Question

The below code is performing following functionality which I intend to integrate into larger application.

1. Splitting large input string input by dot (.) character wherever it
   occurs in input string.
2. Storing the splitted substrings into array result[];
3. In the foreach loop , a substring is matched for occurrence of
   keyword.

4. If match occurs , starting from position of this matched substring in original input string , upto 300 characters are to be printed.

       string[] result = input.Split('.');
       foreach (string str in result)
       {
   
           //Console.WriteLine(str);
           Match m = Regex.Match(str, keyword);
           if (m.Success)
           {
               int start = input.IndexOf(str);
               if ((input.Length - start) < 300)
               {
                   Console.WriteLine(input.Substring(start, input.Length - start));
                   break;
               }
               else
               {
                   Console.WriteLine(input.Substring(start, 300)); 
                   break;
               }
           }
   

The input is in fact large amount of text and I think this should be done by regular expression. Being a novice ,I am not able to put everything together using a regular expressions .

Match keyword. Match m = Regex.Match(str, keyword);

300 characters starting from dot (.) i.e starting from matched sentence , print 300 characters "^.\w{0,300}"

What I intend to do is :

1. Search for keyword in input text.

2. Just as a match is found , start from the sentence containing the
   keyword and print upto 300 characters from input string.

   How should I proceed ? Please help .

Answer 1

If I got it right, all you need to do is find your keyword and capture all that follows until you find first dot or reach maximum number of characters:

@"keyword([^\.]{0,300})"

C# code:

var regex = new Regex(@"keyword([^\.]{0,300})");

foreach (Match match in regex.Matches(input))
{
   var result = match.Groups[1].Value;
   
   // work with the result
}