Tutorial by Examples

Returns a subset of items which the specified predicate is true for them. List<string> trees = new List<string>{ "Oak", "Birch", "Beech", "Elm", "Hazel", "Maple" }; Method syntax // Select all trees with name of length 3 v...

Select allows you to apply a transformation to every element in any data structure implementing IEnumerable. Getting the first character of each string in the following list: List<String> trees = new List<String>{ "Oak", "Birch", "Beech", "Elm", ...

Many LINQ functions both operate on an IEnumerable<TSource> and also return an IEnumerable<TResult>. The type parameters TSource and TResult may or may not refer to the same type, depending on the method in question and any functions passed to it. A few examples of this are public stat...

The Range and Repeat static methods on Enumerable can be used to generate simple sequences. Range Enumerable.Range() generates a sequence of integers given a starting value and a count. // Generate a collection containing the numbers 1-100 ([1, 2, 3, ..., 98, 99, 100]) var range = Enumerable.Ran...

The Skip method returns a collection excluding a number of items from the beginning of the source collection. The number of items excluded is the number given as an argument. If there are less items in the collection than specified in the argument then an empty collection is returned. The Take meth...

All six methods return a single value of the sequence type, and can be called with or without a predicate. Depending on the number of elements that match the predicate or, if no predicate is supplied, the number of elements in the source sequence, they behave as follows: First() Returns the fir...

The Except method returns the set of items which are contained in the first collection but are not contained in the second. The default IEqualityComparer is used to compare the items within the two sets. There is an overload which accepts an IEqualityComparer as an argument. Example: int[] first =...

var sequenceOfSequences = new [] { new [] { 1, 2, 3 }, new [] { 4, 5 }, new [] { 6 } }; var sequence = sequenceOfSequences.SelectMany(x => x); // returns { 1, 2, 3, 4, 5, 6 } Use SelectMany() if you have, or you are creating a sequence of sequences, but you want the result as one long sequen...

The SelectMany linq method 'flattens' an IEnumerable<IEnumerable<T>> into an IEnumerable<T>. All of the T elements within the IEnumerable instances contained in the source IEnumerable will be combined into a single IEnumerable. var words = new [] { "a,b,c", "d,e&quo...

All is used to check, if all elements of a collection match a condition or not. see also: .Any 1. Empty parameter All: is not allowed to be used with empty parameter. 2. Lambda expression as parameter All: Returns true if all elements of collection satisfies the lambda expression and false othe...

interface IFoo { } class Foo : IFoo { } class Bar : IFoo { } var item0 = new Foo(); var item1 = new Foo(); var item2 = new Bar(); var item3 = new Bar(); var collection = new IFoo[] { item0, item1, item2, item3 }; Using OfType var foos = collection.OfType<Foo>(); // result: IEnum...

Merges two collections to create a distinct collection using the default equality comparer int[] numbers1 = { 1, 2, 3 }; int[] numbers2 = { 2, 3, 4, 5 }; var allElement = numbers1.Union(numbers2); // AllElement now contains 1,2,3,4,5 Live Demo on .NET Fiddle

Joins are used to combine different lists or tables holding data via a common key. Like in SQL, the following kinds of Joins are supported in LINQ: Inner, Left, Right, Cross and Full Outer Joins. The following two lists are used in the examples below: var first = new List<string>(){ &quot...

Returns unique values from an IEnumerable. Uniqueness is determined using the default equality comparer. int[] array = { 1, 2, 3, 4, 2, 5, 3, 1, 2 }; var distinct = array.Distinct(); // distinct = { 1, 2, 3, 4, 5 } To compare a custom data type, we need to implement the IEquatable<T> i...

Lets assume we have some Film model: public class Film { public string Title { get; set; } public string Category { get; set; } public int Year { get; set; } } Group by Category property: foreach (var grp in films.GroupBy(f => f.Category)) { var groupCategory = grp.Key; ...

You can use the Enumerable class alongside Linq queries to convert for loops into Linq one liners. Select Example Opposed to doing this: var asciiCharacters = new List<char>(); for (var x = 0; x < 256; x++) { asciiCharacters.Add((char)x); } You can do this: var asciiCharacter...

string[] names= { "mark", "steve", "adam" }; Ascending: Query Syntax var sortedNames = from name in names orderby name select name; Method Syntax var sortedNames = names.OrderBy(name => name); sortedNames contains the names in following ord...

LINQ is largely beneficial for querying collections (or arrays). For example, given the following sample data: var classroom = new Classroom { new Student { Name = "Alice", Grade = 97, HasSnack = true }, new Student { Name = "Bob", Grade = 82, HasSnack = false }, ...

GroupBy is an easy way to sort a IEnumerable<T> collection of items into distinct groups. Simple Example In this first example, we end up with two groups, odd and even items. List<int> iList = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; var grouped = iList.GroupBy(x => x ...

Any is used to check if any element of a collection matches a condition or not. see also: .All, Any and FirstOrDefault: best practice 1. Empty parameter Any: Returns true if the collection has any elements and false if the collection is empty: var numbers = new List<int>(); bool result = ...