Find an Item in a List by Linq

Find an item in a list by LINQ

If you want the index of the element, this will do it:

int index = list.Select((item, i) => new { Item = item, Index = i })
                .First(x => x.Item == search).Index;

// or
var tagged = list.Select((item, i) => new { Item = item, Index = i });
int index = (from pair in tagged
            where pair.Item == search
            select pair.Index).First();

You can't get rid of the lambda in the first pass.

Note that this will throw if the item doesn't exist. This solves the problem by resorting to nullable ints:

var tagged = list.Select((item, i) => new { Item = item, Index = (int?)i });
int? index = (from pair in tagged
            where pair.Item == search
            select pair.Index).FirstOrDefault();

If you want the item:

// Throws if not found
var item = list.First(item => item == search);
// or
var item = (from item in list
            where item == search
            select item).First();

// Null if not found
var item = list.FirstOrDefault(item => item == search);
// or
var item = (from item in list
            where item == search
            select item).FirstOrDefault();

If you want to count the number of items that match:

int count = list.Count(item => item == search);
// or
int count = (from item in list
            where item == search
            select item).Count();

If you want all the items that match:

var items = list.Where(item => item == search);
// or
var items = from item in list
            where item == search
            select item;

And don't forget to check the list for null in any of these cases.

Or use (list ?? Enumerable.Empty<string>()) instead of list.

How can I find object in List with Linq?

If you are trying to find an object in collectionMyObject which has item with id 2, then this should work:

MyObject myObject = collectionMyObject.FirstOrDefault(o => o.Items != null && o.Items.Any(io => io.Id == 2));

And if you are try to find an inner item with id 2, then this query with SelectMany might be helpful:

MyObject myObject1 = collectionMyObject.Where(o => o.Items != null).SelectMany(o => o.Items).FirstOrDefault(io => io.Id == 2);

linq - find item in list within multiple lists

Couldn't get it working with linq, but works with query syntax.

var leagueMatch = (from teamLeague in community.TeamLeagues
                from season in teamLeague.Seasons
                from division in season.Divisions
                from match in division.Matches.Where(x => x.Id == "1234")
                select match).FirstOrDefault();

LINQ query to find items in a list containing substring elements from a second list

We can use EndsWith() with Path.GetFileNameWithoutExtension(), as strings in the secondList are not entire file names.

var result = firstList
    .Where(path => secondList.Any(fileName => Path.GetFileNameWithoutExtension(path).EndsWith(fileName)));

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C# Linq Find value inside list of objects inside a list of objects

You should replace the Where method with Any mostly, because Where returns filtered sequence, when Any determines whether any element of a sequence satisfies a condition

var result = listProducts.Any(product =>
    product.title == "ERDSIC" && product.listProperties.Any(property =>
        property.title == "size" && property.listValues.Any(v => v.val == 1001)));

However, it's better to wrap this code into method, like extension one, and call with different arguments

public static class Ext
{
    public static bool HasTitleAndSize(this IEnumerable<Product> products, string title, int size)
    {
        return products.Any(product =>
            product.title == title && product.listProperties.Any(property =>
                property.title == "size" && property.listValues.Any(v => v.val == size)));
    }
}

And call in the following way

var result = listProducts.HasTitleAndSize("ERDSIC", 1001); //returns true
result = listProducts.HasTitleAndSize("ERDCON", 1001); //returns false

Linq select objects in list where exists IN (A,B,C)

Your status-codes are also a collection, so use Contains:

var allowedStatus = new[]{ "A", "B", "C" };
var filteredOrders = orders.Order.Where(o => allowedStatus.Contains(o.StatusCode));

or in query syntax:

var filteredOrders = from order in orders.Order
                     where allowedStatus.Contains(order.StatusCode)
                     select order;

LINQ query to find if items in a list are contained in another list

var test2NotInTest1 = test2.Where(t2 => test1.Count(t1 => t2.Contains(t1))==0);

Faster version as per Tim's suggestion:

var test2NotInTest1 = test2.Where(t2 => !test1.Any(t1 => t2.Contains(t1)));

Using LINQ to get a list of items where the item contains a part of an item from another list

var filteredList = models
    .Where(x => filterer.Any(y => x.Contains(y))
    .ToList();

Distinct serves no purpose here, as the Where call doesn't introduce duplicates (unless of course models has duplicate values, and you want to remove those duplicates).

Use LINQ to get items in one List , that are in another List

var result = peopleList2.Where(p => peopleList1.Any(p2 => p2.ID == p.ID));

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