Solved

LINQ Query: Multiple "StartsWith"

Posted on 2011-03-15
5
1,718 Views
Last Modified: 2012-05-11
Briefly:
      string[] myarray = { "banana", "apple", "badminton","sansa stark" };
      string[] lookup = {"a", "ban"};
      string[] query = ???;

How do I use "lookup" as a "StartsWith" filter?  Query should return "apple" and "banana".  Both method-based and the verbose version would be greatly appreciated...
0
Comment
Question by:tknudsen-qec
  • 2
  • 2
5 Comments
 
LVL 53

Expert Comment

by:Dhaest
ID: 35138647
Below you can find an example with a list of strings (which is in my eyes a better solution)
public static class StringExtensions 
    { 
        public static bool StartsWithAny(this string s, IEnumerable<string> items) 
        { return items.Any(i => s.StartsWith(i)); 
        } 
    } 

   public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            List<string> myarray = new List<string>() { "banana", "apple", "badminton", "sansa stark" };
            List<string> lookup = new List<string>{"a", "ban"};
            var query = from x in myarray where x.StartsWithAny(lookup) select x;
            foreach (string x in query)
            {
                MessageBox.Show (x);
            }
        }

}

Open in new window

0
 
LVL 53

Expert Comment

by:Dhaest
ID: 35138660
Added a small example how you can easily transform your string[] into list<string> and use the same query
public static class StringExtensions 
    { 
        public static bool StartsWithAny(this string s, IEnumerable<string> items) 
        { return items.Any(i => s.StartsWith(i)); 
        } 
    } 


        private void Form1_Load(object sender, EventArgs e)
        {

            string[] myList = { "banana", "apple", "badminton","sansa stark" };
            string[] lookupList = {"a", "ban"};


            List<string> StringtoList = new List<string>(myList.Length);//AddRange is a method of List<T> objects that enables the conversion.//We just need to pass the reference to the array.            
            StringtoList.AddRange(myList);

            List<string> LookuptoList = new List<string>(lookupList.Length);//AddRange is a method of List<T> objects that enables the conversion.//We just need to pass the reference to the array.            
            LookuptoList.AddRange(lookupList);

            query = from x in myarray where x.StartsWithAny(lookup) select x;
}

}

Open in new window

0
 
LVL 75

Accepted Solution

by:
käµfm³d   👽 earned 500 total points
ID: 35138832
Here's my offering:
string[] queryResult = myarray.Where(item => lookup.Any(l => item.StartsWith(l))).ToArray();

Open in new window

0
 
LVL 3

Author Closing Comment

by:tknudsen-qec
ID: 35138967
kaufmed: works great and is clean.  Thanks kindly.

I couldn't get prior solution to work although at a glance I think it just needed a bit of cleaning up and a refresher on method extensions.
0
 
LVL 75

Expert Comment

by:käµfm³d 👽
ID: 35139211
NP. Glad to help  : )
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Extention Methods in C# 3.0 by Ivo Stoykov C# 3.0 offers extension methods. They allow extending existing classes without changing the class's source code or relying on inheritance. These are static methods invoked as instance method. This…
Introduction Hi all and welcome to my first article on Experts Exchange. A while ago, someone asked me if i could do some tutorials on object oriented programming. I decided to do them on C#. Now you may ask me, why's that? Well, one of the re…
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …
In a recent question (https://www.experts-exchange.com/questions/29004105/Run-AutoHotkey-script-directly-from-Notepad.html) here at Experts Exchange, a member asked how to run an AutoHotkey script (.AHK) directly from Notepad++ (aka NPP). This video…

856 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question