How to split a string into a fixed length string array?

Question

I have a long string like this

dim LongString as String = "123abc456def789ghi"

And I want to split it into a string array. Each element of the array should be in 3 characters length

For example,

Dim LongArray(5) As String
LongArray(0)  = "123"
LongArray(1)  = "abc"
LongArray(2)  = "456"
LongArray(3)  = "def"
LongArray(4)  = "789"
LongArray(5)  = "ghi"

How do I split it using VB.net code?

What should happen if the string length is not a multiple of 3? — Jon Skeet, Sep 11 '11 at 07:54
See http://msdn.microsoft.com/en-us/library/6x627e5f(v=vs.80).aspx — BlackJack, Sep 11 '11 at 07:55
@BlackJack: I have tried it. But what is the `delimiter` value for my case? — Yoga Fire, Sep 11 '11 at 07:58
Possible duplicate of http://stackoverflow.com/questions/1450774/c-split-a-string-into-equal-chunks-each-of-size-4 — Paolo Moretti, Sep 11 '11 at 08:06
@Yoga Fire: So the method can throw an exception if it's not? — Jon Skeet, Sep 11 '11 at 08:09
@Jon Skeet: The string length will be checked before the split operation, so no need for exception — Yoga Fire, Sep 11 '11 at 08:12
@Yoga Fire: I would personally prefer to check the arguments within the method, but there we go... — Jon Skeet, Sep 11 '11 at 08:14

Aaron · Answer 1 · 2011-09-11T08:13:24.843

6

You could use LINQ like so:


' VB.NET
Dim str = "123abc456def789ghij"
Dim len = 3
Dim arr = Enumerable.Range(0, str.Length / len).Select (Function(x) str.Substring(x * len, len)).ToArray()


// C#
var str = "123abc456def789ghij";
var len = 3;
var arr = Enumerable.Range(0, str.Length / len).Select (x => str.Substring(x * len, len)).ToArray();

Note this will only take complete occurrences of length (i.e. 3 sets in a string 10 characters long).

edited Sep 11 '11 at 08:13

answered Sep 11 '11 at 08:01

Aaron

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Thanks for the answer, but LINQ is not supported for .Net v1.1 – Yoga Fire Sep 11 '11 at 08:03
4

@Yoga Perhaps you should have written you were still using ancient instruments! – xanatos Sep 11 '11 at 08:06
@xanatos in his defense it has a .net1.1 tag to the question. – chrissie1 Sep 11 '11 at 08:09
@chrissie1: Only since xanatos added it. – Jon Skeet Sep 11 '11 at 08:13

score 2 · Accepted Answer · answered Sep 11 '11 at 08:06

This could work.

 Module Module1

    Sub Main()
        Dim LongString As String = "123abc456def789ghi"
        Dim longlist As New List(Of String)
        For i As Integer = 0 To Convert.ToInt32(LongString.Length / 3) - 1
            longlist.Add(LongString.Substring(i * 3, 3))
        Next
        For Each s As String In longlist
            Console.WriteLine(s)
        Next
        Console.ReadLine()
    End Sub

End Module

And this should work in .Net 1.1

Module Module1

    Sub Main()
        Dim LongString As String = "123abc456def789ghi"
        Dim longlist(Convert.ToInt32(LongString.Length / 3) - 1) As String
        For i As Integer = 0 To Convert.ToInt32(LongString.Length / 3) - 1
            longlist(i) = (LongString.Substring(i * 3, 3))
        Next
        For i As Integer = 0 To Convert.ToInt32(LongString.Length / 3) - 1
            Console.WriteLine(longlist(i))
        Next
        Console.ReadLine()
    End Sub

End Module

Jon Skeet · Answer 3 · 2011-09-11T09:04:37.123

This C# code should work:

public static string[] SplitByLength(string text, int length)
{
    // According to your comments these checks aren't necessary, but
    // I think they're good practice...
    if (text == null)
    {
        throw new ArgumentNullException("text");
    }
    if (length <= 0)
    {
        throw new ArgumentOutOfRangeException("length");
    }
    if (text.Length % length != 0)
    {
        throw new ArgumentException
            ("Text length is not a multiple of the split length");
    }
    string[] ret = new string[text.Length / length];
    for (int i = 0; i < ret.Length; i++)
    {
        ret[i] = text.Substring(i * length, length);
    }
    return ret;
}

Reflector converts that to VB as:

Public Shared Function SplitByLength(ByVal [text] As String, _
                                      ByVal length As Integer) As String()
    ' Argument validation elided
    Dim strArray As String() = New String(([text].Length \ length)  - 1) {}
    Dim i As Integer
    For i = 0 To ret.Length - 1
        strArray(i) = [text].Substring((i * length), length)
    Next i
    Return strArray
End Function

It's possible that that isn't idiomatic VB, which is why I've included the C# as well.

@Jon Why is reflector convertin integer division to non-integer (VB.NET) divisions? Shouldn't it convert ``\`` to `/`? It doesn't know the prereq that the number are always divisible by 3. — xanatos, Sep 11 '11 at 09:00
@Jon Told by one of the four persons with the gold badge of VB.NET :-) It was more a question of "is this a bug of the reflector or what" — xanatos, Sep 11 '11 at 09:10

score 1 · Answer 4 · edited Oct 15 '12 at 14:02

1

I'm splitting the string by 35.

var tempstore ="12345678901234567890123456789012345";

for (int k = 0; k < tempstore.Length; k += 35) {
    PMSIMTRequest.Append(tempstore.Substring(k,
      tempstore.Length - k > 35 ? 35 : tempstore.Length - k));
    PMSIMTRequest.Append(System.Environment.NewLine);
}

messagebox.Show(PMSIMTRequest.tostring());

edited Oct 15 '12 at 14:02

Eonasdan

7,563
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answered Oct 15 '12 at 13:53

vangli

53
1
6

score 0 · Answer 5 · edited Jan 30 '14 at 15:59

Last array is missing:

Public Function SplitByLength(ByVal text As String, _
                                  ByVal length As Integer) As String()

  ' Argument validation elided
  Dim strArray As String() = New String((text.Length \ length)  - 1) {}
  Dim i As Integer
  For i = 0 To text.Length - 1
      strArray(i) = text.Substring((i * length), length)
  Next i

  ' Get last array:
  ReDim Preserve strArray(i)
  strArray(i) = text.Substring(i * length)
  Return strArray
End Function

score 0 · Answer 6 · answered Jun 05 '17 at 05:58

I have added some more logic to @jon code. This will work perfectly for the string which has length less than length passed.

 Public Shared Function SplitByLength(ByVal [text] As String, ByVal length As Integer) As String()

    Dim stringLength = text.Length
    Dim arrLength As Integer = ([text].Length \ length) - 1 + IIf(([text].Length 
                                             Mod length) > 0, 1, 0)
    Dim strArray As String() = New String(arrLength) {}

    Dim returnString As String = ""
    Dim i As Integer
    Dim remLength As Integer = 0

    For i = 0 To strArray.Length - 1
      remLength = stringLength - i * length
      If remLength < length Then
        strArray(i) = [text].Substring((i * length), remLength)
      Else
        strArray(i) = [text].Substring((i * length), length)
      End If
    Next i

       Return  strArray
END FUNCTION

score 0 · Answer 7 · edited Jul 08 '20 at 08:11

0

This is my solution:

Function splitN(str As String, n As Integer) As String()
  For i = 0 To Len(str) Step n + 1
    Try
      str = str.Insert(i + n, "|")
    Catch
    End Try
  Next
  Return str.Split("|")
End Function

You can call it like: splitN("abc123def456frg987ef", 3)

edited Jul 08 '20 at 08:11

piraces

1,320
2
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answered Jul 07 '20 at 18:07

VuongH

1

score 0 · Answer 8 · answered Sep 11 '11 at 08:22

Dim LongString As String = "1234567"

Dim LongArray((LongString.Length + 2) \ 3 - 1) As String

For i As Integer = 0 To LongString.Length - 1 Step 3
    LongArray(i \ 3) = IF (i + 3 < LongString.Length, LongString.Substring(i, 3), LongString.Substring(i, LongString.Length - i))           
Next

For Each s As String In LongArray
    Console.WriteLine(s)
Next

There are some interesting parts, the use of the \ integer division (that is always rounded down), the fact that in VB.NET you have to tell to DIM the maximum element of the array (so the length of the array is +1) (this is funny only for C# programmers) (and it's solved by the -1 in the dim), the "+ 2" addition (I need to round UP the division by 3, so I simply add 2 to the dividend, I could have used a ternary operator and the modulus, and in the first test I did it), and the use of the ternary operator IF() in getting the substring.

How to split a string into a fixed length string array?

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