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EnumerableRowCollectionExtensions.ThenByDescending<TRow, TKey> Method (OrderedEnumerableRowCollection<TRow>, Func<TRow, TKey>, IComparer<TKey>)

Performs a secondary ordering of the rows of a EnumerableRowCollection in descending order according to the specified key and comparer. This API supports the .NET Framework infrastructure and is not intended to be used directly from your code.

Namespace:  System.Data
Assembly:  System.Data.DataSetExtensions (in System.Data.DataSetExtensions.dll)

public static OrderedEnumerableRowCollection<TRow> ThenByDescending<TRow, TKey>(
	this OrderedEnumerableRowCollection<TRow> source,
	Func<TRow, TKey> keySelector,
	IComparer<TKey> comparer

Type Parameters


The type of the row elements in source, typically DataRow.


The type of the key returned by keySelector.


Type: System.Data.OrderedEnumerableRowCollection<TRow>
An EnumerableRowCollection containing the DataRow elements to be ordered.
Type: System.Func<TRow, TKey>
A function to extract a key from an element.
Type: System.Collections.Generic.IComparer<TKey>
An IComparer<T> to compare keys.

Return Value

Type: System.Data.OrderedEnumerableRowCollection<TRow>
An OrderedEnumerableRowCollection<TRow> whose elements are sorted by the specified key and comparer.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type OrderedEnumerableRowCollection<TRow>. 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).

The use of a ThenByDescending operation requires an existing primary sorting operation using OrderBy.

This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

.NET Framework

Supported in: 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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