c# regular-expression search format the search prase if boolean and or not prese

The following allows for NOT, AND and OR - in that order of precedence - and assumes the search string is well formed. If you want to allow for more operators than this, then you'll probably need to write a recursive-descent parser which isn't an easy task:

using System;

using System.Collections.Generic;

using System.Text.RegularExpressions;

class Program

{

static void Main()

{

string[] records = new string[6];

records[0] = "Sachin, Lara and Ponting are great cricket players";

records[1] = "Sachin and Lara are great cricket players";

records[2] = "Sachin is a great cricket player";

records[3] = "Ponting plays for Australia";

records[4] = "Lara used to play for West Indies";

records[5] = "Sachin plays for India and " + records[4];

string search = "sachin and not lara or ponting";

string[] found = Find(records, search);

if (found.Length == 0)

{

Console.WriteLine("No records match the search criteria");

}

else

{

Console.WriteLine("The following {0} record(s) match the search criteria:\n", found.Length);

foreach(string record in found) Console.WriteLine(record);

}

Console.ReadKey();

}

static string[] Find(string[] records, string search)

{

List matches = new List();

search = search.ToLower().Replace("not ", "~").Replace(" and ", "&");

string[] words = Regex.Split(search.ToLower(), @"\s+or\s+");

for(int i = 0; i < records.Length; i++)

{

string record = records[i].Trim().ToLower();

for(int j = 0; j < words.Length; j++)

{

if (FindWord(record, words[j]))

{

matches.Add(records[i]);

break;

}

return matches.ToArray();

}

static bool FindWord(string record, string word)

{

string[] subwords = word.Split('&');

foreach(string subword in subwords)

{

if(subword[0] != '~')

{

if (!Regex.IsMatch(record, subword)) return false;

}

else

{

if (Regex.IsMatch(record, subword.Substring(1))) return false;

}

return true;

}

The output should be:

Sachin, Lara and Ponting are great cricket players

Sachin is a great cricket player

Ponting plays for Australia

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes15y ago
The following allows for NOT, AND and OR - in that order of precedence - and assumes the search string is well formed. If you want to allow for more operators than this, then you'll probably need to write a recursive-descent parser which isn't an easy task:

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

class Program
{
   static void Main()
   {
   string[] records = new string[6];
   records[0] = "Sachin, Lara and Ponting are great cricket players";
   records[1] = "Sachin and Lara are great cricket players";
   records[2] = "Sachin is a great cricket player";
   records[3] = "Ponting plays for Australia";
   records[4] = "Lara used to play for West Indies";
   records[5] = "Sachin plays for India and " + records[4];
   string search = "sachin and not lara or ponting";
   string[] found = Find(records, search);

   if (found.Length == 0)
   {
   Console.WriteLine("No records match the search criteria");
   }
   else
   {
   Console.WriteLine("The following {0} record(s) match the search criteria:\n", found.Length);
   foreach(string record in found) Console.WriteLine(record);
   }

   Console.ReadKey();
   }

   static string[] Find(string[] records, string search)
   {
   List matches = new List();
   search = search.ToLower().Replace("not ", "~").Replace(" and ", "&");
   string[] words = Regex.Split(search.ToLower(), @"\s+or\s+");

   for(int i = 0; i < records.Length; i++)
   {
   string record = records[i].Trim().ToLower();
   for(int j = 0; j < words.Length; j++)
   {
   if (FindWord(record, words[j]))
   {
   matches.Add(records[i]);
   break;
   }
   }
   }

   return matches.ToArray();
   }

   static bool FindWord(string record, string word)
   {
   string[] subwords = word.Split('&');

   foreach(string subword in subwords)
   {
   if(subword[0] != '~')
   {
   if (!Regex.IsMatch(record, subword)) return false;
   }
   else
   {
   if (Regex.IsMatch(record, subword.Substring(1))) return false;
   }
   }
   return true;
   }
}

The output should be:

Sachin, Lara and Ponting are great cricket players
Sachin is a great cricket player
Ponting plays for Australia
vas may15y ago
its not a boolean search..
Karthikeyan Anbarasan15y ago
Hope this link will be useful http://www.codeproject.com/KB/aspnet/m1.aspx