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Queryable.OrderBy<TSource, TKey> Method (IQueryable<TSource>, Expression<Func<TSource, TKey>>)

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

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)

public static IOrderedQueryable<TSource> OrderBy<TSource, TKey>(
	this IQueryable<TSource> source,
	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
Type: System.Linq.IQueryable<TSource>
A sequence of values to order.
keySelector
Type: System.Linq.Expressions.Expression<Func<TSource, TKey>>
A function to extract a key from an element.

Return Value

Type: System.Linq.IOrderedQueryable<TSource>
An IOrderedQueryable<T> whose elements are sorted according to a key.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<TSource>. When you use instance method syntax to call this method, omit the first parameter.

ExceptionCondition
ArgumentNullException

source or keySelector is null.

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.

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


         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)
               outputBlock.Text += String.Format("{0} - {1}", pet.Name, pet.Age) + "\n";
         }

         /*
             This code produces the following output:

             Whiskers - 1
             Boots - 4
             Barley - 8
         */



Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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