C# - How to Return a Substring Between Two Strings

Here is a non-RegEx solution for returning a substring between two strings in C#. I have also added a function for retrieving multiple occurrences which outputs as a List of strings.

The parameters called: includeFrom and includeUntil allow you to append the from and until fields to the result.


Usage:

Code Snippet

1. // Example for one occurrences
2. // This extracts 'Message Here' from this example chat log
3. string message = "[12th July 2014] Message Here (Sent by Sean)".Substring(from: "]", until: "(", includeFrom: false, includeUntil: false);
5. // Example for multiple occurances
6. // This extracts all of the names which are enclosed between single quotes
7. List<string> listOfNames = "'sean' random text 'dave' 355353 'jane' some text here 'tom'".SubstringAll(from: "'", until: "'");

End of Code Snippet

The Code:

Code Snippet

1. /// <summary>
2. /// Returns a substring between two anchor strings
3. /// If from is null - Start of the string until the Second anchor
4. /// If until is null - First anchor to the end of the string is returned
5. /// </summary>
6. /// <param name="this">Input string</param>
7. /// <param name="from">An optional string to search after</param>
8. /// <param name="until">An optional string to search before</param>
9. /// <param name="includeFrom">Include from in the result</param>
10. /// <param name="includeUntil">Include until in the result</param>
11. /// <param name="comparison">An optional comparison for the search</param>
12. /// <returns>A substring based on the search</returns>
13. public static string Substring(this string @this, string from = null, string until = null, bool includeFrom = false, bool includeUntil = false, StringComparison comparison = StringComparison.InvariantCulture)
14. {
15.     var fromLength = (from ?? string.Empty).Length;
16.     var startIndex = !string.IsNullOrEmpty(from)
17.         ? @this.IndexOf(from, comparison) + fromLength
18.         : 0;
19.  
20.     if (startIndex < fromLength) { return string.Empty; }
21.  
22.     var endIndex = !string.IsNullOrEmpty(until)
23.     ? @this.IndexOf(until, startIndex, comparison)
24.     : @this.Length;
25.  
26.     if (endIndex < 0) { return string.Empty; }
27.  
28.     if (includeFrom) // Do these AFTER start and end have been calculated
29.         startIndex -= from.Length;
30.     if (includeUntil)
31.         endIndex += until.Length;
32.  
33.     return @this.Substring(startIndex, endIndex - startIndex);
34. }
35.  
36. /// <summary>
37. /// Returns a List of substrings between two anchor strings
38. /// If from is null - Start of the string until the Second anchor
39. /// If until is null - First anchor to the end of the string is returned
40. /// </summary>
41. /// <param name="this">Input string</param>
42. /// <param name="from">An optional string to search after</param>
43. /// <param name="until">An optional string to search before</param>
44. /// <param name="includeFrom">Include from in the result</param>
45. /// <param name="includeUntil">Include until in the result</param>
46. /// <param name="skipEmptyResults">If empty results are found, then they are not added to the result set.</param>
47. /// <param name="comparison">An optional comparison for the search</param>
48. /// <returns>A List of substrings based on the search</returns>
49. public static List<string> SubstringAll(this string @this, string from = null, string until = null, bool includeFrom = false, bool includeUntil = false, bool skipEmptyResults = true, StringComparison comparison = StringComparison.InvariantCulture)
50. {
51.     List<string> result = new List<string>();
52.     try
53.     {
54.         while (true)
55.         {
56.             string res = @this.SubstringEx(from, until, includeFrom, includeUntil, comparison);
57.  
58.             if (!skipEmptyResults || !string.IsNullOrEmpty(res)) // Skip empty result sets
59.                 result.Add(res);
60.  
61.             res = (!includeFrom) ? from + res : res;
62.  
63.             // If from and until are the same, then we can end up with problems and only returning half the result set. This fixes that problem.
64.             if (from != until)
65.                 res = (!includeUntil) ? res + until : res;
66.  
67.             @this = @this.Replace(res, string.Empty);
68.         }
69.     }
70.     catch { }
71.  
72.     return result;
73. }

End of Code Snippet