Enumerable.OrderByDescending Enumerable.OrderByDescending Enumerable.OrderByDescending Enumerable.OrderByDescending Method

Definición

Ordena de manera descendente los elementos de una secuencia.Sorts the elements of a sequence in descending order.

Sobrecargas

OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)

Ordena de manera descendente los elementos de una secuencia utilizando un comparador especificado.Sorts the elements of a sequence in descending order by using a specified comparer.

OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Ordena de manera descendente los elementos de una secuencia en función de una clave.Sorts the elements of a sequence in descending order according to a key.

OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)

Ordena de manera descendente los elementos de una secuencia utilizando un comparador especificado.Sorts the elements of a sequence in descending order by using a specified comparer.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IOrderedEnumerable<TSource> ^ OrderByDescending(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, System::Collections::Generic::IComparer<TKey> ^ comparer);
public static System.Linq.IOrderedEnumerable<TSource> OrderByDescending<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, System.Collections.Generic.IComparer<TKey> comparer);
static member OrderByDescending : seq<'Source> * Func<'Source, 'Key> * System.Collections.Generic.IComparer<'Key> -> System.Linq.IOrderedEnumerable<'Source>
<Extension()>
Public Function OrderByDescending(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), comparer As IComparer(Of TKey)) As IOrderedEnumerable(Of TSource)

Parámetros de tipo

TSource

Tipo de los elementos de source.The type of the elements of source.

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

Parámetros

source
IEnumerable<TSource>

Secuencia de valores que se va a ordenar.A sequence of values to order.

keySelector
Func<TSource,TKey>

Función para extraer una clave a partir de un elemento.A function to extract a key from an element.

comparer
IComparer<TKey>

IComparer<T> para comparar claves.An IComparer<T> to compare keys.

Devoluciones

Una interfaz IOrderedEnumerable<TElement> cuyos elementos se ordenan de manera descendente con arreglo a una clave.An IOrderedEnumerable<TElement> whose elements are sorted in descending order according to a key.

Excepciones

source o keySelector es null.source or keySelector is null.

Ejemplos

En el ejemplo de código siguiente se muestra cómo usar OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>) para ordenar los elementos de una secuencia en orden descendente mediante una función de transformación y un comparador personalizado.The following code example demonstrates how to use OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>) to sort the elements of a sequence in descending order by using a transform function and a custom comparer.

/// <summary>
/// This IComparer class sorts by the fractional part of the decimal number.
/// </summary>
public class SpecialComparer : IComparer<decimal>
{
    /// <summary>
    /// Compare two decimal numbers by their fractional parts.
    /// </summary>
    /// <param name="d1">The first decimal to compare.</param>
    /// <param name="d2">The second decimal to compare.</param>
    /// <returns>1 if the first decimal's fractional part 
    /// is greater than the second decimal's fractional part,
    /// -1 if the first decimal's fractional
    /// part is less than the second decimal's fractional part,
    /// or the result of calling Decimal.Compare()
    /// if the fractional parts are equal.</returns>
    public int Compare(decimal d1, decimal d2)
    {
        decimal fractional1, fractional2;

        // Get the fractional part of the first number.
        try
        {
            fractional1 = decimal.Remainder(d1, decimal.Floor(d1));
        }
        catch (DivideByZeroException)
        {
            fractional1 = d1;
        }
        // Get the fractional part of the second number.
        try
        {
            fractional2 = decimal.Remainder(d2, decimal.Floor(d2));
        }
        catch (DivideByZeroException)
        {
            fractional2 = d2;
        }

        if (fractional1 == fractional2)
            return Decimal.Compare(d1, d2);
        else if (fractional1 > fractional2)
            return 1;
        else
            return -1;
    }
}

public static void OrderByDescendingEx1()
{
    List<decimal> decimals =
        new List<decimal> { 6.2m, 8.3m, 0.5m, 1.3m, 6.3m, 9.7m };

    IEnumerable<decimal> query =
        decimals.OrderByDescending(num =>
                                       num, new SpecialComparer());

    foreach (decimal num in query)
    {
        Console.WriteLine(num);
    }
}

/*
 This code produces the following output:

 9.7
 0.5
 8.3
 6.3
 1.3
 6.2
*/
' This class provides a custom implementation 
' of the IComparer.Compare() method.
Class SpecialComparer
    Implements IComparer(Of Decimal)
    ''' <summary>
    ''' Compare two decimal numbers by their fractional parts.
    ''' </summary>
    ''' <param name="d1">The first decimal to compare.</param>
    ''' <param name="d2">The second decimal to compare.</param>
    ''' <returns>1 if the first decimal's fractional part is greater than
    ''' the second decimal's fractional part,
    ''' -1 if the first decimal's fractional
    ''' part is less than the second decimal's fractional part,
    ''' or the result of calling Decimal.Compare()
    ''' if the fractional parts are equal.</returns>
    Function Compare(ByVal d1 As Decimal, ByVal d2 As Decimal) As Integer _
    Implements IComparer(Of Decimal).Compare

        Dim fractional1 As Decimal
        Dim fractional2 As Decimal

        ' Get the fractional part of the first number.
        Try
            fractional1 = Decimal.Remainder(d1, Decimal.Floor(d1))
        Catch ex As DivideByZeroException
            fractional1 = d1
        End Try

        ' Get the fractional part of the second number.
        Try
            fractional2 = Decimal.Remainder(d2, Decimal.Floor(d2))
        Catch ex As DivideByZeroException
            fractional2 = d2
        End Try

        If (fractional1 = fractional2) Then
            ' The fractional parts are equal, so compare the entire numbers.
            Return Decimal.Compare(d1, d2)
        ElseIf (fractional1 > fractional2) Then
            Return 1
        Else
            Return -1
        End If
    End Function
End Class

Sub OrderByDescendingEx1()
    ' Create a list of decimal values.
    Dim decimals As New List(Of Decimal)(New Decimal() _
                                     {6.2D, 8.3D, 0.5D, 1.3D, 6.3D, 9.7D})

    ' Order the elements of the list by passing
    ' in the custom IComparer class.
    Dim query As IEnumerable(Of Decimal) =
    decimals.OrderByDescending(Function(num) num,
                               New SpecialComparer())

    Dim output As New System.Text.StringBuilder
    For Each num As Decimal In query
        output.AppendLine(num)
    Next

    ' Display the output.
    MsgBox(output.ToString())
End Sub

' This code produces the following output:
'
' 9.7
' 0.5
' 8.3
' 6.3
' 1.3
' 6.2

Comentarios

Este método se implementa mediante la ejecución aplazada.This method is implemented by using deferred execution. El valor devuelto inmediato es un objeto que almacena toda la información necesaria para realizar la acción.The immediate return value is an object that stores all the information that is required to perform the action. La consulta representada por este método no se ejecuta hasta que se enumera el objeto llamando a su GetEnumerator método directamente o mediante foreach en Visual C# o For Each en Visual Basic.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.

Para ordenar una secuencia por los valores de los propios elementos, especifique la función identity (x => x en Visual C# o Function(x) x en Visual Basic) para keySelector.To order a sequence by the values of the elements themselves, specify the identity function (x => x in Visual C# or Function(x) x in Visual Basic) for keySelector.

Se definen dos métodos para ampliar el tipo IOrderedEnumerable<TElement>, que es el tipo de valor devuelto de este método.Two methods are defined to extend the type IOrderedEnumerable<TElement>, which is the return type of this method. Estos dos métodos, es decir, ThenBy y ThenByDescending, le permiten especificar los criterios de ordenación adicionales para ordenar una secuencia.These two methods, namely ThenBy and ThenByDescending, enable you to specify additional sort criteria to sort a sequence. ThenBy y ThenByDescending también devuelven un IOrderedEnumerable<TElement>, lo que significa que cualquier número de llamadas consecutivas a ThenBy o ThenByDescending se pueden realizar.ThenBy and ThenByDescending also return an IOrderedEnumerable<TElement>, which means any number of consecutive calls to ThenBy or ThenByDescending can be made.

Nota

Dado que IOrderedEnumerable<TElement> hereda IEnumerable<T>, puede llamar a OrderBy o OrderByDescending en los resultados de una llamada a OrderBy, OrderByDescending, ThenBy o ThenByDescending.Because IOrderedEnumerable<TElement> inherits from IEnumerable<T>, you can call OrderBy or OrderByDescending on the results of a call to OrderBy, OrderByDescending, ThenBy or ThenByDescending. Esto presenta un nuevo orden primario que omite el orden establecido previamente.Doing this introduces a new primary ordering that ignores the previously established ordering.

Si comparer es null, el comparador predeterminado Default se utiliza para comparar claves.If comparer is null, the default comparer Default is used to compare keys.

Este método realiza a una ordenación estable; es decir, si las claves de dos elementos son iguales, se conserva el orden de los elementos.This method performs a stable sort; that is, if the keys of two elements are equal, the order of the elements is preserved. En cambio, una ordenación inestable no conserva el orden de los elementos que tienen la misma clave.In contrast, an unstable sort does not preserve the order of elements that have the same key.

Consulte también:

OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Ordena de manera descendente los elementos de una secuencia en función de una clave.Sorts the elements of a sequence in descending order according to a key.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IOrderedEnumerable<TSource> ^ OrderByDescending(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector);
public static System.Linq.IOrderedEnumerable<TSource> OrderByDescending<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector);
static member OrderByDescending : seq<'Source> * Func<'Source, 'Key> -> System.Linq.IOrderedEnumerable<'Source>
<Extension()>
Public Function OrderByDescending(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey)) As IOrderedEnumerable(Of TSource)

Parámetros de tipo

TSource

Tipo de los elementos de source.The type of the elements of source.

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

Parámetros

source
IEnumerable<TSource>

Secuencia de valores que se va a ordenar.A sequence of values to order.

keySelector
Func<TSource,TKey>

Función para extraer una clave a partir de un elemento.A function to extract a key from an element.

Devoluciones

Una interfaz IOrderedEnumerable<TElement> cuyos elementos se ordenan de manera descendente con arreglo a una clave.An IOrderedEnumerable<TElement> whose elements are sorted in descending order according to a key.

Excepciones

source o keySelector es null.source or keySelector is null.

Comentarios

Este método se implementa mediante la ejecución aplazada.This method is implemented by using deferred execution. El valor devuelto inmediato es un objeto que almacena toda la información necesaria para realizar la acción.The immediate return value is an object that stores all the information that is required to perform the action. La consulta representada por este método no se ejecuta hasta que se enumera el objeto llamando a su GetEnumerator método directamente o mediante foreach en Visual C# o For Each en Visual Basic.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.

Para ordenar una secuencia por los valores de los propios elementos, especifique la función identity (x => x en Visual C# o Function(x) x en Visual Basic) para keySelector.To order a sequence by the values of the elements themselves, specify the identity function (x => x in Visual C# or Function(x) x in Visual Basic) for keySelector.

Para obtener un ejemplo de este método, consulte OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>).For an example of this method, see OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>).

Se definen dos métodos para ampliar el tipo IOrderedEnumerable<TElement>, que es el tipo de valor devuelto de este método.Two methods are defined to extend the type IOrderedEnumerable<TElement>, which is the return type of this method. Estos dos métodos, es decir, ThenBy y ThenByDescending, le permiten especificar los criterios de ordenación adicionales para ordenar una secuencia.These two methods, namely ThenBy and ThenByDescending, enable you to specify additional sort criteria to sort a sequence. ThenBy y ThenByDescending también devuelven un IOrderedEnumerable<TElement>, lo que significa que cualquier número de llamadas consecutivas a ThenBy o ThenByDescending se pueden realizar.ThenBy and ThenByDescending also return an IOrderedEnumerable<TElement>, which means any number of consecutive calls to ThenBy or ThenByDescending can be made.

Nota

Dado que IOrderedEnumerable<TElement> hereda IEnumerable<T>, puede llamar a OrderBy o OrderByDescending en los resultados de una llamada a OrderBy, OrderByDescending, ThenBy o ThenByDescending.Because IOrderedEnumerable<TElement> inherits from IEnumerable<T>, you can call OrderBy or OrderByDescending on the results of a call to OrderBy, OrderByDescending, ThenBy or ThenByDescending. Esto presenta un nuevo orden primario que omite el orden establecido previamente.Doing this introduces a new primary ordering that ignores the previously established ordering.

Este método compara las claves mediante el comparador predeterminado Default.This method compares keys by using the default comparer Default.

Este método realiza a una ordenación estable; es decir, si las claves de dos elementos son iguales, se conserva el orden de los elementos.This method performs a stable sort; that is, if the keys of two elements are equal, the order of the elements is preserved. En cambio, una ordenación inestable no conserva el orden de los elementos que tienen la misma clave.In contrast, an unstable sort does not preserve the order of elements that have the same key.

En la sintaxis de expresión de consulta, un orderby descending (Visual C#) o Order By Descending cláusula (Visual Basic) se convierte en una invocación de OrderByDescending.In query expression syntax, an orderby descending (Visual C#) or Order By Descending (Visual Basic) clause translates to an invocation of OrderByDescending.

Consulte también:

Se aplica a