Splitting string every 100 characters not working - vb.net

Question

I am having a problem where I just can't seem to get it to split or even display the message. The message variable is predefined in another part of my code and I have debugged to make sure that the value comes through. I am trying to get it so that every 100 characters it goes onto a new line and with every message it also goes onto a new line.
y = y - 13
messagearray.AddRange(Message.Split(ChrW(100)))
Dim k = messagearray.Count - 1
Dim messagefin As String
messagefin = ""
While k > -1
messagefin = messagefin + vbCrLf + messagearray(k)
k = k - 1
End While
k = 0
Label1.Text = Label1.Text & vbCrLf & messagefin
Label1.Location = New Point(5, 398 + y)

Answer 1

You can use regular expression. It will create the array of strings where every string contains 100 characters. If the amount of remained characters is less than 100, it will match all of them.
Dim input = New String("A", 310)
Dim mc = Regex.Matches(input, ".{1,100}")
For Each m As Match In mc
'// Do something
MsgBox(m.Value)
Next

Answer 2

You can use LINQ to do that.
When you do a Select you can get the index of the item by including a second parameter. Then group the characters by that index divided by the line length so, the first character has index 0, and 0 \ 100 = 0, all the way up to the hundredth char which has index 99: 99 \ 100 = 0. The next hundred chars have 100 \ 100 = 1 to 199 \ 100 = 1, and so on (\ is the integer division operator in VB.NET).
Dim message = New String("A"c, 100)
message &= New String("B"c, 100)
message &= New String("C"c, 99)
Dim lineLength = 100
Dim q = message.Select(Function(c, i) New With {.Char = c, .Idx = i}).
GroupBy(Function(a) a.Idx \ lineLength).
Select(Function(b) String.Join("", b.Select(Function(d) d.Char)))
TextBox1.AppendText(vbCrLf & String.Join(vbCrLf, q))
It is easy to see how to change the line length because it is in a variable with a meaningful name, for example I set it to 50 to get the output
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC

Answer 3

You can use String.SubString to do that. Like this
Dim Message As String = "your message here"
Dim MessageList As New List (Of String)
For i As Integer = 0 To Message.Length Step 100
If (Message.Length < i + 100) Then
MessageList.Add(Message.SubString (i, Message.Length - i)
Exit For
Else
MessageList.Add(Message.SubString (i, 100))
End If
Next
Dim k = MessageList.Count - 1
...

Answer 4

Here is what your code produced with a bit of clean up. I ignored the new position of the label.
Private Sub OpCode()
Dim messagearray As New List(Of String) 'I guessed that messagearray was a List(Of T)
messagearray.AddRange(Message.Split(ChrW(100))) 'ChrW(100) is lowercase d
Dim k = messagearray.Count - 1
Dim messagefin As String
messagefin = ""
While k > -1
messagefin = messagefin + vbCrLf + messagearray(k)
k = k - 1
End While
k = 0 'Why reset k? It falls out of scope at End Sub
Label1.Text = Label1.Text & vbCrLf & messagefin
End Sub
I am not sure why you think that splitting a string by lowercase d would have anything to do with getting 100 characters. As you can see the code reversed the order of the list items. It also added a blank line between the existing text in the label (In this case Label1) and the new text.
To accomplish your goal, I first created a List(Of String) to store the chunks. The For loop starts at the beginning of the input string and keeps going to the end increasing by 10 on each iteration.
To avoid an index out of range which would happen at the end. Say, we only had 6 characters left from start index. If we tried to retrieve 10 characters we would have an index out of range.
At the end we join the elements of the string with the separated of new line.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
BreakInto10CharacterChunks("The quick brown fox jumped over the lazy dogs.")
End Sub
Private Sub BreakInto10CharacterChunks(input As String)
Dim output As New List(Of String)
Dim chunk As String
For StartIndex = 0 To input.Length Step 10
If StartIndex + 10 > input.Length Then
chunk = input.Substring(StartIndex, input.Length - StartIndex)
Else
chunk = input.Substring(StartIndex, 10)
End If
output.Add(chunk)
Next
Label1.Text &= vbCrLf & String.Join(vbCrLf, output)
End Sub
Be sure to look up String.SubString and String.Join to fully understand how these methods work.
https://learn.microsoft.com/en-us/dotnet/api/system.string.substring?view=netframework-4.8
and https://learn.microsoft.com/en-us/dotnet/api/system.string.join?view=netframework-4.8