Queryable.OrderBy Method

Definition

Namespace:

System.Linq

Assemblies:

netstandard.dll, System.Linq.Queryable.dll

Sorts the elements of a sequence in ascending order.

Overloads

OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)	Sorts the elements of a sequence in ascending order according to a key.
OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)	Sorts the elements of a sequence in ascending order by using a specified comparer.

OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)

Source:

Queryable.cs

Sorts the elements of a sequence in ascending order according to a key.

C#

public static System.Linq.IOrderedQueryable<TSource> OrderBy<TSource,TKey>(this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector);

Type Parameters

TSource

The type of the elements of source.

TKey

The type of the key returned by the function that is represented by keySelector.

Parameters

source

IQueryable<TSource>

A sequence of values to order.

keySelector

Expression<Func<TSource,TKey>>

A function to extract a key from an element.

Returns

IOrderedQueryable<TSource>

An IOrderedQueryable<T> whose elements are sorted according to a key.

Exceptions

ArgumentNullException

source or keySelector is null.

Examples

The following code example demonstrates how to use OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) to sort the elements of a sequence.

C#

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void OrderByEx1()
{
    Pet[] pets = { new Pet { Name="Barley", Age=8 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=1 } };

    // Sort the Pet objects in the array by Pet.Age.
    IEnumerable<Pet> query =
        pets.AsQueryable().OrderBy(pet => pet.Age);

    foreach (Pet pet in query)
        Console.WriteLine("{0} - {1}", pet.Name, pet.Age);
}

/*
    This code produces the following output:

    Whiskers - 1
    Boots - 4
    Barley - 8
*/

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) method generates a MethodCallExpression that represents calling OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. The result of calling CreateQuery<TElement>(Expression) is cast to type IOrderedQueryable<T> and returned.

The query behavior that occurs as a result of executing an expression tree that represents calling OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) depends on the implementation of the type of the source parameter. The expected behavior is that it sorts the elements of source based on the key obtained by invoking keySelector on each element of source.

OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)

Source:

Queryable.cs

Sorts the elements of a sequence in ascending order by using a specified comparer.

C#

public static System.Linq.IOrderedQueryable<TSource> OrderBy<TSource,TKey>(this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Collections.Generic.IComparer<TKey>? comparer);

Type Parameters

TSource

The type of the elements of source.

TKey

The type of the key returned by the function that is represented by keySelector.

Parameters

source

IQueryable<TSource>

A sequence of values to order.

keySelector

Expression<Func<TSource,TKey>>

A function to extract a key from an element.

comparer

IComparer<TKey>

An IComparer<T> to compare keys.

Returns

IOrderedQueryable<TSource>

An IOrderedQueryable<T> whose elements are sorted according to a key.

Exceptions

ArgumentNullException

source or keySelector or comparer is null.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) method generates a MethodCallExpression that represents calling OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. The result of calling CreateQuery<TElement>(Expression) is cast to type IOrderedQueryable<T> and returned.

The query behavior that occurs as a result of executing an expression tree that represents calling OrderBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) depends on the implementation of the type of the source parameter. The expected behavior is that it sorts the elements of source based on the key obtained by invoking keySelector on each element of source. The comparer parameter is used to compare keys.