Extract numbers from an AlphaNumeric string

Question

I have an alphanumeric string like sdff45hg589>@#DF456&<jk778P&&FHJ75, of which I want to extract only the numbers, without using regex or any other functions.

Dim input As String = "sdff45hg589>@#DF456&<jk778P&&FHJ75"
Dim output As String = New String((From c As Char In input Select c Where Char.IsDigit(c)).ToArray())
MsgBox(output) 'Display the output 

The message box will display 4558945677875.

For extracting letters from the same string, I use the following:

 Dim input As String = "sdff45hg589>@#DF456&<jk778P&&FHJ75"
 Dim output As String = New String((From c As Char In input Select c Where Char.IsLetter(c)).ToArray())
 MsgBox (output)

Is this a better way to extract both?

• rolfl: This appears to be copied from: stackoverflow.com/a/24650229/1305253

Answer 1

If you want to extract both at the same time (I don't know if it is a requirement, it isn't clear in the question) you should iterate once through each character to place them in different lists.

 Dim input As String = "sdff45hg589>@#DF456&<jk778P&&FHJ75"
 Dim characters As List(Of Char) = New List(Of Char)()
 Dim numbers As List(Of Char) = New List(Of Char)()
 For Each c As Char In input
 If (Char.IsNumber(c)) Then
 numbers.Add(c)
 ElseIf (Char.IsLetter(c)) Then
 characters.Add(c)
 End If
 Next
'Do whatever you have to do here

Edit

As pointed out @mjolka, since the goal of the user is to show the splitted numbers and letters, a StringBuilder would be more appropriate. Here is my updated answer :

 Dim input As String = "sdff45hg589>@#DF456&<jk778P&&FHJ75"
 Dim characters As StringBuilder = New StringBuilder()
 Dim numbers As StringBuilder = New StringBuilder()
 For Each c As Char In input
 If (Char.IsNumber(c)) Then
 numbers.Append(c)
 ElseIf (Char.IsLetter(c)) Then
 characters.Append(c)
 End If
 Next
'Do whatever you have to do here

• mjolka: I think a StringBuilder would be better than a List(Of Char). It makes the intention clearer and you can just call numbers.ToString().
• IEatBagels: That is totally true, I'll update my answer

Answer 2

you can do this with a very simple regex replace.

Dim match = Regex.Replace("sdff45hg589>@#DF456&<jk778P&&FHJ75", "\D", "")

non-digits is "\D", and then replace it with empty string.

I ran for above data it works fine.

• Sujith Karivelil: But how to extract letters using this?
• Paritosh: use \d to remove digit.