/*
* 1. One of the overload of the sort() method in list class expects Comparision delegate to be passes as an argument.
*
* 2. Approach 1.
* Step 1: Create a fnction whose signature mathches the signature of System.Comparison delegate.
* Comparison() is the method we need to write logic to compare 2 customer objects.
* Step 2: Create an instance of System.Comparision delegate and then pass the name of the function created in Step 1 as the argument.
* So, at this point "Comparison" delegate is pointing to our function that contains the logic to compare 2 customer objects.
* Step 3: Pass the delegate instance as an argument, to Sort() function.
*
* 3. Approach 2.
* All the steps in approach 1 can be replaced by simply writing delegate keyword and logic in Sort() function.
*
* 4. Approach 3.
* By using lamda expression.
*/
static void Main(string[] args)
{
Customer customer1 = new Customer() { ID = 101, Name = "Anand Dev", Salary = 4000 };
Customer customer2 = new Customer() { ID = 102, Name = "Nanhi", Salary = 8000 };
Customer customer3 = new Customer() { ID = 103, Name = "Praveen", Salary = 6000 };
List<Customer> listCustomers = new List<Customer>();
listCustomers.Add(customer1);
listCustomers.Add(customer3);
listCustomers.Add(customer2);
Console.WriteLine("Before sorting.");
foreach (Customer c in listCustomers)
{
Console.WriteLine("ID = {0}, Name = {1}.", c.ID, c.Name);
}
#region 1. Approach 1 - Step 2 and 3.
// Step 2.
Comparison<Customer> customerComparer = new Comparison<Customer>(Comparison);
// Step 3.
listCustomers.Sort(customerComparer);
Console.WriteLine("\nAfter sorting by ID ASC using Comparison delegate - Approach 1");
foreach (Customer c in listCustomers)
{
Console.WriteLine("ID = {0}, Name = {1}.", c.ID, c.Name);
}
#endregion
#region 2. Approach 2 - By implemention delegate directly in Sort() function.
Customer customer4 = new Customer() { ID = 104, Name = "Jam", Salary = 4000 };
Customer customer5 = new Customer() { ID = 105, Name = "Mark", Salary = 8000 };
Customer customer6 = new Customer() { ID = 106, Name = "Odi", Salary = 6000 };
List<Customer> listCustomers2 = new List<Customer>();
listCustomers2.Add(customer6);
listCustomers2.Add(customer4);
listCustomers2.Add(customer5);
Console.WriteLine("\nBefore sorting.");
foreach (Customer c in listCustomers2)
{
Console.WriteLine("ID = {0}, Name = {1}.", c.ID, c.Name);
}
Console.WriteLine("Second way.");
listCustomers2.Sort(delegate(Customer c1, Customer c2) { return c1.ID.CompareTo(c2.ID); });
Console.WriteLine("\nAfter sorting by ID ASC using Comparison delegate - Approach 2");
foreach (Customer c in listCustomers2)
{
Console.WriteLine("ID = {0}, Name = {1}.", c.ID, c.Name);
}
#endregion
#region 3. Approach 3 - By using lamda expression.
List<Customer> listAllCustomers = new List<Customer>();
listAllCustomers.AddRange(listCustomers);
listAllCustomers.AddRange(listCustomers2);
Console.WriteLine("\nBefore sorting.");
foreach (Customer c in listAllCustomers)
{
Console.WriteLine("ID = {0}, Name = {1}.", c.ID, c.Name);
}
listAllCustomers.Sort((x, y) => x.ID.CompareTo(y.ID));
Console.WriteLine("\nAfter sorting using lamda expression - Approach 3.");
foreach (Customer c in listAllCustomers)
{
Console.WriteLine("ID = {0}, Name = {1}.", c.ID, c.Name);
}
#endregion
Console.ReadKey();
}
// Step 1.
private static int Comparison(Customer x, Customer y)
{
return x.ID.CompareTo(y.ID);
}