Orderby

In C# an orderby clause adds sorting to a query. It imposes a sorting algorithm to the expression's result. It can be placed within a query that also does other things.

In the C# language, the "orderby" clause is compiled to the OrderBy method. Often the clearest way to use the LINQ OrderBy method is with a clause.

First example

The "using System.Linq" directive is present at the top. The 3 query expressions use an orderby element, orderby element ascending, and orderby element descending syntax.

using System;
using System.Linq;

// Input array.
int[] array = { 2, 5, 3 };
// Use orderby, orderby ascending, and orderby descending.
var result0 = from element in array
              orderby element
              select element;

var result1 = from element in array
              orderby element ascending
              select element;

var result2 = from element in array
              orderby element descending
              select element;
// Print results.
Console.WriteLine("result0");
foreach (var element in result0)
{
    Console.WriteLine(element);
}
Console.WriteLine("result1");
foreach (var element in result1)
{
    Console.WriteLine(element);
}
Console.WriteLine("result2");
foreach (var element in result2)
{
    Console.WriteLine(element);
}
result0
2
3
5
result1
2
3
5
result2
5
3
2

Compiler

How are the orderby clauses in the expressions compiled to the intermediate form? The C# specification describes how the query clauses are translated into extension method calls.

With query expressions, the foreach-statement evaluates the queries as we loop over them. The can be considered fully lazy in this way.

A summary

We used query expressions with ascending and descending, resulting in 3 sorted and enumerable collections. We examined the query syntax intermediate form.