Deleting Lines from Array - arrays

I have an array of lines and I want at some point to erase some of them.
Here's a sample of the code:
Dim canvas As New Microsoft.VisualBasic.PowerPacks.ShapeContainer
Dim lines(20) As PowerPacks.LineShape
Dim it As Integer = 0
Private Sub GoldenSpi_Load(sender As Object, e As EventArgs) Handles MyBase.Load
canvas.Parent = Me
lines.Initialize()
iter.Text = 0
End Sub
Private Sub iter_TextChanged(sender As Object, e As EventArgs) Handles iter.TextChanged
If (it > iter.Text And iter.Text <> 0) Then
ReDim Preserve lines(iter.Text - 1)
End If
If (it <> iter.Text) Then
it = iter.Text
End If
For i As Integer = 1 To iter.Text
lines(i - 1) = New PowerPacks.LineShape(canvas)
lines(i - 1).StartPoint = pA(i)
lines(i - 1).EndPoint = pB(i)
lines(i - 1).BringToFront()
Next
End Sub
After I execute the program, the lines are created. But when I give a value to my textbox that is smaller than the variable 'it', it justs delete the last line and not the rest. Also I saw while debugging that the size of array is reduced. So that means that the contents beyond the size are still kept? Why is that?. Any help is appreciated. Thanks.
EDIT: I tried to create the List like this:
Dim lines As New Generic.List(Of PowerPacks.LineShape)
Private Sub iter_ValueChanged(blabla) Handles iter.ValueChanged
If (it > iter.Value And iter.Value <> 0) Then
lines.RemoveRange(iter.Value - 1, lines.Count - iter.Value)
End If
For i As Integer = 1 To iter.Value
InitPoints()
If i - 1 = lines.Count Then
Dim line As New PowerPacks.LineShape
With line
.StartPoint = pA(i)
.EndPoint = pB(i)
.BringToFront()
.Parent = canvas
End With
lines.Add(line)
End If
Next
End Sub
But still the lines are visible in the form. I debugged it and saw that the list size decreased. The same problem when I had an array. What is going?...

I recommend changing iter.Text to cint(iter.Text), as there is a chance it's comparing both values as text (which is compared differently).
I'd also recommend changing Dim lines(20) As PowerPacks.LineShape to Dim lines As new generic.list(of PowerPacks.LineShape)
That way you don't have to worry about ReDim Preserve (which can be slow when you do it in a loop), and you can easily insert items into any index if you whish

You should use Option Strict On in your project, in order to avoid implicit conversion between types which can give you errors or, worse, unexpected behaviors.
On the other hand, you should not have a TextBox to store numbers unless there is a need. Use a NumericUpDown, for example. Take a look at the MSDN Documentation.
And now, for the array, I recommend using a List, which has all the methods implemented that you need to handle the elements, and has a .ToArray() method that will give you the array if needed.
Try something like this:
Dim it As Integer = 0
Dim lines As New List(Of PowerPacks.LineShape)()
Sub iter_TextChanged(sender As Object, e As EventArgs) Handles iter.TextChanged
Dim iTxt As Integer
Try
iTxt = Integer.Parse(iter.Text)
If it > iTxt AndAlso iTxt <> 0 Then
End If
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Sub
I was going to write to you an example, but I realized that I don't know exactly what you're trying to do. Could you explain?

Related

Populating two one-dimensional arrays with text file

For my Visual Basic final, my program is required to read data from a text file into two different arrays, each being one-dimensional. The following is my code for doing so:
Option Explicit On
Option Infer Off
Option Strict On
Public Class frmMain
'Constant for filename and a dirty flag variable
Const INVENTORY_FILENAME As String = "inventory.txt"
Dim noFile As Boolean = False
Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'Populates DVD listbox with text file data upon load
'Variable for reading the file
Dim myFile As IO.StreamReader
'Declaring arrays for DVD names and prices
Dim arrayDVD() As String
Dim arrayPrice() As Double
'Variables for populating arrays with respective data
Dim dvdName As String
Dim dvdPrice As Double
Dim i As Integer = 0
'Checking that file exists then reading data to each array
If IO.File.Exists(INVENTORY_FILENAME) Then
myFile = IO.File.OpenText(INVENTORY_FILENAME)
'Read data to arrays
Do Until myFile.Peek = -1
dvdName = myFile.ReadLine()
dvdPrice = Double.Parse(myFile.ReadLine())
arrayDVD = dvdName
arrayPrice = dvdPrice
'Using arrays to populate multicolumn listbox
lstDVD.Items.Add(arrayDVD(i) & arrayPrice(i))
i += 1
Loop
'Closing the file
myFile.Close()
End If
End Sub
End Class
The text file alternates names and prices of DVDs to be read as individual lines, making the arrays parallel:
Pulp Fiction
9.99
Jumanji
13.99
And so on...
I'm receiving a value type error code stating that I cannot convert 'String' to 'String()' or convert 'Double' to 'Double()' when setting the arrays' values equal to their respective variables. Is there a way to correct this? Thanks in advance!
These lines are wrong:
arrayDVD = dvdName
arrayPrice = dvdPrice
arrayDVD and arrayPrice are arrays. You need to assign to a specific element in each of those arrays:
arrayDVD(i) = dvdName
arrayPrice(i) = dvdPrice
Don't forget to make sure the arrays actually have enough elements for this.
Hint: ReDim Preserve is pretty much the least efficient way possible to make sure an array is big enough. Each use will allocate a brand new array, copy the elements one at a time, assign the new array to the old reference, and then release the old array. It does not preserve in-place. Nevertheless, if this is a 100-level course it might be what you are expected to do at this point.
Finally, you should never use Double when working with money (use Decimal instead).
Separate from the question, here is how I might approach this without the weird array limitation:
Private Iterator Function ReadInventoryFile(filePath As String) As IEnumerable(Of (String, Decimal))
Using rdr As New StreamReader(filePath)
Dim DVDName As String = Nothing
While (DVDName = rdr.ReadLine()) IsNot Nothing
Yield (DVDName, Decimal.Parse(rdr.ReadLine()))
End While
End Using
End Function
Const INVENTORY_FILENAME As String = "inventory.txt"
Private data As List(Of (String, Decimal))
Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Try 'Replaces the File.Exists() check
data = ReadInventoryFile(INVENTORY_FILENAME).ToList()
For Each item As (String, Decimal) In data
lstDVD.Items.Add($"{item.Item1}{vbTab}{item.Item2:C}")
Next
Catch
' Actually do something here. Empty catch blocks are rarely correct.
' Note I catch at this level, rather than in the ReadFile() method.
End Try
End Sub

Visual Basic code works but is inelegant - any suggestions?

I am trying to stay ahead of my Year 12 Software class. Starting to work with records and arrays. I have answered the question, but the solution feels very clunky. I am hoping someone has suggestions/links for completing this task in a more efficient way.
The task: read in lines from a text file and into a structure, and then loop through that, populating four list boxes if an animal hasn't been vaccinated.
Here's the code:
Imports System.IO
Public Class Form1
'Set up the variables - customer record, total pets not vaccinated, total records in the file, and a streamreader for the file.
Structure PetsRecord
Dim custName As String
Dim address As String
Dim petType As String
Dim vacced As String
End Structure
Dim totNotVac As Integer
Dim totalRecCount As Integer
Dim PetFile As IO.StreamReader
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Private Sub btnLoad_Click(sender As Object, e As EventArgs) Handles btnLoad.Click
'set an array of records to store each record as it comes in. Limitation: you need to know how many records in the file. Set the array at 15 to allow for adding more in later.
Dim PetArray(15) As PetsRecord
'variables that let me read in a line and split it into sections.
Dim lineoftext As String
Dim i As Integer
Dim arytextfile() As String
'tell them what text file to read
PetFile = New IO.StreamReader("patients.txt")
totNotVac = 0
Try
totalRecCount = 0
' read each line in and split the lines into fields for the records. Then assign the fields from the array. Finally, reset the array and loop.
Do Until PetFile.Peek = -1
'read in a line of text
lineoftext = PetFile.ReadLine()
'split that line into bits separated by commas. these will go into the array.
arytextfile = lineoftext.Split(",")
'dunno whether this is the best way to do it, but stick the array bits into the record, and then clear the array to start again.
PetArray(totalRecCount).custName = arytextfile(0)
PetArray(totalRecCount).address = arytextfile(1)
PetArray(totalRecCount).petType = arytextfile(2)
PetArray(totalRecCount).vacced = arytextfile(3)
totalRecCount += 1
Array.Clear(arytextfile, 0, arytextfile.Length)
Loop
For i = 0 To PetArray.GetUpperBound(0)
If PetArray(i).vacced = "No" Then
lstVaccinated.Items.Add(PetArray(i).vacced)
lstCustomer.Items.Add(PetArray(i).custName)
lstAddress.Items.Add(PetArray(i).address)
lstPetType.Items.Add(PetArray(i).petType)
totNotVac += 1
lblVacTotal.Text = "The total number of unvaccinated animals is " & CStr(totNotVac)
End If
Next
Catch ex As Exception
MsgBox("Something went wrong with the file")
End Try
PetFile.Close()
End Sub
Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
Close()
End Sub
End Class
And one line from the patient.txt file:
Richard Gere,16 Sunset Blvd,Gerbil,No
I hope this isn't out of place.
Regards,
Damian
If you want to use Streams be aware that they need to be disposed.
File.ReadAllLines returns an array of lines. Since the array is initialized where it is declared we don't need to specify a size.
If you use List(Of T) you do not have to know in advance the number of elements in the list. Avoids the limitation of array.
Using a For Each avoids having to use the size. The small c following "," tells the compiler that this is a Char which is what .Split is expecting. If you had Option Strict On, which you always should, you would have seen an error. You add items to the list by creating a New PetsRecord. The parametrized Sub New receives the values and sets the properties.
Don't change the display in the label on each iteration. Use an interpolated string (preceded by a $) which allows embedded variables surrounded by braces { }. It is not necessary to change the number to a string as it is implied by the interpolator. (Available in VS2015 and later)
Public Structure PetsRecord
Public Property custName As String
Public Property address As String
Public Property petType As String
Public Property vacced As String
Public Sub New(name As String, add As String, pType As String, vac As String)
custName = name
address = add
petType = pType
vacced = vac
End Sub
End Structure
Private Sub btnLoad_Click(sender As Object, e As EventArgs) Handles btnLoad.Click
Dim lines = File.ReadAllLines("patients.txt")
Dim lstPet As New List(Of PetsRecord)
For Each line In lines
Dim splits = line.Split(","c)
lstPet.Add(New PetsRecord(splits(0), splits(1), splits(2), splits(3)))
Next
Dim totNotVac As Integer
For Each pet In lstPet
If pet.vacced = "No" Then
lstVaccinated.Items.Add(pet.vacced)
lstCustomer.Items.Add(pet.custName)
lstAddress.Items.Add(pet.address)
lstPetType.Items.Add(pet.petType)
totNotVac += 1
End If
Next
lblVacTotal.Text = $"The total number of unvaccinated animals is {totNotVac}"
End Sub
If you don't need the 'PetsRecord' array to store data, take a look at the following code:
Dim totNotVac As Integer
Private Sub btnLoad_Click(sender As Object, e As EventArgs) Handles btnLoad.Click
File.ReadAllLines("your text file path").ToList().ForEach(Sub(x)
lstVaccinated.Items.Add(x.Split(","c)(0))
lstCustomer.Items.Add(x.Split(","c)(1))
lstAddress.Items.Add(x.Split(","c)(2))
lstPetType.Items.Add(x.Split(","c)(3))
totNotVac += 1
End Sub)
lblVacTotal.Text = "The total number of unvaccinated animals is " & CStr(totNotVac)
End Sub

Working with Array As New Object does not work

my VBA-code is making trouble. I made a Class module called "clsColl" with the Properties. When i declare a variable as "clsColl" everything working fine, but when i declare an array as "clsColl" i get an error
"Object variable or With block variable not set", if i use this array in another sub, which i called in the first sub.
I made a short example with just the code in it which making trouble.
First my class module "clsColl"
Option Explicit
Public name As String
Public weight as single
Now the code which is working
Sub workingA()
Dim persona As New clsColl
Call workingB(persona)
End Sub
Sub workingB(persona As cls Coll)
persona.name = "phil"
persona.weight = 100
End Sub
Now the code which is not working
Sub failingA()
Dim persona() As New clsColl
ReDim persona(1 to 5)
Call failingB(persona)
End Sub
Sub failingB(persona() As cls Coll)
persona(1).name = "phil"
persona(1).weight = 100
End Sub
I get an error, just by changing my code from using a variable to using an array.
Now i get an error Object variable or With block variable not set" with the second code, but i don't know why. I want to know why using an array as an object is making trouble like this, while using a normal variable is working fine.
Your code line
Dim persona As New clsColl
is a combination of
Dim persona As clsColl
If persona Is Nothing Then Set persona = New clsColl
and it is bad practice using that combining syntax at all, at least in my opionion.
Now for the array this cannot work anymore as each array item must be Set to be an clsColl object first:
Sub notMorefailingA()
Dim persona() As clsColl
Dim i As Integer
ReDim persona(1 To 5)
For i = 1 To 5
Set persona(i) = New clsColl
Next
Call notMorefailingB(persona)
End Sub
Sub notMorefailingB(persona() As clsColl)
persona(1).name = "phil"
persona(1).weight = 100
End Sub
You have nothing in the array you need to populate the array with classes. Your Dim wont use the new keyword, you'll create new classes and add them into the array.
Sub test1()
Dim d As New clsDimension
Dim arrDimensions(5) As clsDimension
Set arrDimensions(0) = d
arrDimensions(0).Breadth = 100
arrDimensions(0).Depth = 200
End Sub
or in a similar approach to your post
A class for the array, like so, clsDimensionArray
Private arrDimensions() As clsDimension
Public Property Get ArrItems(x As Long) As clsDimension
Set ArrItems = arrDimensions(x)
End Property
Public Sub Create(lngSize As Long)
Dim l As Long
Dim d As clsDimension
ReDim arrDimensions(lngSize - 1)
For l = 0 To UBound(arrDimensions)
Set d = New clsDimension
Set arrDimensions(l) = d
Set d = Nothing
Next l
End Sub
and using like so
Sub test1()
Dim arrDimensions As New clsDimensionArray
arrDimensions.Create (100)
arrDimensions.ArrItems(90).Depth = 50
arrDimensions.ArrItems(90).Breadth = 100
End Sub
Keeps it nice and tidy :o)

NullReferenceException was unhandled VB.net Structure with Array

Public Class Form1
Structure Crap
Dim CrapA As Integer
Dim CrapB As Single
Dim CrapC() As Long
Private Sub Initialize()
ReDim CrapC(0 To 100)
End Sub
End Structure
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim Stuff(0 To 2) As Crap
Stuff(0).CrapA = 16
Stuff(1).CrapA = 32
Stuff(2).CrapA = 64
'This is the line where the NullReferenceException is thrown
Stuff(0).CrapC.Initialize()
For x = 0 To 100
Stuff(0).CrapC(x) = x ^ 2
Next x
MsgBox(Stuff(0).CrapA)
MsgBox(Stuff(1).CrapA)
MsgBox(Stuff(2).CrapA)
For x = 0 To 100
MsgBox(Stuff(0).CrapC(x))
Next x
End Sub
End Class
So this is a pretty simple program with a baffling error. All I want is an array in my user defined type. I'm moving from VB6 to .net and everything I've read, including What is a NullReferenceException, and how do I fix it? which is a hearty read, doesn't help. Seems I'm stuck in 1999, lol. I understand that the array CrapC is null, it's making it not null that's the problem.
The error happens here:
Stuff(0).CrapC.Initialize()
because the Crap() contains three instances of Crap but you never initialize the CrapC field which is a Long(). So you can call Initialize on Nothing(null). In most cases you don't need this method anyway: "This method is designed to help compilers support value-type arrays; most users do not need this method."
Instead use this array initializer to get a Long() with 100 longs:
Stuff(0).CrapC = New Long(99) {}

Why Won't My Array Sort? (Visual Basic)

I'm working on a project, for school, that reads text from a .txt file to an array. After doing that, I'm supposed to sort the array, alphabetically, and then list the contents in a listbox. Here is my code:
Imports System.IO
Public Class Form1
'Allow array to be accessed by the entire program
Public books(1) As String
Private Sub btnView_Click(sender As Object, e As EventArgs) Handles btnView.Click
'Declare variables
Dim sr As New StreamReader("C:\Users\Bryson\Desktop\BooksinStock.txt")
Dim book As String
Dim i As Integer = 0
'Establish loop to read contents of the text file into the array and list the array in the listbox
'the sr.Peek = -1 simply means that the reader has reached the end of the file and there is nothing more to be read
Do Until sr.Peek = -1
book = sr.ReadLine()
'ReDim allows the array to grow with the set amount of books in text file
ReDim books(books.Length + 1)
books(i) = book
i += 1
Loop
Array.Sort(books)
lstBoxInventory.Items.Add(books(i))
End Sub
End Class
However, when I run the program, I receive an error on the lstBoxInventory.Items.Add(books(i)) line that says "an unhandled exception of the type 'System.ArgumentNullException' occurred in System.Windows.Forms.Dll
I've tried to lay the code out in various ways to get the sort to work but keep coming up short. Does anyone know how to get rid of this null error?
The problem happening because "i" is larger than the highest index
Do Until sr.Peek = -1
book = sr.ReadLine()
ReDim books(books.Length + 1)
books(i) = book
i += 1 'This is adding 1 to the very end
Loop
Array.Sort(books)
lstBoxInventory.Items.Add(books(i)) 'When the items are being added it is trying to add an extra i that does not exist
edit
Honestly I would change the format to use ReadAllLines and list(of String)
Something like (Im writing code from memory)
Dim bookList as new List(of String)
Dim bookTextFile as String() = File.ReadAllLines("C:\booklist.txt")
for each book as String in bookTextFile
bookList.add(book)
next
bookList.Sort
Edit Again
Just using this
Dim bookList As String() = System.IO.File.ReadAllLines("C:\Users\Bryson\Desktop\BooksinStock.txt")
creates a single dimension array ..
Strings() are single Arrays String(,) are two dimensional Arrays
Honestly your whole homework could be
Dim bookList As String() = System.IO.File.ReadAllLines("C:\Users\Bryson\Desktop\BooksinStock.txt")
Array.Sort(BookList)
boom - done.
Test it using
for each book as String in BookList
Msgbox(book)
next
You could do
Dim bookList As String() = System.IO.File.ReadAllLines("C:\Users\Bryson\Desktop\BooksinStock.txt")
Dim books(bookList.Length - 1) As String 'This is the same as ReDim
For x As Integer = 0 To bookList.Length - 1
books(x) = bookList(x)
Next
Array.Sort(books)
but you would literally be saying bookList = books
But.... if you just want to get your code working, just try this
lstBoxInventory.Items.Add(books(i -1)) 'This takes away the extra i that you added

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