CODEWITHSUNDEEP
c#.netlinqlistcontains
Dimitris Iliadis
Dimitris Iliadis

Reputation: 2397

Check if list contains element that contains a string and get that element

While searching for an answer to this question, I've run into similar ones utilizing LINQ but I haven't been able to fully understand them (and thus, implement them), as I'm not familiarized with it. What I would like to, basically, is this:

  1. Check if any element of a list contains a specific string.
  2. If it does, get that element.

I honestly don't know how I would go about doing that. What I can come up with is this (not working, of course):

if (myList.Contains(myString))
    string element = myList.ElementAt(myList.IndexOf(myString));

I know WHY it does not work:

Still, I have no clue how to solve this problem, but I figure I'll have to use LINQ as suggested in similar questions to mine. That being said, if that's the case here, I'd like for the answerer to explain to me the use of LINQ in their example (as I said, I haven't bothered with it in my time with C#). Thank you in advance guys (and gals?).

EDIT: I have come up with a solution; just loop through the list, check if current element contains the string and then set a string equal to the current element. I'm wondering, though, is there a more efficient way than this?

string myString = "bla";
string element = "";

for (int i = 0; i < myList.Count; i++)
{
    if (myList[i].Contains(myString))
        element = myList[i];
}

Upvotes: 206

Views: 908653

Answers (13)

userda
userda

Reputation: 625

The basic answer is: you need to iterate through loop and check any element contains the specified string. So, let's say the code is:

foreach(string item in myList)
{
    if(item.Contains(myString))
       return item;
}

The equivalent, but terse, code is:

mylist.Where(x => x.Contains(myString)).FirstOrDefault();

Here, x is a parameter that acts like item in the above code.

Upvotes: 43

Abhay.Patil
Abhay.Patil

Reputation: 743

You can check the list is empty or not in multiple ways.

1)Check list is null and then check count is greater than zero like below:-

if(myList!=null && myList.Count>0)
{
    //List has more than one record.
}

2)Check list null and count greater than zero using linq query like below:-

if(myList!=null && myList.Count>0)
{
    //List has more than one record.
}

Upvotes: -2

deleb
deleb

Reputation: 604

It is possible to combine Any, Where, First and FirstOrDefault; or just place the predicate in any of those methods depending on what is needed.

You should probably avoid using First unless you want to have an exception thrown when no match is found. FirstOrDefault is usually the better option as long as you know it will return the type's default if no match is found (string's default is null, int is 0, bool is false, etc).

using System.Collections.Generic;
using System.Linq;


bool exists;
string firstMatch;
IEnumerable<string> matchingList;

var myList = new List<string>() { "foo", "bar", "foobar" };

exists = myList.Any(x => x.Contains("o"));
// exists => true

firstMatch = myList.FirstOrDefault(x => x.Contains("o"));
firstMatch = myList.First(x => x.Contains("o"));
// firstMatch => "foo"

firstMatch = myList.First(x => x.Contains("dark side"));
// throws exception because no element contains "dark side"

firstMatch = myList.FirstOrDefault(x => x.Contains("dark side"));
// firstMatch => null

matchingList = myList.Where(x => x.Contains("o")); 
// matchingList => { "foo", "foobar" }

Test this code @ https://rextester.com/TXDL57489

Upvotes: 1

Goku
Goku

Reputation: 207

You should be able to use something like this, it has worked okay for me:

var valuesToMatch = yourList.Where(stringCheck => stringCheck.Contains(myString));

or something like this, if you need to look where it doesn't match.

 var valuesToMatch = yourList.Where(stringCheck => !stringCheck.Contains(myString));

Upvotes: 2

Pawel Czapski
Pawel Czapski

Reputation: 1864

I have not seen bool option in other answers so I hope below code will help someone.

Just use Any()

string myString = "test";
bool exists = myList
             .Where(w => w.COLUMN_TO_CHECK.Contains(myString)).Any();

Upvotes: 0

Ali
Ali

Reputation: 1210

Many good answers here, but I use a simple one using Exists, as below:

foreach (var setting in FullList)
{
    if(cleanList.Exists(x => x.ProcedureName == setting.ProcedureName)) 
       setting.IsActive = true; // do you business logic here 
    else
       setting.IsActive = false;
    updateList.Add(setting);
}

Upvotes: 3

Alessandro D&#39;Andria
Alessandro D&#39;Andria

Reputation: 8878

If you want a list of strings containing your string:

var newList = myList.Where(x => x.Contains(myString)).ToList();

Another option is to use Linq FirstOrDefault

var element = myList.Where(x => x.Contains(myString)).FirstOrDefault();

Keep in mind that Contains method is case sensitive.

Upvotes: 7

devavx
devavx

Reputation: 1045

To keep it simple use this;

foreach(string item in myList)//Iterate through each item.
{
 if(item.Contains("Search Term")//True if the item contains search pattern.
 {
   return item;//Return the matched item.
 }
}

Alternatively,to do this with for loop,use this;

    for (int iterator = 0; iterator < myList.Count; iterator++)
    {
        if (myList[iterator].Contains("String Pattern"))
        {
            return myList[iterator];
        }
    }

Upvotes: 1

Nithin Nayagam
Nithin Nayagam

Reputation: 458

you can use

var match=myList.Where(item=>item.Contains("Required String"));
foreach(var i in match)
{
//do something with the matched items
}

LINQ provides you with capabilities to "query" any collection of data. You can use syntax like a database query (select, where, etc) on a collection (here the collection (list) of strings).

so you are doing like "get me items from the list Where it satisfies a given condition"

inside the Where you are using a "lambda expression"

to tell briefly lambda expression is something like (input parameter => return value)

so for a parameter "item", it returns "item.Contains("required string")" . So it returns true if the item contains the string and thereby it gets selected from the list since it satisfied the condition.

Upvotes: 1

p.s.w.g
p.s.w.g

Reputation: 149058

You could use Linq's FirstOrDefault extension method:

string element = myList.FirstOrDefault(s => s.Contains(myString));

This will return the fist element that contains the substring myString, or null if no such element is found.

If all you need is the index, use the List<T> class's FindIndex method:

int index = myList.FindIndex(s => s.Contains(myString));

This will return the the index of fist element that contains the substring myString, or -1 if no such element is found.

Upvotes: 3

McKay
McKay

Reputation: 12624

for (int i = 0; i < myList.Length; i++)
{
    if (myList[i].Contains(myString)) // (you use the word "contains". either equals or indexof might be appropriate)
    {
        return i;
    }
}

Old fashion loops are almost always the fastest.

Upvotes: 10

Dave Bish
Dave Bish

Reputation: 19646

You should be able to use Linq here:

var matchingvalues = myList
    .Where(stringToCheck => stringToCheck.Contains(myString));

If you simply wish to return the first matching item:

var match = myList
    .FirstOrDefault(stringToCheck => stringToCheck.Contains(myString));

if(match != null)
    //Do stuff

Upvotes: 272

Chris
Chris

Reputation: 1642

string result = myList.FirstOrDefault(x => x == myString)
if(result != null)
{
  //found
}

Upvotes: 15

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