Search for strings in a list that contain specified words

Question

Hi everyone

I use extension method Where to filter a list

IEnumerable<string> result = myList<string>.Where(s=>s.Contains(textBox1.Text));

In the myList i have some strings i.e

"a b c d", "c d e f" ,"a b e f", "d e f g"

This works fine but requires me to provide words in specified order in textBox.  When i provide string " c d" i get "a b c d" and "c d e f"

but i'd like to  get the same result when i provide "d c" and in addition string "d e f g" because 'd' is in it.

What's the best way to do that?

Answer 1

var result = myList.Where(str => str.Any( character => textBox1.Text.Contains(character) );

If you are going to enter more than just a few characters in the list you should consider loading the textbox text into a HashSet, but for just a few characters it will be just fine as it is.

Answer 2

I was just fiddling with this. My answer was just a tad more lengthy. Assume the variable "text" is your textBox1.Text

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            String[] test = { "abcd", "cdef", "abef", "defg" };
            String text = "e";
            String[] result = test.Where(s =>
                {
                    Boolean isInThere = true;
                    Char[] textArray = text.ToCharArray();
                    foreach (Char c in textArray)
                    {
                        if (!s.Contains(c))
                            isInThere = false;
                    }
                    return isInThere;
                }).ToArray();
        }
    }
}

---

John Grove, Senior Software Engineer http://www.digitizedschematic.com/

Answer 3

@John, you could add a break in the 'if' statement of your 'for' loop.

That's one of the advantages of using 'Any', you get the built in short circuiting.

The converting to a char array is also not needed; string implements IEnumerable<char> all on it's own.

Answer 4

Yea, your example was much better. I was just trying to do it trying something different.

---

John Grove, Senior Software Engineer http://www.digitizedschematic.com/

Answer 5

Could you tell me how to use HashSet in this case, because i might need to search longer strings?

What if the List contains long strings (sentences) and i want to find all sentences that contain words written in TextBox?

ie

List<string> sentences = new List<string>();
sentences.Add("This is a long sentence.");
sentences.Add("This is another long sentence.");
sentences.Add(...    //adding more sentences

How to search  that list(the words in the TextBox are in custom order)?

Answer 6

var searchWords = new HashSet<string>(textbox1.Text.Split(' '));
var results = sentances.Where(sentance => sentance.Split(' ')
    .Any(word => searchWords.Contains(word)));

Note that what you're doing won't scale particularly well, so if you have a lot of strings that you're searching this could get fairly slow.

Answer 7

Find the items of myList for which there is at least 1 word among those from the textbox:

IEnumerable<string> result = myList.Where(s => s.Split().Intersect(textBox1.Text.Split()).Any());

Answer 8

var result = myList.Where(str => str.Any( character => textBox1.Text.Contains(character) );

(str => str.Any(...)  ---> Any is not accessible after definisng a "str" parameter in VS 2008 and lower versions.

At least I dont have it in the intellisence.

---

Mitja

Answer 9

(str => str.Any(...)  ---> Any is not accessible after definisng a "str" parameter in VS 2008 and lower versions.

At least I dont have it in the intellisence.

It compiles just fine in .NET 3.5 with VS 2010.

Answer 10

Find the items of myList for which there is at least 1 word among those from the textbox:

IEnumerable<string> result = myList.Where(s => s.Split().Intersect(textBox1.Text.Split()).Any());

First off, you're splitting the textbox text with every single iteration.  You only need to split it once.  With this solution you're also adding its contents to a HashSet on every single string in the list, rather than just doing it once at the start.  

Answer 11

Another question.

IEnumerable<string> result = myList.Where(s => s.Split().Intersect(textBox1.Text.Split()).Any());

This finds all strings contain at least one word from the TextBox but what when we want to find strings contain all words typed in TextBox

Answer 12

First off, you're splitting the textbox text with every single iteration.  You only need to split it once. 

Right. It's better to store the result of the split into a variable.

Answer 13

Find each item of the list which contains all the words to find.

string[] wordsToFind = textBox1Text.Split();
IEnumerable<string> result = myList.Where(s => wordsToFind.All(s.Split().Contains));

Answer 14

what does "Contains" do in this case?
  Does it check if splitted string contains an element from wordsToFind?

Answer 15

My previous sample does the same thing as this one:

string[] wordsToFind = textBox1Text.Split();
IEnumerable<string> result = myList.Where(s => wordsToFind.All(w => s.Split().Contains(w)));

Every time you want a delegate and write a lambda of the form x => foo(x) , you could simply use the method foo directly.