C# Lambda in List

Lambda expressions can be used with list operations to make them more concise and expressive. Here we have some common list operations and how to use lambda expressions with them:

Filtering with Where:

The "Where" method is used to filter a list based on a given condition. It takes a lambda expression as a parameter and returns a new list containing only the elements that meet the condition.

Example:

List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
List<int> evenNumbers = numbers.Where(x => x % 2 == 0).ToList();

The "Select" method in C# can be used to project each element of a list into a new form. It takes a lambda expression as a parameter and returns a new list with the projected elements.

Example:

List<string> names = new List<string> { "Alice", "Bob", "Charlie" };
List<int> nameLengths = names.Select(name => name.Length).ToList();

Using "Find" method we can search for an element in a list. It takes a lambda expression as a parameter and returns the first element that satisfies condition.

Example:

List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
int firstEvenNumber = numbers.Find(x => x % 2 == 0);

We can use "ForEach" method to perform an action on each element of a list. It takes a lambda expression as a parameter and executes the action for each element.

Example:

List<string> names = new List<string> { "Alice", "Bob", "Charlie" };
names.ForEach(name => Console.WriteLine(name));

The "Sort" method in C# can be used to sort a list based on a specified comparer. It takes a lambda expression as a parameter and sorts the list according to the provided comparison logic.

Example:

List<int> numbers = new List<int> { 5, 3, 1, 4, 2 };
numbers.Sort((x, y) => x.CompareTo(y));
						

Here are 26 code samples demonstrating various ways to use C# lists with lambda expressions:

1. Filter a list of integers for even numbers:

   List<int> evenNumbers = numbers.Where(x => x % 2 == 0).ToList();
   

2. Filter a list of strings for those containing a specific substring:

   List<string> filteredStrings = strings.Where(s => s.Contains("keyword")).ToList();
   

3. Count elements in a list that match a given condition:

   int count = numbers.Count(x => x > 10);
   

4. Check if any element in a list matches a given condition:

   bool hasNegative = numbers.Any(x => x < 0);
   

5. Check if all elements in a list match a given condition:

   bool allPositive = numbers.All(x => x >= 0);
   

6. Find the maximum element in a list:

   int max = numbers.Max();
   

7. Find the minimum element in a list:

   int min = numbers.Min();
   

8. Calculate the sum of all elements in a list:

   int sum = numbers.Sum();
   

9. Calculate the average of all elements in a list:

   double average = numbers.Average();
   

10. Concatenate two lists:

    List<int> concatenatedList = list1.Concat(list2).ToList();
    

11. Create a dictionary from a list:

    Dictionary<int, string> dict = list.ToDictionary(x => x.Key, x => x.Value);
    

12. Remove duplicates from a list:

    List<int> distinctNumbers = numbers.Distinct().ToList();
    

13. Reverse the order of elements in a list:

    List<int> reversedList = numbers.Reverse().ToList();
    

14. Group elements in a list by a key:

    var groups = people.GroupBy(p => p.Age);
    

15. Combine elements of two lists using a function:

    List<int> combinedList = list1.Zip(list2, (x, y) => x + y).ToList();
    

16. Take the first "n" elements from a list:

    List<int> firstNElements = numbers.Take(3).ToList();
    

17. Skip the first "n" elements of a list:

    List<int> remainingElements = numbers.Skip(3).ToList();
    

18. Partition a list into fixed-sized groups:

    List<List<int>> groups = numbers.Select((x, i) => new { Index = i, Value = x })
                                     .GroupBy(x => x.Index / 3)
                                     .Select(g => g.Select(x => x.Value).ToList())
                                     .ToList();
    

19. Find the index of the first element that matches a given condition:

    int index = numbers.FindIndex(x => x == 42);
    

20. Convert a list of strings to a single string:

    string result = string.Join(", ", strings);
    

21. Remove elements from a list that match a given condition:

    numbers.RemoveAll(x => x % 2 == 0);
    

22. Convert a list of objects to a list of their property values:

    List<string> names = people.Select(p => p.Name).ToList();
    

23. Sort a list of objects by a specific property:

    List<Person> sortedPeople = people.OrderBy(p => p.Age).ToList();
    

24. Sort a list of objects by multiple properties:

    List<Person> sortedPeople = people.OrderBy(p => p.Age).ThenBy(p => p.Name).ToList();
    

25. Create a list of objects from two lists with corresponding elements:

    List<Tuple<int, string>> pairedList = list1.Zip(list2, (x, y) => Tuple.Create(x, y)).ToList();
    

26. Flatten a list of lists into a single list:

    List<int> flattenedList = listOfLists.SelectMany(x => x).ToList();
    

Lambda expressions in C# offer a powerful and expressive way to work with lists, using lambda expressions in conjunction with various list operations, developers can write more concise and readable code. This article has provided an overview of some common list operations and demonstrated how to use lambda expressions to perform them, along with more than 26 code samples to illustrate their usage.

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