how to count distinct strings inside string vb.net

Question

I am working on a vb.net utility and have run into a need to find all the distinct strings inside a string.

So basically I will have a string that will look like this. 1.875{0};10;0.25|1.875;9;0.25|{2}1.875;1.875;0.25|14.125;{1}1.875;0.25|{0}14.125;16.125{1};0.25|1.875;{0}16.125;0.25|1.875;9;0.25{2}|1.875;8;0.25

So you can see I have these chars inside the string {0}, {1}, {2}

There are however multiples of each "placeholder" so to speak.

So i need help writing a function that will take string string above and return a count of 3 in this example, because there are 3 distinct placeholders in the source string. It would kind of mimick the distinct command in sql.

I'm sure this uses some kind of regex but I can't wrap my head around it to retrieve only the distinct ones. Not all the multiples.

Any help is appreciated. Thanks in Advance.

Bob Mc · Accepted Answer · 2013-02-16 20:05:55Z

2

Using regular expressions and a little bit of LINQ you can achieve the desired effect

Imports System.Text.RegularExpressions
Imports System.Linq

Private Function CountPlaceholders(source As String) As Integer
    Dim matches As MatchCollection = Regex.Matches(source, "{[0-9]+}")
    Return matches.Cast(Of Match)().Select(Function(m) m.Value).Distinct().Count()
End Function

First, find all the placeholders using a fairly straightforward regular expression. The + after the [0-9] numeric search will find one or more occurrences of a number so will find placeholders 0 through n.

The next line is what counts the distinct occurrences. Each item in the matches MatchCollection has to be cast to Match in order for the LINQ-to-Objects extensions to operate. After that, you select the Value property of the Match object, filter the distinct values, and count them.

edited Feb 16, 2013 at 20:05

answered Feb 16, 2013 at 18:29

Bob Mc

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1 Comment

joeb Over a year ago

Awesome! Thank you very much. Taught me something new.

shf301 · Accepted Answer · 2013-02-16 18:02:16Z

0

Yes you can use the regex {\d+} to do the match, but you are correct that will not give you a distinct list. But you can loop over the Match collection returned by Regex.Matches, extract the Value and use the Distinct Linq method to get a list of the distinct entries.

answered Feb 16, 2013 at 18:02

shf301

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