Count total occurences of elements from string array in a text

Question

I have a

public static string[] words = {"word1","word2","word3"};

I want to count occurences of word1 + occurences of word2+ occurences of word3 in a string.

I tried

Regex.Matches(string, "word1").Count 

which works fine for a single word but i don't know how to search for all strings. I dont't want to use foreach because the array "words" can contains up to 25 strings. Thanks.

Answer 1

This is a more versatile way to do this.
Regex gives you more control over the context of the words it finds.
And, I'm guessing it's a lot faster, since it does it all in one shot
without a lot of primitives manipulation.

string[] words = { "word1", "word2", "word3" };
Regex rx = new Regex(   @"(?is)(?:.*?\b(" + string.Join("|", words) +   @")\b)+");

string strin = "There are some word3 and more words and word1 and more word3, again word1";

Match m = rx.Match( strin );
if ( m.Success )
    Console.WriteLine("Found {0} words", m.Groups[1].Captures.Count);

Output

Found 4 words

---

The regex above uses the word boundary \b.
Alternative boundary choice: Whitespace (?<!\S) (?!\S)