disable the keyboard without using readonly on the textbox..
on keypress event put some code i.e
if e.keychar <> chrw(0) then
e.keychar = chrw(0)
end if
that condition will automatically be trigged when user type anything.. you will forcibly disable any input from user but not from barcode
why not use an "alias" in the bar code like "123##$!" (but make it stupid long) is "JSMITH" and set the font color to the same as the background color in the textbox. The user can't see what they're typing or what the bar code value is when it's scanned.
Super simplistic approach that doesn't really require anything added aside from another field in the the user table.
This is an old post, but it took me some time to figure out a relatively clean way to use a barcode scanner and combobox so this is for future users.
Barcode scanners can often be configured to append carriage return and line feed to the end of the scan. I have a form that can take user input or barcode scanner input into a bound combobox using the _PreviewKeyDown property and trapping on the value "Keys.Enter".
Example:
If ((e.KeyCode = Keys.Enter) Then
'do stuff
Else
'do other stuff
End if
Verifying the data exists in the datasource is a bit trickier because the SelectedValue property of the combobox doesn't update so that event doesn't fire. I used a custom method to verify that the value scanned exists in the datasource. This method uses the .Text property of the combo box. It uses:
Me.combobox.findexactstring(Me.combobox.Text)
If e.KeyCode = Keys.Enter And txt.Text.Length > 0 Then
'To Do
Else
'To Do
End if
All of my scanner input goes into a "hidden" textbox, which then fills the visible ones as needed depending on the input. This, of course, means you need to keep track of where the focus is. Any type of control that can get focus will then make a call in those events to return focus to whatever the "active" textbox is at that time, which is normally the hidden one. For example...
Private Sub buttons_gotFocus(sender As System.Object, e As System.EventArgs) Handles btnPrint.GotFocus, btnInMVPageDown.GotFocus, btnAdv.GotFocus, btnManual.GotFocus, btnResend.GotFocus, dgvInbound.GotFocus, dgvOutbound.GotFocus, TCRole.GotFocus
Try
activeTextbox.Focus()
Catch ex As Exception
'ignore any errors
End Try
End Sub
Most other textboxes are disabled by default, and only enabled under certain conditions. Once that entry is done they are disabled and the hidden one will get focus again. Works like a charm.
There's no need to record previous typed characters.
Here's my solution:
Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged
If TextBox1.Text.Length >= 17 Then '17 or the number of characters your scanner gets.
MsgBox("scanned")
TextBox1.Clear()
Else
If TextBox1.Text.Length <> 0 Then TextBox1.Clear()
End If
End Sub
This answer will handle any fast typing.
Dim scanner_input As Boolean = False
Dim start_typing As DateTime
Private Sub TextBox_part_number_TextChanged(sender As Object, e As EventArgs) Handles
TextBox_part_number.TextChanged
If (TextBox_part_number.Text.Length = 1) Then
start_typing = DateTime.Now
scanner_input = False
'' MsgBox(start_typing.ToString)
ElseIf (TextBox_part_number.Text.Length > 7) Then
If (calc_typing_time(start_typing) < 500) Then
scanner_input = True
Else
scanner_input = False
End If
End If
End Sub
Function calc_typing_time(time_started As DateTime)
Dim time_finished As DateTime
time_finished = DateTime.Now
Dim duration As TimeSpan = time_finished - time_started
Dim time_diff As String = duration.TotalMilliseconds
Return time_diff
End Function
Most of the scanners has a driver to communicate with (Opos) it has functions to open the scanner port and listen to the scanning , so you take the result and decode it in the background and then display the result in the Textbox... what you need to do it to check your barcode scanner's brand go to it's website and download the driver and its manual.
You should just mark your textbox as readonly.