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Sorting Data

Visual Studio 2010

A sorting operation orders the elements of a sequence based on one or more attributes. The first sort criterion performs a primary sort on the elements. By specifying a second sort criterion, you can sort the elements within each primary sort group.

The following illustration shows the results of an alphabetical sort operation on a sequence of characters.

The standard query operator methods that sort data are listed in the following section.

Methods

Method Name	Description	C# Query Expression Syntax	Visual Basic Query Expression Syntax	More Information
OrderBy	Sorts values in ascending order.	orderby	Order By	Enumerable.OrderBy Queryable.OrderBy
OrderByDescending	Sorts values in descending order.	orderby … descending	Order By … Descending	Enumerable.OrderByDescending Queryable.OrderByDescending
ThenBy	Performs a secondary sort in ascending order.	orderby …, …	Order By …, …	Enumerable.ThenBy Queryable.ThenBy
ThenByDescending	Performs a secondary sort in descending order.	orderby …, … descending	Order By …, … Descending	Enumerable.ThenByDescending Queryable.ThenByDescending
Reverse	Reverses the order of the elements in a collection.	Not applicable.	Not applicable.	Enumerable.Reverse<TSource> Queryable.Reverse<TSource>

Query Expression Syntax Examples

Primary Sort Examples

Primary Ascending Sort

The following example demonstrates how to use the orderby (Order By in Visual Basic) clause in a LINQ query to sort the strings in an array by string length, in ascending order.



            string[] words = { "the", "quick", "brown", "fox", "jumps" };

            IEnumerable<string> query = from word in words
                                        orderby word.Length
                                        select word;

            foreach (string str in query)
                Console.WriteLine(str);

            /* This code produces the following output:

                the
                fox
                quick
                brown
                jumps
            */

Primary Descending Sort

The next example demonstrates how to use the orderby descending (Order By Descending in Visual Basic) clause in a LINQ query to sort the strings by their first letter, in descending order.



            string[] words = { "the", "quick", "brown", "fox", "jumps" };

            IEnumerable<string> query = from word in words
                                        orderby word.Substring(0, 1) descending
                                        select word;

            foreach (string str in query)
                Console.WriteLine(str);

            /* This code produces the following output:

                the
                quick
                jumps
                fox
                brown
            */

Secondary Sort Examples

Secondary Ascending Sort

The following example demonstrates how to use the orderby (Order By in Visual Basic) clause in a LINQ query to perform a primary and secondary sort of the strings in an array. The strings are sorted primarily by length and secondarily by the first letter of the string, both in ascending order.



            string[] words = { "the", "quick", "brown", "fox", "jumps" };

            IEnumerable<string> query = from word in words
                                        orderby word.Length, word.Substring(0, 1)
                                        select word;

            foreach (string str in query)
                Console.WriteLine(str);

            /* This code produces the following output:

                fox
                the
                brown
                jumps
                quick
            */

Secondary Descending Sort

The next example demonstrates how to use the orderby descending (Order By Descending in Visual Basic) clause in a LINQ query to perform a primary sort, in ascending order, and a secondary sort, in descending order. The strings are sorted primarily by length and secondarily by the first letter of the string.



            string[] words = { "the", "quick", "brown", "fox", "jumps" };

            IEnumerable<string> query = from word in words
                                        orderby word.Length, word.Substring(0, 1) descending
                                        select word;

            foreach (string str in query)
                Console.WriteLine(str);

            /* This code produces the following output:

                the
                fox
                quick
                jumps
                brown
            */

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