Dimension Of Variable Inside For Loop
Mar 30, 2010
Using VB.NET .NetFramwork 3.5. This fails and strikes me as odd. Is this correct behavior:
Public Sub TestForEach()
For index As Integer = 1 To 10
Dim z As Integer
Assert.AreEqual(0, z)
z = index
Next
End Sub
I would expect z to always equal 0 as I thought the dim-ing of an integer would set the value to 0. If you run this. It fails at the second loop. For some reason z retains it's value of 1. I know I can manually initialize z to = 0, but I wanted to know if this is a bug or expected behavior.
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Aug 26, 2011
For i As Integer = 1 To 10
Dim j As Integer = 10
Next
now my question is, Is memory allocated to j every time its executed inside for loop? or only value of 10 is assigned on subsequent iterations?
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Mar 27, 2012
Today I investigated a logical bug in our software and figured out that this is related to the way VB.NET thread variables inside a loop.Let's say I have the following code:
Dim numbers As New List(Of Integer) From {1, 2, 3, 4, 5}
For Each number As Integer In numbers
Dim isEven As Boolean
[code]....
The problem is that isEven is declared but not assigned.In this specific case, it would be correct to write dim isEven as Boolean = false but I haven't done this.In VB.NET, a variable that is declared inside a for loop keeps its value for the next itaration. This is by design: [URL]but this is also dangerous pitfall for programmers.
However, until now, I haven't been aware of this problem/behaviour. Until now.Most of our code base is C# anyway, which doesn't allow the use of an uninitialized variable, so there is no problem. But we have some legacy code that is written in VB.NET that we have to support. So the best thing would be to generate a warning or even an error in this specific case.But even with Option Explicit / Option Strict this does not generate a warning / an error.Is there a way make this a compile time error or maybe a way to check this with FxCop?
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Nov 3, 2011
I had insert value from datagridview to array
but how to make the array become for loop function?
Dim rowNo As Integer = 0
counter = dgv.RowCount()
[code].....
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Jul 16, 2009
How do you split the 2 dimension into 2 variable from a string?
what i have:
RECT (-9895480 4134720, -3298480 9523800)
what i want to appear in the message box:
-9895480 4134720 - x axis
-3298480 9523800 - y axis
how do i split the string into 2 variables with "," as the splitting refernce point? I'm using vb08.
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May 5, 2010
is it possible to dynamically dimension a variable?in my case, i have a chart that has a varying number of series on it depending on the data extracted and in order to use those series, i have to dimension them manually before adding points to them, IE:
Dim series1 as New Series()
Dim series2 as New Series()
etc
etc
my series data is contained in a datatable, so i'll know the count required, but it will change at runtime, so obviously doing something like this won't work, but explains what i'm trying to do:
dim recordcount as integer = datatable.rows.count
for i = 1 to recordcount
dim "series"+recordcount.tostring as new series()
next
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Feb 4, 2012
i just got 1 question how do u create a (in excel ) variable table (database) inside a function which could be called for filling and reading through "for to next" loop module
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Feb 19, 2010
I am sure this has had to have been answered somewhere but after looking on the web I cant find anything addressing variables in variables. For instance say I have var1, var2, var3, var4 decalred. How can I create a loop assignment? Something like var & i = "variable 1". So instead of "var1" I have the numeric piece be a variable.
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Feb 5, 2009
I have an one dimension string array ar1
ar1(0) ="One;is;a;dog;"
ar2(1)="Two;is;a;cat;"
...
I want to convert ar1 into ar2 which is a two dimension array
ar2(0)(0)="One";ar2(0)(1)="is";ar2(0)(2)="a";ar2(0)(3)="dog"
etc
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Mar 28, 2012
I'm foolin round with stream reader/writer and I'm running into this problem: If I have my if/then statement inside my loop I get a million msgboxes(which I understand why), however if I put it outside my loop, and the if/then returns a false then the whole program freezes up. I can't move my mouse around, I can't click on any objects, ect. Here is what I'm using:
[Code]...
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Sep 7, 2011
here is some simple code:
0: dim varA = 0
thread.sleep(1000)
GoTo 0
I was wondering how do I name each new variable a different name each time through the loop (i.e. varA1, varA2, varA3)
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Feb 26, 2009
Im having a problem with a loop inside a C++ dll being called from VB. I want this loop to update a global variable, but when I call the function the variable does not update the first time round, but does so every subsequent time.
This is how I am trying to update the variable.
else
{
::nScore = nHighest;
[Code].....
As a workaroud I am forcing the variable to be what I want in the VB code
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Jul 28, 2009
i trying to insert into database everytime a loop complete. but there is a syntax error saying "Incorrect syntax near '1'" at myCommand.ExecuteNonQuery(). here is my code and i really don't where went wrong. expert,
[Code]...
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May 27, 2009
How do I get the position of the XML element in this loop?
For Each objNode In objDoc.SelectNodes("//books/book")Next
What I want in output would be something like
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May 19, 2009
Is it possible to change many labels inside a for loop? Let's say I have labels 1 to 4. Can I do something like:
for i = 1 to 4
label%i.text = some text
next
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Feb 25, 2011
I am having trouble using FOR loop with array in query.What I am trying to do is for all the data pulled out of database I convert it to an array list and then string (this works fine). After that I am trying to make a FOR loop query for each of the data pulled out and this is where i am having trouble.
[Code]...
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Mar 23, 2012
I am writing a program and i need to declare matrices but there will be a different number to declare everytime the program is run so I was wondering if anyone knew how to declare them inside a for loop
eg.
For i = 1 to NumberOfMatrices
Dim matrix i (5,5) As Double
Next
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May 18, 2010
I would like to be able to stop a loop while executing using the ESC key.I've found a lot about using the above key from within a Form (for example, to unload it), but very little for the use of the key within a Procedure (Sub, Function) and particularly with respect of preventing a loop from carrying on execution.
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Jun 27, 2012
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim s As New Staff
[Code]....
Basically I am trying to update each record with 2 random numbers each time the button was clicked,my problem now is, the system will update the record but the data was wrong. Example, by right all data should be different (randomly string) but for some row it was updated with same data but in randomly, something row1 row2 row3 has exactly same data for column 1 and 2 then row 3 has distinct data, second time, row1 row2 same data row3 ro4 with different data. It is in random sequence. When I add a MsgBox to do testing in the For loop the data was updated correctly with all different data.
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Apr 23, 2012
For my own basic understanding ... what is the difference between these two snippets?
Dim y As Integer
For x As Integer = 1 To 100
y = x
[code].....
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Oct 15, 2011
I have some variables that are distinct by numbers, like in1, in2...If I have for loop, how would I access those variables, using the counter, and attaching it to the variable?I believe in JAVA, you could just use in+ct... where ct is the counter to access the variable.also how could you make a new variable in the for loop?Initially I had variables declare outside of the for loop. The problem was how to access those variables using the for loop.
var_nm1 = in1.Text
var_nm2 = in2.Text
var_nm3 = in3.Text
Dim nmList(2) As Integer
[code]....
This is object oriented programming, and I made the textboxes in1, in2, and in3 using the GUI editor. that was so easy.
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Feb 11, 2010
I would like to show that the computer is busy and not frozen during a long file transmitted over Serial Port.I have the following loop.The intention was to show one "*" for every line sent.
While (fs.EndOfStream = False)
lineRead = (fs.ReadLine)
TextBox1.Text = "* "
SerialPort1.Write(lineRead)
End While
I can see the data sent on the Scope but the chain of "******...." show up after the transmission ends.The WHILE LOOP is actually working but the TextBox1.Text = "*" is not writing to screen.I would like to see the train of ******** same time as the transmission is active.The * is to show that the computer is busy and not frozen.Writing a copy of the actual serial data transmitted to screen is also another option that I can use.
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Jun 12, 2010
how to wait for a second inside a loop?
This is what I tried (including everything else in my form):
Public Class test5
Public z As Integer
Private Sub test5_GotFocus1(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.GotFocus
[Code]....
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Jan 12, 2011
I have several textboxes in a winform, some of them are inside a groupbox. I tried to loop over all textboxes in my form:
For Each c As Control In Me.Controls
If c.GetType Is GetType(TextBox) Then
' Do something
[code].....
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Nov 11, 2010
I have an FTP connection with around 50 folders in it, I have one file that I need to upload to all of these folders, how can I get the list of these folders in there so I can go ahead and upload the file automatically? The folder # keeps increasing and I can't manually keep uploading the file to each folder.
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Jul 8, 2010
Im using Vb.net visual studio 2008. i have got a process(system.diagnostics.process) to be run in background and it updates the Ui thread progressbar and a label and i have worked it using backgroundworker.runworkerAsync. Now the problem is i have to work the same process for a number of time with different inputs.
The code block is :
Private Sub fnStartEvent(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.click
Dim inputFolder = Directory.GetFiles(textboxSourceFolder.text)
Dim currentNumberOfFile As Integer=1
[code]....
The problem in here is the fnStartEvent method once gets started, it calls BackgroundWorker1.runWorkerAsync process and that runs in a seperate thread and does not wait for the thread to complete and it moves to the next line of code i.e loops to the next item and it returns to same BackgroundWorker1.runWorkerAsync line and throws exception that it is already running.
Tried
1.
Private Sub fnStartEvent(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.click
Dim inputFolder = Directory.GetFiles(textboxSourceFolder.text)
Dim currentNumberOfFile As Integer=1
[code]....
But this does not updates the Ui thread used to denote progress.
2.Put the whole process inside the DoWork thread and loop for each file in there itself, but that to returns the cross thread error in progress bar updation.what is the standard procedure in executing a loop for the backgroundworker to wait for finishing as well as update the UI without blocking it.
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Jun 11, 2011
How do I save the information from each activation of the code inside the loop. I decided to try this a different way. I also need to know how to create colums in a label?
For countInteger As Integer = 0 To 3
seatsSoldInteger = ticketDetail(countInteger).seatsSoldInteger
costDecimal = ticketDetail(countInteger).costDecimal
totalTicketSalesDecimal = ticketDetail(countInteger).totalCostDecimal
[code].....
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Nov 14, 2010
Dim tbox As Control
Dim oWrite As System.IO.StreamWriter
oWrite = IO.File.CreateText("c:Template.BBT")
[code]......
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Jun 1, 2011
if I have the following vb code,
for i = 0 to dTable.Rows(i).Count -1
Dim sql As String = ""
Dim strConn As String = ConnString
[Code]....
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Apr 22, 2011
I need to loop inside listview and its columns Sub Items. I'm currently using this.
For Each item As ListViewItem In ListView1.Items
For Each si As ListViewItem.ListViewSubItem In item.SubItems
Next
Next
But it over loops on the items causing the code to produce incorrect tasks.
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