Part 73 - What is dictionary in c# continued

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Part 70 - Making method parameters optional by using OptionalAttribute
Part 71 - Code snippets in visual studio
Part 72 - What is dictionary in c#



Please watch Part 72 from the c# tutorial before proceeding with this video. This is a continuation to Part 72.

In this video, we will discuss the following methods of Dictionary class.
1. TryGetValue()
2. Count()
3. Remove()
4. Clear()
5. Using LINQ extension methods with Dictionary
6. Different ways to convert an array into a dictionary



Code used in the demo:
public class Program
{
    public static void Main()
    {
        // Create Customer Objects
        Customer customr1 = new Customer()
        {
            ID = 101,
            Name = "Mark",
            Salary = 5000
        };

        Customer customr2 = new Customer()
        {
            ID = 102,
            Name = "Pam",
            Salary = 7000
        };

        Customer customr3 = new Customer()
        {
            ID = 104,
            Name = "Rob",
            Salary = 5500
        };

        // Create a Dictionary, CustomerID is the key. Type is int
        // Customer object is the value. Type is Customer
        Dictionary<int, Customer> dictionaryCustomers = new Dictionary<int, Customer>();

        // Add customer objects to the dictionary
        dictionaryCustomers.Add(customr1.ID, customr1);
        dictionaryCustomers.Add(customr2.ID, customr2);
        dictionaryCustomers.Add(customr3.ID, customr3);

        // If you are not sure if a key is present or not, you can use 
        // TryGetValue() method to get the value from a dictionary.
        Customer customer999;
        if (dictionaryCustomers.TryGetValue(999, out customer999))
        {
            Console.WriteLine("ID = {0}, Name = {1}, Salary = {2}", customer999.ID, customer999.Name, customer999.Salary);
        }
        else
        {
            Console.WriteLine("Customer with Key = 999 is not found in the dictionary");
            Console.WriteLine("-------------------------------------------------------------------");
        }

        // To find the total number of items in a dictionary use Count() method
        Console.WriteLine("Total items in Dictionary = {0}", dictionaryCustomers.Count());
        Console.WriteLine("-------------------------------------------------------------------");

        // LINQ extension methods can be used with Dictionary. For example, to find the 
        // total employees whose salary is greater than 5000.
        Console.WriteLine("Items in dictionary where Salary is greater than 5000 = {0}",
            dictionaryCustomers.Count(x => x.Value.Salary > 5000));
        Console.WriteLine("-------------------------------------------------------------------");

        // To remove an item from the dictionary, use Remove() method
        dictionaryCustomers.Remove(101);

        // To remove all items from the dictionary, use Clear() method
        dictionaryCustomers.Clear();

        // Create an array of customers
        Customer[] arrayCustomers = new Customer[3];
        arrayCustomers[0] = customr1;
        arrayCustomers[1] = customr2;
        arrayCustomers[2] = customr3;

        // Convert customer array to a dictionary using ToDictionary() method.
        // In this example, key is Customer ID and value is the customer object
        Dictionary<int, Customer> dict = arrayCustomers.ToDictionary(customer => customer.ID, customer => customer);
        // OR        
        // Dictionary<int, Customr> dict = arrayCustomers.ToDictionary(customer => customer.ID);
        // OR use a foreach loop
        // Dictionary<int, Customer> dict = new Dictionary<int, Customer>();
        // foreach (Customer cust in arrayCustomers)
        // {
        //     dict.Add(cust.ID, cust);
        // }

        // Loop thru the dictionary and print the key/value pairs
        foreach (KeyValuePair<int, Customer> kvp in dict)
        {
            Console.WriteLine("Key = {0}", kvp.Key);
            Customer customr = kvp.Value;
            Console WriteLine("ID = {0}, Name = {1}, Salary {2}", customr.ID, customr.Name, customr.Salary);
        }
        Console.WriteLine("-------------------------------------------------------------------");
    }
}

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