How do I use LINQ Contains(string[]) instead of Contains(string)

Question

I got one big question.

I got a linq query to put it simply looks like this:

from xx in table
where xx.uid.ToString().Contains(string[])
select xx

The values of the string[] array would be numbers like (1,45,20,10,etc...)

the Default for .Contains is .Contains(string).

I need it to do this instead: .Contains(string[])...

EDIT : One user suggested writing an extension class for string[]. I would like to learn how, but any one willing to point me in the right direction?

EDIT : The uid would also be a number. That's why it is converted to a string.

Help anyone?

Betony

You need to clarify would a uid might look like, and what would be considered a match. – Grower

An example would be nice. It sounds to me like the question is asking for a UID like: CA1FAB689C33 and the array like: { "42", "2259", "CA" } – Epistrophe

Opposite makes more sense: string[].Contains( xx.uid ) – Hey

Answer 1

spoulson has it nearly right, but you need to create a List<string> from string[] first. Actually a List<int> would be better if uid is also int. List<T> supports Contains(). Doing uid.ToString().Contains(string[]) would imply that the uid as a string contains all of the values of the array as a substring??? Even if you did write the extension method the sense of it would be wrong.

[EDIT]

Unless you changed it around and wrote it for string[] as Mitch Wheat demonstrates, then you'd just be able to skip the conversion step.

[ENDEDIT]

Here is what you want, if you don't do the extension method (unless you already have the collection of potential uids as ints -- then just use List<int>() instead). This uses the chained method syntax, which I think is cleaner, and does the conversion to int to ensure that the query can be used with more providers.

var uids = arrayofuids.Select(id => int.Parse(id)).ToList();

var selected = table.Where(t => uids.Contains(t.uid));

Weakminded

Thank you. It was the right answer... One more thought? Lets say the arrayuids is also a linq query. Any way you could get both statements down to just one query from the database? – Betony

According to MSDN, string[] implements IEnumerable<T>, which has a Contains method. Therefore, it's not necessary to convert the array to an IList<T>. msdn.microsoft.com/en-us/library/19e6zeyy.aspx – Jacaranda

The last .ToString() throws errors for me. Specifically, LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression.... After removing it, the lambda worked for me. – Aucoin

I love this, it's so easy that i never remember it. – Charismatic

@SamStange - one problem with LINQ is that there are so many variants and the abstraction is "leaky", you sometimes need to know which variant you are using in order to construct the query properly. As written this would work for LINQ to objects (and may be LINQ to SQL). For EF, you'd do it the other way around and construct the collection in memory as List<int> instead and skip the ToString call. – Weakminded

HashSet would be even faster – Ignacia

@Blam unless it's a query that's being converted to SQL, which I think was the context at the time. – Weakminded

Answer 2

If you are truly looking to replicate Contains, but for an array, here is an extension method and sample code for usage:

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

namespace ContainsAnyThingy
{
    class Program
    {
        static void Main(string[] args)
        {
            string testValue = "123345789";

            //will print true
            Console.WriteLine(testValue.ContainsAny("123", "987", "554")); 

            //but so will this also print true
            Console.WriteLine(testValue.ContainsAny("1", "987", "554"));
            Console.ReadKey();

        }
    }

    public static class StringExtensions
    {
        public static bool ContainsAny(this string str, params string[] values)
        {
            if (!string.IsNullOrEmpty(str) || values.Length > 0)
            {
                foreach (string value in values)
                {
                    if(str.Contains(value))
                        return true;
                }
            }

            return false;
        }
    }
}

Wong

+1 @Jason, you should totally submit this to ExtensionMethod.net Thanks for the great code, it solved my problem today! – Volume

I think you meant !string.IsNullOrEmpty(str) && values.Length > 0 – Nickey

You are right. I changed it, though it doesn't have a functional impact. I use a function like this at work. I will have to check it! – Wong

@JasonJackson I realize this is old(ish), but (as Greg mentioned) don't you want an "and also" rather than an "or else" in that conditional? – Ryder

@TiesonT. Both the "or else" and "and also" conditionals would end up with the same result returned by the function; if the !string.IsNullOrEmpty(str) check passed, causing the values.Length > 0 condition to be ignored, but the length of Values was 0, then it would go to the foreach and then break immediately because there are no entries in the array, going directly to the return false. – Culinarian

@GreenCat77 That's true, but why even go into the loop if there are no items in value? – Ryder

Finally an example to show how to search for array strings within another string. – Gunderson

Greg Bogumil is right, it should be && not || in the if statement. Otherwise, the first check is pointless if values is not empty. – Kisner

Answer 3

Try the following.

string input = "someString";
string[] toSearchFor = GetSearchStrings();
var containsAll = toSearchFor.All(x => input.Contains(x));

Upton

I really wish people would leave a comment when they mark you down. Especially since the answer I provided is 100% correct. – Upton

It wasn't me, but doesn't All() return simply a bool indicating where all items match the condition? And initializing toSearchFor to null guarantess a NullReferenceException. – Parrakeet

I editted the null issue to be what I intended to type. Yes on All. This effectively ensures that all strings in toSearchFor are contained within the input string. – Upton

I don't see how this answers the question at all. Did the question morph on you? – Weakminded

Answer 4

LINQ in .NET 4.0 has another option for you; the .Any() method;

string[] values = new[] { "1", "2", "3" };
string data = "some string 1";
bool containsAny = values.Any(data.Contains);

Brisance

Great answer, expressions with Any() and All() methods are so simple :) I can use t => words.All(w => t.Title.Contains(w)). – Quantum

Answer 5

Or if you already have the data in a list and prefer the other Linq format :)

List<string> uids = new List<string>(){"1", "45", "20", "10"};
List<user> table = GetDataFromSomewhere();

List<user> newTable = table.Where(xx => uids.Contains(xx.uid)).ToList();

Oswald

Answer 6

How about:

from xx in table
where stringarray.Contains(xx.uid.ToString())
select xx

Jacaranda

NotSupportedException: Comparison operators not supported for type 'System.String[]' Thanks but try again? – Betony

+1, if this is actually what they want. It's not very clear from the question. – Parrakeet

Answer 7

This is an example of one way of writing an extension method (note: I wouldn't use this for very large arrays; another data structure would be more appropriate...):

namespace StringExtensionMethods
{
    public static class StringExtension
    {
        public static bool Contains(this string[] stringarray, string pat)
        {
            bool result = false;

            foreach (string s in stringarray)
            {
                if (s == pat)
                {
                    result = true;
                    break;
                }
            }

            return result;
        }
    }
}

Shon

that would be identical to public static bool Contains(this string[] stringarray, string pat) { return Array.IndexOf(stringarray, pat) != -1; } – Grower

string[] implements IEnumerable<string>, so it already has a Contains(string) extension method. Why are we reimplementing this? – Parrakeet

Answer 8

This is a late answer, but I believe it is still useful.
I have created the NinjaNye.SearchExtension nuget package that can help solve this very problem.:

string[] terms = new[]{"search", "term", "collection"};
var result = context.Table.Search(terms, x => x.Name);

You could also search multiple string properties

var result = context.Table.Search(terms, x => x.Name, p.Description);

Or perform a RankedSearch which returns IQueryable<IRanked<T>> which simply includes a property which shows how many times the search terms appeared:

//Perform search and rank results by the most hits
var result = context.Table.RankedSearch(terms, x => x.Name, x.Description)
                     .OrderByDescending(r = r.Hits);

There is a more extensive guide on the projects GitHub page: https://github.com/ninjanye/SearchExtensions

Hope this helps future visitors

Sowell

Yes, it's been specifically built to target Entity Framework – Sowell

Can I use this with .Where() method as well? – Isaacisaacs

Yeah, it works on IQueryable and IEnumerable - just be awayre that if you chain it off an IEnumerable, it will be running in memeory rather than building a query and sending it down to the source – Sowell

Answer 9

Linq extension method. Will work with any IEnumerable object:

    public static bool ContainsAny<T>(this IEnumerable<T> Collection, IEnumerable<T> Values)
    {
        return Collection.Any(x=> Values.Contains(x));
    }

Usage:

string[] Array1 = {"1", "2"};
string[] Array2 = {"2", "4"};

bool Array2ItemsInArray1 = List1.ContainsAny(List2);

Peti

Answer 10

I believe you could also do something like this.

from xx in table
where (from yy in string[] 
       select yy).Contains(xx.uid.ToString())
select xx

Wilder

Same as "where stringArray.Contains(xx.uid.ToString())", no need to wrap it around in a query – Parrakeet

Answer 11

You should write it the other way around, checking your priviliged user id list contains the id on that row of table:

string[] search = new string[] { "2", "3" };
var result = from x in xx where search.Contains(x.uid.ToString()) select x;

LINQ behaves quite bright here and converts it to a good SQL statement:

sp_executesql N'SELECT [t0].[uid]
FROM [dbo].[xx] AS [t0]
WHERE (CONVERT(NVarChar,[t0].[uid]))
IN (@p0, @p1)',N'@p0 nvarchar(1),
@p1 nvarchar(1)',@p0=N'2',@p1=N'3'

which basicly embeds the contents of the 'search' array into the sql query, and does the filtering with 'IN' keyword in SQL.

Predate

This works fine as long as you don't have over 2100 parameters. – Spiegeleisen

Answer 12

So am I assuming correctly that uid is a Unique Identifier (Guid)? Is this just an example of a possible scenario or are you really trying to find a guid that matches an array of strings?

If this is true you may want to really rethink this whole approach, this seems like a really bad idea. You should probably be trying to match a Guid to a Guid

Guid id = new Guid(uid);
var query = from xx in table
            where xx.uid == id
            select xx;

I honestly can't imagine a scenario where matching a string array using "contains" to the contents of a Guid would be a good idea. For one thing, Contains() will not guarantee the order of numbers in the Guid so you could potentially match multiple items. Not to mention comparing guids this way would be way slower than just doing it directly.

Entirely

Answer 13

I managed to find a solution, but not a great one as it requires using AsEnumerable() which is going to return all results from the DB, fortunately I only have 1k records in the table so it isn't really noticable, but here goes.

var users = from u in (from u in ctx.Users
                       where u.Mod_Status != "D"
                       select u).AsEnumerable()
            where ar.All(n => u.FullName.IndexOf(n,
                        StringComparison.InvariantCultureIgnoreCase) >= 0)
            select u;

---

My original post follows:

How do you do the reverse? I want to do something like the following in entity framework.

string[] search = new string[] { "John", "Doe" };
var users = from u in ctx.Users
            from s in search
           where u.FullName.Contains(s)
          select u;

What I want is to find all users where their FullName contains all of the elements in `search'. I've tried a number of different ways, all of which haven't been working for me.

I've also tried

var users = from u in ctx.Users select u;
foreach (string s in search) {
    users = users.Where(u => u.FullName.Contains(s));
}

This version only finds those that contain the last element in the search array.

Waistcoat

Answer 14

The best solution I found was to go ahead and create a Table-Valued Function in SQL that produces the results, such as ::

CREATE function [dbo].[getMatches](@textStr nvarchar(50)) returns @MatchTbl table(
Fullname nvarchar(50) null,
ID nvarchar(50) null
)
as begin
declare @SearchStr nvarchar(50);
set @SearchStr = '%' + @textStr + '%';
insert into @MatchTbl 
select (LName + ', ' + FName + ' ' + MName) AS FullName, ID = ID from employees where LName like @SearchStr;
return;
end

GO

select * from dbo.getMatches('j')

Then, you simply drag the function into your LINQ.dbml designer and call it like you do your other objects. The LINQ even knows the columns of your stored function. I call it out like this ::

Dim db As New NobleLINQ
Dim LNameSearch As String = txt_searchLName.Text
Dim hlink As HyperLink

For Each ee In db.getMatches(LNameSearch)
   hlink = New HyperLink With {.Text = ee.Fullname & "<br />", .NavigateUrl = "?ID=" & ee.ID}
   pnl_results.Controls.Add(hlink)
Next

Incredibly simple and really utlizes the power of SQL and LINQ in the application...and you can, of course, generate any table valued function you want for the same effects!

Cardigan

Answer 15

I believe that what you really want to do is: let's imagine a scenario you have two database and they have a table of products in common And you want to select products from the table "A" that id has in common with the "B"

using the method contains would be too complicated to do this what we are doing is an intersection, and there is a method called intersection for that

an example from msdn: http://msdn.microsoft.com/en-us/vcsharp/aa336761.aspx#intersect1

int [] numbers = (0, 2, 4, 5, 6, 8, 9); int [] numbersB = (1, 3, 5, 7, 8); var = commonNumbers numbersA.Intersect (numbersB);

I think what you need is easily solved with intersection

Holmen

Answer 16

from xx in table
where xx.uid.Split(',').Contains(string value )
select xx

Tropical

Answer 17

Check this extension method:

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

namespace ContainsAnyProgram
{
    class Program
    {
        static void Main(string[] args)
        {
            const string iphoneAgent = "Mozilla/5.0 (iPhone; CPU iPhone OS 5_0 like...";

            var majorAgents = new[] { "iPhone", "Android", "iPad" };
            var minorAgents = new[] { "Blackberry", "Windows Phone" };

            // true
            Console.WriteLine(iphoneAgent.ContainsAny(majorAgents));

            // false
            Console.WriteLine(iphoneAgent.ContainsAny(minorAgents));
            Console.ReadKey();
        }
    }

    public static class StringExtensions
    {
        /// <summary>
        /// Replicates Contains but for an array
        /// </summary>
        /// <param name="str">The string.</param>
        /// <param name="values">The values.</param>
        /// <returns></returns>
        public static bool ContainsAny(this string str, params string[] values)
        {
            if (!string.IsNullOrEmpty(str) && values.Length > 0)
                return values.Any(str.Contains);

            return false;
        }
    }
}

Lindeberg

Answer 18

Try:

var stringInput = "test";
var listOfNames = GetNames();
var result = from names in listOfNames where names.firstName.Trim().ToLower().Contains(stringInput.Trim().ToLower());
select names;

Bushy

While this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value. – Shererd

Answer 19

var SelecetdSteps = Context.FFTrakingSubCriticalSteps
             .Where(x => x.MeetingId == meetid)
             .Select(x =>    
         x.StepID  
             );

        var crtiticalsteps = Context.MT_CriticalSteps.Where(x =>x.cropid==FFT.Cropid).Select(x=>new
        {
            StepID= x.crsid,
            x.Name,
            Checked=false

        });


        var quer = from ax in crtiticalsteps
                   where (!SelecetdSteps.Contains(ax.StepID))
                   select ax;

Gidgetgie

Answer 20

        string texto = "CALCA 40";
        string[] descpart = texto.Split(' ');

        var lst = (from item in db.InvItemsMaster
                   where descpart.All(val => item.itm_desc.Contains(val))
                   select item
                    ).ToList();
        Console.WriteLine("ITM".PadRight(10) + "DESC".PadRight(50)+"EAN".PadRight(14));
        foreach(var i in lst)
        {
           

            Console.Write(i.itm_id.ToString().PadRight(10));
            Console.Write(i.itm_desc.ToString().PadRight(50));
            Console.WriteLine(i.itm_ean.ToString().PadRight(14));


        }

        Console.ReadKey();

Ronni

We,come to SO. Please don't give "code only" answers. Could you add some explanation how this solves the problem and is not already covered by the other 21 answers? – Vaughan

Answer 21

string[] stringArray = {1,45,20,10};
from xx in table 
where stringArray.Contains(xx.uid.ToString()) 
select xx

Riven

Answer 22

Dim stringArray() = {"Pink Floyd", "AC/DC"}
Dim inSQL = From alb In albums Where stringArray.Contains(alb.Field(Of String)("Artiste").ToString())
Select New With
  {
     .Album = alb.Field(Of String)("Album"),
     .Annee = StrReverse(alb.Field(Of Integer)("Annee").ToString()) 
  }

Natatorium