Replacing Characters in an Array in VB.NET

Question

I am trying to create a deciphering program which takes the entire English alphabet and shifts the letters' positioning to the left at one increment at a time. I have created a character array for this and I have got the shifting part to work. So, the index of each character in the array changes each time a shift is made. I also created an identical character array which does not shift so it has something to compare to.

Once the shift is made, I have textbox1 output into textbox2 which replaces the letters to their now corresponding letters based on the index of the first character array. For instance, "ABC" is now "DEF". The problem I am having is upon replacing the characters, it will replace them again because their state was changed previously. For example, I changed "A" to "B". Then I move on to changing "B" to "C". But since the "A" was changed to a "B", it is changed again to a "C". I realize doing a For Each Loop caused this to happen so I took it out of a loop and it still does it. I even tried putting a break in the code such as GOTO but that just stops the loop after changing the first letter.

Here is my code:

Private Sub cryptshift()
    'SHIFTING ALL CHARACTERS IN ARRAY ONE SPACE TO THE LEFT
    Dim temporaryStorageA As [String] = charArray(0)
    Dim temporaryStorageB As [String]() = New [String](charArray.Length - 1) {}

    For i As Integer = 1 To charArray.Length - 1
        temporaryStorageB(i - 1) = charArray(i)
        charArray(i - 1) = temporaryStorageB(i - 1)
    Next
    charArray(charArray.Length - 1) = temporaryStorageA

    'CLEARING LABEL54 AND REALIGNING ARRAY TO LABEL53
    Label54.Text = Nothing
    For Each c In charArray
        Label54.Text = Label54.Text & c & "-"
    Next

    'DECIPHERING
    Dim mess As String = TextBox1.Text
    Dim result As String = ""
    For i As Integer = 0 To mess.Length - 1
        Dim c As Char = mess(i)
        Dim itemindex As Integer = Array.IndexOf(charArray2, c)

    '**This IF Statement allows letters to be deciphered but also allows other characters such as punctuation, numbers and spaces to go through without any altering.**
        If charArray2.Contains(c) Then
            result &= charArray(itemindex)
        Else
            result &= c
        End If

    Next
    TextBox2.Text = result


End Sub

Instead of using a For Each loop, you should be using a For loop to process all the characters by their position in the array. — Pikoh
– Pikoh, Commented Oct 23, 2017 at 8:06
Did you try to introduce a new variable that is filled from the for each loop instead of changing the original? — Noixes
– Noixes, Commented Oct 23, 2017 at 8:08
No. I tried changing each letter in the string which is equal to the text in textbox1. — BuddyRoach
– BuddyRoach, Commented Oct 23, 2017 at 8:14

the_lotus · Accepted Answer · 2017-10-23 12:32:12Z

1

Your problem is the .Replace. You should change only the current character. Here, I'm creating a new string with the result.

Dim mess As String = TextBox1.Text
Dim result As String = ""
For i As Integer = 0 To mess.length-1
    Dim c As Char = mess(I)
    Dim itemindex As Integer = Array.IndexOf(charArray2, c)
    result &= charArray(itemindex)
Next

You could then use a string building.

answered Oct 23, 2017 at 12:32

the_lotus

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3 Comments

BuddyRoach Over a year ago

Thanks! This worked. But now if my message is too long, it crashes and I get this error: Index was outside the bounds of the array. I will add my shifting code above to show you my method.

BuddyRoach Over a year ago

Ok. I figured it out. It was spaces (or any character that was not in the array) that was throwing an error. I fixed it by using an IF statement, thus allowing all other characters through to the newly built string. But only letters are altered. Thanks again. Sorry for the second comment but it won't allow me to edit the last one for some odd reason.

the_lotus Over a year ago

@BuddyRoach happy to hear that you figured it out!

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