Using Regex to replace a value in a string from a list of items in array

Question

I'm not sure I'm asking what is possible. I have a situation

Dim animalList as string = "Dog|Cat|Bird|Mouse"
Dim animal_story_string as string = "One day I was walking down the street and I saw a dog"
Dim hasAnAnimalonList as Boolean 
Dim animals() as String =   animalList.Split("|")
Dim regex As New Regex("\b" & String.Join("\b|\b", animals) & "\b", RegexOptions.IgnoreCase)
If regex.IsMatch(animal_story_string) Then
   hasAnAnimalonList = True
  'Here I would like to replace/format the animal found with HTML bold tags so it would look 
   like  "One day I was walking down the street and I saw a <b>dog</>"
End If

In the past I would loop each value in the animalList and if a match is found replace it at that time. Like

     For Each animal As string in animals
      ' I would replace every animal in the list
      ' If Cat and Birds and Mouse were not in the string it did not matter 
        animal_story_string = animal_story_string.Replace(animal,"<b>" + animal + "</b>" 
     Next

Is there a way to do it using a Regex function?

dr.null · Accepted Answer · 2022-07-03 03:09:45Z

1

Is there a way to do it using a Regex function?

Yes, call Regex.Replace method and split the Dog|Cat|Bird|Mouse string to join the result and create the regex pattern as shown below, you can replace the matches in one line using a MatchEvaluator function.

Dim animalList = "Dog|Cat|Bird|Mouse"
Dim regexPattern = String.Join("|", animalList.Split("|"c).Select(Function(x) $"\b{x}\b"))
Dim animal_story_string = "One day I was walking down the street and I saw a dog or maybe a fat cat! I didn't see a bird though."
Dim hasAnAnimalonList = Regex.IsMatch(animal_story_string, regexPattern, RegexOptions.IgnoreCase)

If hasAnAnimalonList Then
    Dim replace = Regex.Replace(
        animal_story_string,
        regexPattern,
        Function(m) $"<b>{m.Value}</b>", RegexOptions.IgnoreCase)

    Console.WriteLine(replace)
End If

Writes in the console:

One day I was walking down the street and I saw a <b>dog</b> or maybe a fat <b>cat</b>! I didn't see a <b>bird</b> though.

... and in HTML renderer...

One day I was walking down the street and I saw a dog or maybe a fat cat! I didn't see a bird though.

edited Jul 3, 2022 at 3:09

answered Jul 3, 2022 at 1:14

dr.null

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5 Comments

Bill Over a year ago

This looks great-- I'll give it a try Thanks Regex is extremely powerful

dr.null Over a year ago

@Bill I've fixed the regex pattern to not match for example dog in hotdog...etc

Bill Over a year ago

Thank you. I actually have a use for both situations. As you can imagine, the Cat's and Dog's are just a simplified example. I'll push my luck and ask do you have a simple way for Regex to handle and &? So if I wanted to format in a sentence "Bob & Mary" but the list has "Bob and Mary" . Currently in the sentence I test if & exists and if it does I add to the list an additional item with replacing "and" with "&". I highlight format if a researcher publishes using their department of "Cell and Molecular Pharmacology" or "Cell & Molecular Pharmacology". Have no control over entry

dr.null Over a year ago

@Bill You are welcome. I'm not sure if you mean something like this or an explicit one like this. It Depends, maybe a string method call like: Dim s = "Cell and Molecular Pharmacology".Replace("and", "&") could be more efficient in some cases. Keep it simple.

Bill Over a year ago

Yup-- I'm doing the replace and that's working fine. Very similar to matching joined combined names with or without hyphens like: Smith Jones and Smith-Jones same person just a different input. Thanks for your help

Patrick Hume · Accepted Answer · 2022-07-03 01:22:49Z

1

I think

/(?:^|(?<= ))(Dog|Cat|Bird|Mouse)(?:(?= )|$)/i

or even

/\b(Dog|Cat|Bird|Mouse)\b/i

See: https://regex101.com/r/V4Uhg7/1

will do what you want?

edited Jul 3, 2022 at 1:22

answered Jul 3, 2022 at 1:08

Patrick Hume

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