CODEWITHSUNDEEP
vb.netvb6vb6-migration
Stefan van de Laarschot
Stefan van de Laarschot

Reputation: 2163

VB6 Code to VB.NET

I have a problem translating VB6 To VB.NET i need this translated for the new functionality.

I've tried to translate VB6 code to VB.net but it failed maybe someone can help me out here

I don't know what ReDim intKeyChars(1 To intKeyLen) should look like the rest i think can be copy paste to VB.NET. VB6 behaves different from VB.NET in some cases.

  Public Function EnDecrypt( _
  ByVal strInputText As String, _
  ByRef strOutputText As String _
  ) As Boolean

On Error Resume Next
  On Error GoTo ErrorHandler

  ' Private vars
  Dim intKeyChars()   As Long
  Dim intKeyChr       As Long
  Dim intKeyIndex     As Long
  Dim intKeyLen       As Long
  Dim intTextLen      As Long
  Dim intCounter      As Long
  Dim strInputKey     As String

  ' Set input key
  strInputKey = "TEST1290"

  ' Move key chars into an array of long to speed up code
  intTextLen = Len(strInputText)
  intKeyLen = Len(strInputKey)
  intKeyIndex = intKeyLen

  If (intKeyLen = 0) Or (intTextLen = 0) Then
    GoTo ErrorHandler
  End If

  ReDim intKeyChars(1 To intKeyLen)

  For intCounter = 1 To intKeyLen
    intKeyChars(intCounter) = Asc(Mid(strInputKey, intCounter, 1))
  Next intCounter

  For intCounter = 1 To intTextLen

    ' Get the next char in the password
    intKeyChr = intKeyChars(intKeyIndex)

    ' EnDecrypt one character in the string
    Mid(strInputText, intCounter, 1) = Chr(Asc(Mid(strInputText, intCounter, 1)) Xor intKeyChr)

    ' Modify the character in the password (avoid overflow)
    intKeyChars(intKeyIndex) = (intKeyChr + 32) Mod 126

    ' Prepare to use next char in the password
    intKeyIndex = (intKeyIndex Mod intKeyLen) + 1

  Next intCounter

  ' Return values
  strOutputText = strInputText
  EnDecrypt = True

  Exit Function

ErrorHandler:

  ' Return values
  strOutputText = vbNullString
  EnDecrypt = False

End Function

Upvotes: 0

Views: 1097

Answers (2)

R.J. Dunnill
R.J. Dunnill

Reputation: 2089

The ReDim statement can look like this: ReDim intKeyChars(intKeyLen)

VB.NET arrays are always lower-bounded with zero, and thus ReDim only takes one parameter, the upper bound. Note that unlike C#, the upper bound index will be UBound(intKeyChars), not UBound(intKeyChars)-1, so the rest of the code should work. (intKeyChars element zero will be unused.)

Upvotes: 0

David
David

Reputation: 6131

Let's step through what the code actually does:

ReDim intKeyChars(1 To intKeyLen)

The ReDim keyword literally re-declares the intKeyChars variable where as the 1 to intKeyLen specifies that you want the bottom of the array to start at an index of 1 (which was common in legacy VB code) and the top of the array to end at an index of whatever the value of intKeyLen is.

There are some things that you'll need to adjust. Firstly, arrays cannot have an index of 1 in Visual Basic .NET, they must have an index of 0.

Secondly, the reason why legacy VB code used the ReDim statement to add items to an array was because there was no simple method of adding or removing items to a collection, you literally had to reallocate the memory and add or remove any values at that time. Luckily in Visual Basic .NET we have the List(Of T) collection that gives us built in methods such as Add, AddRange, Insert, Remove, RemoveAt, and RemoveRange. But after looking at the code some more, the original legacy code should've just declare the array with the specified upper-bounds equal to the String's length in the first place (no need to ReDim the array each time).

So in your case, the updated code may look something like this:

Dim intKeyChars(strInputKey.Length - 1) As Integer
For intCounter As Integer = 0 To intKeyChars.Length - 1
    intKeyChars(intCounter) = Asc(strInputKey(intCounter))
Next

Upvotes: 3

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