Part 75 - List collection class in c# continued

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Part 72 - What is dictionary in c#
Part 73 - What is dictionary in c# continued
Part 74 - List collection class in c#



This is continuation to Part 74. So, please watch Part 74, before proceeding. In this video, we will discuss
1. Contains() function - Use this function to check if an item exists in the list. This method returns true if the items exists, else false.

2. Exists() function - Use this function, to check if an item exists in the list based on a condition. This method returns true if the items exists, else false.

3. Find() function - This method searches for an element that matches the conditions defined by the specified lambda expression and returns the first matching item from the list.

4. FindLast() function - This method searches for an element that matches the conditions defined by the specified lambda expression and returns the Last matching item from the list.

5. FindAll() function - This method returns all the items from the list that match the conditions specified by the lambda expression.



6. FindIndex() function - This method returns the index of the first item, that matches the condition specified by the lambda expression. There are 2 other overloads of this method which allows us to specify the range of elements to search, with in the list.

7. FindLastIndex() function - This method returns the index of the last item, that matches the condition specified by the lambda expression. There are 2 other overloads of this method which allows us to specify the range of elements to search, with in the list.

8. Convert an array to a List - Use ToList() method

9. Convert a list to an array - Use ToArray() method

10. Convert a List to a Dictionary - Use ToDictionary() method

public class Program
{
    public static void Main()
    {
        // Create Customer Objects
        Customer customer1 = new Customer()
        {
            ID = 101,
            Name = "Mark",
            Salary = 4000
        };

        Customer customer2 = new Customer()
        {
            ID = 102,
            Name = "Pam",
            Salary = 7000
        };

        Customer customer3 = new Customer()
        {
            ID = 104,
            Name = "Rob",
            Salary = 5500
        };

        Customer[] arrayCustomers = new Customer[3];
        arrayCustomers[0] = customer1;
        arrayCustomers[1] = customer2;
        arrayCustomers[2] = customer3;

        // To convert an array to a List, use ToList() method
        List<Customer> listCustomers = arrayCustomers.ToList();
        foreach (Customer c in listCustomers)
        {
            Console.WriteLine("ID = {0}, Name = {1}, Salary = {2}", c.ID, c.Name, c.Salary);
        }
        Console.WriteLine("------------------------------------------------------");

        // To convert a List to an array, use ToLArray() method
        Customer[] arrayAllCustomers = listCustomers.ToArray();
        foreach (Customer c in arrayAllCustomers)
        {
            Console.WriteLine("ID = {0}, Name = {1}, Salary = {2}", c.ID, c.Name, c.Salary);
        }
        Console.WriteLine("------------------------------------------------------");

        // To convert a List to a Dictionary use ToDictionary() method
        Dictionary<int, Customer> dictionaryCustomers = listCustomers.ToDictionary(x => x.ID);
        foreach (KeyValuePair<int, Customer> keyValuePairCustomers in dictionaryCustomers)
        {
            Console.WriteLine("Key = {0}", keyValuePairCustomers.Key);
            Customer c = keyValuePairCustomers.Value;
            Console.WriteLine("ID = {0}, Name = {1}, Salary = {2}", c.ID, c.Name, c.Salary);
        }
        Console.WriteLine("------------------------------------------------------");

        // To check if an item exists in the list use Contains() function
        // This method returns true if the items exists, else false
        if (listCustomers.Contains(customer2))
        {
            Console.WriteLine("Customer2 object exists in the list");
        }
        else
        {
            Console.WriteLine("Customer2 object does not exist in the list");
        }
        Console.WriteLine("------------------------------------------------------");

        // To check if an item exists in the list based on a condition, then use Exists() function
        // This method returns true if the items exists, else false
        if (listCustomers.Exists(x => x.Name.StartsWith("M")))
        {
            Console.WriteLine("List contains customer whose name starts with M");
        }
        else
        {
            Console.WriteLine("List does not contain a customer whose name starts with M");
        }
        Console.WriteLine("------------------------------------------------------");

        // Find() method searches for an element that matches the conditions defined by 
        // the specified lambda expression and returns the first matching item from the list
        Customer cust = listCustomers.Find(customer => customer.Salary > 5000);
        Console.WriteLine("ID = {0}, Name = {1}, Salary = {2}", cust.ID, cust.Name, cust.Salary);
        Console.WriteLine("------------------------------------------------------");

        // FindLast() method searches for an element that matches the conditions defined
        // by the specified lambda expression and returns the Last matching item from the list
        Customer lastMatch = listCustomers.FindLast(customer => customer.Salary > 5000);
        Console WriteLine("ID = {0}, Name = {1}, Salary = {2}", lastMatch.ID, lastMatch.Name, lastMatch.Salary);
        Console.WriteLine("------------------------------------------------------");

        // FindAll() method returns all the items from the list that
        // match the conditions specified by the lambda expression
        List<Customer> filteredCustomers = listCustomers.FindAll(customer => customer.Salary > 5000);
        foreach (Customer cstmr in filteredCustomers)
        {
            Console.WriteLine("ID = {0}, Name = {1}, Salary = {2}", cstmr.ID, cstmr.Name, cstmr.Salary);
        }
        Console.WriteLine("------------------------------------------------------");

        // FindIndex() method returns the index of the first item, that matches the 
        // condition specified by the lambda expression. There are 2 other overloads
        // of this method which allows us to specify the range of elements to 
        // search, with in the list.
        Console.WriteLine("Index of the first matching customer object whose salary is greater 5000 =" +
            listCustomers.FindIndex(customer => customer.Salary > 5000));
        Console.WriteLine("------------------------------------------------------");

        // FindLastIndex() method returns the index of the last item, 
        // that matches the condition specified by the lambda expression. 
        // There are 2 other overloads of this method which allows us to specify 
        // the range of elements to search, with in the list.
        Console.WriteLine("Index of the Last matching customer object whose salary is greater 5000 = " +
            listCustomers.FindLastIndex(customer => customer.Salary > 5000));
        Console.WriteLine("------------------------------------------------------");
    }
}

public class Customer
{
    public int ID { get; set; }
    public string Name { get; set; }
    public int Salary { get; set; }
}