Find a keyword taken from a string and look for it in a list of string

Question

I have a list of strings which contain 4 items:

Orange Lemon Pepper Tomato

Also, I have a String str which has a sentence:

Today, I ate a tomato and an orange.

1) How can I check that str has some keywords from list? without considering upper or lower case letters, basically capturing anything that matches?

I tried this but it doesn't work because it will look for the same words. list.Contains(str)

Also Dim result As String() = list.FindAll(str, Function(s) s.ToLower().Contains(str)) but also didn't work.

2) What if the word tomato was tomatoes in str, how can I still detect the tomato part and discard the es part?

Any suggestions or ideas ?

score 3 · Accepted Answer · edited Dec 18 '12 at 00:48

3

var list = new string[] { "Orange", "Lemon", "Pepper", "Tomato" };
var str = "Today, I ate a tomato and an orange.";

With LINQ and Regular Expressions you can check if string contains any keyword:

list.Any(keyword => Regex.IsMatch(str, Regex.Escape(keyword), RegexOptions.IgnoreCase));

Or get matched keywords:

var matched = list.Where(keyword =>
                Regex.IsMatch(str, Regex.Escape(keyword), RegexOptions.IgnoreCase));
// "Orange", "Tomato"

BTW this will match both tomatoes and footomato. If you need to match start of word, then search pattern should be changed a little: @"(^|\s)" + keyword

edited Dec 18 '12 at 00:48

jessehouwing

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answered Dec 11 '12 at 16:07

Sergey Berezovskiy

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Don't forget to call Regex.Escape on your keywords. Should you have a keyword with a special Regex character in it, you won't get a runtime exception... So Regex.IsMatch(str, Regex.Escape(keyword)....). – jessehouwing Dec 18 '12 at 00:36

score 3 · Answer 2 · edited Dec 18 '12 at 00:46

3

If case sensitivity isn't an issue you could do this:

List<string> test = new List<string>();
test.Add("Lemon");
test.Add("Orange");
test.Add("Pepper");
test.Add("Tomato");

string str = "Today, I ate a tomato and an orange.";

foreach (string s in test)
{
      // Or use StringComparison.OrdinalIgnoreCase when cultures are of no issue.
      if (str.IndexOf(s, StringComparison.CurrentCultureIgnoreCase) > -1)
      {
          Console.WriteLine("Sentence contains word: " + s);
      }
}

Console.Read();

edited Dec 18 '12 at 00:46

jessehouwing

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answered Dec 11 '12 at 16:08

DGibbs

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First: IndexOf > -1, 0 can be the first position in the string. Second: Use str.IndexOf(s, StringComparison.IgnoreCase) instead. – jessehouwing Dec 18 '12 at 00:45
Thanks for the edit, wasn't aware of `CurrentCultureIgnoreCase` :) – DGibbs Dec 18 '12 at 17:07

score 2 · Answer 3 · answered Dec 11 '12 at 16:11

2

Regex reg = new Regex("(Orange|lemon|pepper|Tomato)", RegexOptions.IgnoreCase | RegexOptions.Singleline);
MatchCollection mc = reg.Matches("Today, I ate tomatoes and an orange.");
foreach (Match mt in mc)
{
    Debug.WriteLine(mt.Groups[0].Value);
}

answered Dec 11 '12 at 16:11

urlreader

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PiousVenom · Answer 4 · 2012-12-11T16:12:31.107

1

With the list.Contains(str), you're checking if that list contains that whole string. What you need to do to check that str has words in the list is something like this:

foreach(var s in list)
{
     if(str.ToLower().Contains(s.ToLower()))
     {
          //do your code here
     }
}

That will iterate through your list, and check your str to see if it's in there. It will also solve your question 2. Since tomato is part of tomatoes, it will pass that check. The ToLower() portion makes everything lower case, and is commonly used when you want to ignore case.

edited Dec 11 '12 at 16:12

answered Dec 11 '12 at 16:06

PiousVenom

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Don't use ToLower for string comparisons, use ToUpperInvariant or ToUpper(CultureInfo.CurrentCulture) instead. See: http://stackoverflow.com/questions/2801508/what-is-wrong-with-tolowerinvariant or use IndexOf(StringComparisonType)>-1 http://msdn.microsoft.com/en-us/library/ms224425(v=vs.95).aspx – jessehouwing Dec 18 '12 at 00:41

Steve · Answer 5 · 2012-12-11T16:18:52.900

1

Private Function stringContainsOneOfMany(ByVal haystack As String, ByVal needles As String()) As Boolean
    For Each needle In needles
        If haystack.ToLower.Contains(needle.ToLower) Then
            Return True
        End If
    Next
    Return False
End Function

to use:

    Dim keywords As New List(Of String) From {
        "Orange", "Lemon", "Pepper", "Tomato"}
    Dim str As String = "Today, I ate a tomato and an orange"
    If stringContainsOneOfMany(str, keywords.ToArray) Then
        'do something
    End If

edited Dec 11 '12 at 16:18

answered Dec 11 '12 at 16:11

Steve

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Don't use ToLower for string comparisons, use ToUpperInvariant or ToUpper(CultureInfo.CurrentCulture) instead. See: http://stackoverflow.com/questions/2801508/what-is-wrong-with-tolowerinvariant or use IndexOf(StringComparisonType)>-1 http://msdn.microsoft.com/en-us/library/ms224425(v=vs.95).aspx – jessehouwing Dec 18 '12 at 00:41

score 1 · Answer 6 · answered Dec 11 '12 at 16:11

1

    Dim str As String = "Today, I ate a tomato and an orange"
    Dim sWords As String = "Orange Lemon Pepper Tomato"
    Dim sWordArray() As String = sWords.Split(" ")

    For Each sWord In sWordArray

        If str.ToLower.Contains(sWord.ToLower) Then
            Console.WriteLine(sWord)
        End If

    Next sWord

answered Dec 11 '12 at 16:11

Ciarán

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Don't use ToLower for string comparisons, use ToUpperInvariant or ToUpper(CultureInfo.CurrentCulture) instead. See: http://stackoverflow.com/questions/2801508/what-is-wrong-with-tolowerinvariant or use IndexOf(StringComparisonType)>-1 http://msdn.microsoft.com/en-us/library/ms224425(v=vs.95).aspx – jessehouwing Dec 18 '12 at 00:43

Find a keyword taken from a string and look for it in a list of string

6 Answers6