/*

LINQ includes five sorting operators: OrderBy, OrderByDescending, ThenBy, ThenByDescending and Reverse

LINQ query syntax does not support OrderByDescending, ThenBy, ThenByDescending and Reverse. It only supports 'Order By' clause with 'ascending' and 'descending' sorting direction.

LINQ query syntax supports multiple sorting fields seperated by comma whereas you have to use ThenBy & ThenByDescending methods for secondary sorting.

​

OrderBy and ThenBy sorts collections in ascending order by default.

ThenBy or ThenByDescending is used for second level sorting in method syntax.

ThenByDescending method sorts the collection in decending order on another field.

ThenBy or ThenByDescending is NOT applicable in Query syntax.

Apply secondary sorting in query syntax by separating fields using comma.

​

*/

​

using System;

using System.Linq;

using System.Collections.Generic;

​

class ImageData

{

    public string FileName { get; set; }

    public DateTime LastModified { get; set; }

    public int FileSizeInKB { get; set; }

}

​

public class Program

{

    public static void Main()

    {   

        IList<ImageData> imageList = new List<ImageData>() 

        { 

            new ImageData() { FileName="Flower.Jpg", LastModified =  DateTime.Parse("1/1/2022"), FileSizeInKB = 10} ,

            new ImageData() { FileName="Flower.gif", LastModified =  DateTime.Parse("1/1/2022"), FileSizeInKB = 500} ,

            new ImageData() { FileName="Flower.bmp", LastModified =  DateTime.Parse("1/1/2022"), FileSizeInKB = 200} ,          

        };

​

        //OrderBy, OrderByDescending, ThenBy, ThenByDescending  - Method Syntax

        //Use ThenBy for multiple field sorting.

        Console.WriteLine("OrderBy, ThenBy - Method Syntax\n -------------------------------" );

        var result = imageList.OrderByDescending(s => s.LastModified).ThenByDescending(s => s.FileSizeInKB);

        foreach (ImageData std in result)

        {

            Console.WriteLine(std.FileName + " - " + std.LastModified + " - " + std.FileSizeInKB);

        }   

        var lastUpdated = imageList.OrderByDescending(s => s.LastModified).ThenByDescending(s => s.FileSizeInKB).FirstOrDefault();

        Console.WriteLine("\n\nLast Modified Image\n______________________________________");

        Console.WriteLine(lastUpdated.FileName + " - " + lastUpdated.LastModified + " - " + lastUpdated.FileSizeInKB);

    }

}