asked on

Search text for a four character string counting the occurrences and location using vb.net

I have a text file that I need to search looking for a four character string. I need to count the number of occurrences and if the four character string is found get the location of each occurrence. I have to problem opening the file and reading the content. I'm just having a issue with figuring out the search.

to be more detailed I need to find the string "ISA*" that is stored in the variable "xInput" and count the occurrences and get the location of each so that it can be used later.

I've seen several examples online but I cant seem to get any to work. Any help would be appreciated.

Thanks
Mike

ChloesDad

This should do the job

        Dim StringFinder As New StringFinderClass

        StringFinder.SourceString = "I have a text file that I need to search looking for a four character string.  I need to count the number of occurrences and if the four character string is found get the location of each occurrence.   I have to problem opening the file and reading the content.   I'm just having a issue with figuring out the search."
        StringFinder.SearchString = "to"

        StringFinder.FindMatches()

        Console.WriteLine(StringFinder.Matches)

        Console.WriteLine(StringFinder.NumberOfMatches)

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Public Class StringFinderClass

    Public Property SearchString As String
    Public Property SourceString As String

    Public Property NumberOfMatches As Integer = 0
    Public Property Matches As HashSet(Of Integer) = New HashSet(Of Integer)

    Public Sub FindMatches()

        Dim Count1 As Integer
        Dim NumberOfCharacters As Integer = SourceString.Length

        For Count1 = 1 To NumberOfCharacters

            If SourceString.Substring(Count1 - 1).StartsWith(SearchString) Then

                NumberOfMatches += 1
                Matches.Add(Count1)

            End If

        Next Count1


    End Sub

End Class

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ASKER CERTIFIED SOLUTION

Fernando Soto

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Mike_Stevens

ASKER

I need to find all four (ISA*) characters together. I am using a stream reader to read the contents of the text file....

xInput = objReader.ReadToEnd()

SOLUTION

Jacques Bourgeois (James Burger)

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Fernando Soto

Hi Mike;

This code snippet will do what you need.

Imports System.Text.RegularExpressions


'' Your returned string from the StreamReader
Dim xInput = objReader.ReadToEnd()
'' Regex Pattern to search the string
Dim pattern As String = "(ISA*)"
'' Locate the matches of the pattern
Dim mc As MatchCollection = Regex.Matches(xInput, pattern)
'' Number of occurrences / Matches found
Dim totalCount As Integer = mc.Count()
'' A list of start locations for each occurrence from the begining of the string.
Dim locations As List(Of Integer) = (From m As Match In mc Select m.Index).ToList()

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Mike_Stevens

ASKER

Jacques.....your example works. Thank you. The test file that I an using to search has the value of 'ISA*' in it twice. The first occurrences is the first four characters in the file and the second is later on in the text. Your example finds the second occurrence but not the first. An example of the first line of the file is:

ISA*00*BLUE*YELLOW*GREEN......

The other occurrence is later on in the file mixed is the middle of other text.

I don't know why it wont find the first.

Fernando Soto

Hi Mike did you check out my solution?

Jacques Bourgeois (James Burger)

Just a little adjustment. IndexOf does not include the starting index, so the "i" at position 0 was not included in the search.

Simply start looking at -1 to include it:

		Dim index As Integer = -1
		Dim count As Integer

		While index < xInput.Length
			index = xInput.IndexOf("isa*", index + 1)
			If index = -1 Then Exit While
			count = count + 1
			Console.WriteLine("Occurence " & count & " at position " & index)
		End While
		Console.WriteLine("Count : " & count)

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Mike_Stevens

ASKER

Fernando....I tried yours and its nice and clean and compact but when I search for "ISA*" with the Asterisk included it does not return the correct number of occurrences . ISA* appears twice in my test file and it returns that it found four occurrences . If I remove the Asterisk it works fine but I must use the asterisk to prevent text that contain "ISA" from being returned.

Fernando Soto

Sorry Mike, the * has a special meaning in regular expressions, its meaning is to take any number of the preceding character as part of the search. To include the * as a normal character it must be escaped as shown below. Please use this statement in place of the other one.

Dim pattern As String = "(ISA\*)"

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