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Queryable.ThenBy<TSource, TKey> Method (IOrderedQueryable<TSource>, Expression<Func<TSource, TKey>>, IComparer<TKey>)

Performs a subsequent ordering of the elements in a sequence in ascending order by using a specified comparer.

Namespace:  System.Linq
Assemblies:   System.Linq.Queryable (in System.Linq.Queryable.dll)
  System.Core (in System.Core.dll)

public static IOrderedQueryable<TSource> ThenBy<TSource, TKey>(
	this IOrderedQueryable<TSource> source,
	Expression<Func<TSource, TKey>> keySelector,
	IComparer<TKey> comparer
)

Type Parameters

TSource

The type of the elements of source.

TKey

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

Parameters

source
Type: System.Linq.IOrderedQueryable<TSource>

An IOrderedQueryable<T> that contains elements to sort.

keySelector
Type: System.Linq.Expressions.Expression<Func<TSource, TKey>>

A function to extract a key from each element.

comparer
Type: System.Collections.Generic.IComparer<TKey>

An IComparer<T> to compare keys.

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 IOrderedQueryable<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
ArgumentNullException

source or keySelector or comparer 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 ThenBy<TSource, TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource, TKey>>, IComparer<TKey>) method generates a MethodCallExpression that represents calling ThenBy<TSource, TKey>(IOrderedQueryable<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 ThenBy<TSource, TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource, TKey>>, IComparer<TKey>) depends on the implementation of the type of the source parameter. The expected behavior is that it performs a secondary sort of the elements of source based on the key obtained by invoking keySelector on each element of source. All previously established sort orders are preserved. The comparer parameter is used to compare key values.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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