Is there a function to get string between 2 string in vb.net

Question

In a failed attempt to teach my daughter programming I taught her to make this

Public Shared Function getBetween(strSource As String, startSearchIndex As Integer, startSearch As String, endSearch As String) As (nextIndex As Integer, Content As String)
    Dim IndexStart = strSource.IndexOf(startSearch, startSearchIndex)
    Dim startContent = IndexStart + startSearch.Length
    Dim indexEnd = strSource.IndexOf(endSearch, startContent)
    Dim content = strSource.Substring(startContent, indexEnd - startContent)
    Dim nextIndex = indexEnd + endSearch.Length
    Return (nextIndex, content)

End Function

We know what the function does. Get strings between 2 strings in a big string.

I wonder if there is a built in function for this?

Samples:

If I use this test function

Public Shared Sub test(txt As TextBox)
    Dim source = "0123456789([012345])0123456789([ABCDEF])0123456789([GHIJK])"
    txt.Text += source + System.Environment.NewLine
    getBetween3Times(txt, source, "(", ")")
    getBetween3Times(txt, source, "([", "])")
    getBetween3Times(txt, source, "[", "]")
End Sub

Private Shared Sub getBetween3Times(txt As TextBox, source As String, startsearch As String, endsearch As String)
    Dim result = getBetween(source, 0, startsearch, endsearch)
    txt.Text += result.Content + System.Environment.NewLine
    result = getBetween(source, result.nextIndex, startsearch, endsearch)
    txt.Text += result.Content + System.Environment.NewLine
    result = getBetween(source, result.nextIndex, startsearch, endsearch)
    txt.Text += result.Content + System.Environment.NewLine
End Sub

It will produce

0123456789([012345])0123456789([ABCDEF])0123456789([GHIJK])
[012345]
[ABCDEF]
[GHIJK]
012345
ABCDEF
GHIJK
012345
ABCDEF
GHIJK

But i can give you already the answer, if it's working (it's looks so) then it's the closest you can get to "built in function". — Tim Schmelter
– Tim Schmelter, Commented Apr 1, 2021 at 12:54

Tim Schmelter · Accepted Answer · 2021-04-01 13:04:00Z

1

No, there is no built-in method, or yes, there are, but you use them already.

Maybe you want to handle invalid input. Also, your method includes the search-token, but you want the text between, so maybe this one is little bit better:

Public Shared Function GetTextBetween(strSource As String, startSearchIndex As Integer, startSearch As String, endSearch As String) As (nextIndex As Integer, Content As String)
    If startSearchIndex < 0 Orelse startSearchIndex >= strSource.Length Then Throw New ArgumentException(Nameof(startSearchIndex))
    Dim index = strSource.IndexOf(startSearch, startSearchIndex)
    If index = -1 Then Return (-1, Nothing)
    index += startSearch.Length
    Dim endIndex = strSource.IndexOf(endSearch, index+1)
    If endIndex = -1 Then Return (-1, Nothing)
    Dim content = strSource.Substring(index, endIndex - index)
    Return (endIndex + endSearch.Length, content)
End Function

Dim sampleText = "It is the end of the world"
Dim result = GetTextBetween(sampleText, 0, "is ", " of") ' should be "the end"

answered Apr 1, 2021 at 13:04

Tim Schmelter

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1 Comment

Vibi Chrisbud Over a year ago

Thanks. My code won't return the search token though. I tested it. Also the search strings may be longer than 1 character

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