Queryable.ThenByDescending Queryable.ThenByDescending Queryable.ThenByDescending Queryable.ThenByDescending Method

Definizione

Esegue un successivo ordinamento in senso decrescente degli elementi di una sequenza.Performs a subsequent ordering of the elements in a sequence in descending order.

Overload

ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>)

Esegue un successivo ordinamento in senso decrescente in base a una chiave degli elementi di una sequenza.Performs a subsequent ordering of the elements in a sequence in descending order, according to a key.

ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)

Esegue un ordinamento secondario in senso decrescente degli elementi di una sequenza utilizzando un operatore di confronto specificato.Performs a subsequent ordering of the elements in a sequence in descending order by using a specified comparer.

ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>)

Esegue un successivo ordinamento in senso decrescente in base a una chiave degli elementi di una sequenza.Performs a subsequent ordering of the elements in a sequence in descending order, according to a key.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IOrderedQueryable<TSource> ^ ThenByDescending(System::Linq::IOrderedQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector);
public static System.Linq.IOrderedQueryable<TSource> ThenByDescending<TSource,TKey> (this System.Linq.IOrderedQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector);
static member ThenByDescending : System.Linq.IOrderedQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> -> System.Linq.IOrderedQueryable<'Source>
<Extension()>
Public Function ThenByDescending(Of TSource, TKey) (source As IOrderedQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey))) As IOrderedQueryable(Of TSource)

Parametri di tipo

TSource

Tipo degli elementi di source.The type of the elements of source.

TKey

Tipo della chiave restituita dalla funzione rappresentata dall'oggetto keySelector.The type of the key returned by the function represented by keySelector.

Parametri

source
IOrderedQueryable<TSource>

Oggetto IOrderedQueryable<T> che contiene gli elementi da ordinare.An IOrderedQueryable<T> that contains elements to sort.

keySelector
Expression<Func<TSource,TKey>>

Funzione per estrarre una chiave da ogni elemento.A function to extract a key from each element.

Restituisce

Oggetto IOrderedQueryable<T> i cui elementi vengono ordinati in senso decrescente in base a una chiave.An IOrderedQueryable<T> whose elements are sorted in descending order according to a key.

Eccezioni

source o keySelector è null.source or keySelector is null.

Commenti

Questo metodo ha almeno un parametro di tipo Expression<TDelegate> il Func<T,TResult> cui argomento di tipo è uno dei tipi.This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. Per questi parametri, è possibile passare un'espressione lambda che verrà compilata in un oggetto Expression<TDelegate>.For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Il ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) metodo genera un MethodCallExpression oggetto che rappresenta ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) la chiamata a se stesso come metodo generico costruito.The ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) method generates a MethodCallExpression that represents calling ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) itself as a constructed generic method. Passa MethodCallExpression IQueryProvider quindi al source metodo dell'oggetto rappresentato dalla proprietàdelparametro.Provider CreateQuery<TElement>(Expression)It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. Il risultato della chiamata CreateQuery<TElement>(Expression) a viene eseguito il IOrderedQueryable<T> cast al tipo e restituito.The result of calling CreateQuery<TElement>(Expression) is cast to type IOrderedQueryable<T> and returned.

Il comportamento della query che si verifica in seguito all'esecuzione di un albero delle espressioni che ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) rappresenta la chiamata dipende dall'implementazione del tipo source di parametro.The query behavior that occurs as a result of executing an expression tree that represents calling ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>) depends on the implementation of the type of the source parameter. Il comportamento previsto è che esegue un ordinamento secondario degli elementi di source in ordine decrescente, in base alla chiave ottenuta keySelector richiamando su ogni elemento di source.The expected behavior is that it performs a secondary sort of the elements of source in descending order, based on the key obtained by invoking keySelector on each element of source. Vengono conservati tutti gli ordinamenti precedentemente stabiliti.All previously established sort orders are preserved.

ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)

Esegue un ordinamento secondario in senso decrescente degli elementi di una sequenza utilizzando un operatore di confronto specificato.Performs a subsequent ordering of the elements in a sequence in descending order by using a specified comparer.

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

Parametri di tipo

TSource

Tipo degli elementi di source.The type of the elements of source.

TKey

Tipo della chiave restituita dalla funzione keySelector.The type of the key that is returned by the keySelector function.

Parametri

source
IOrderedQueryable<TSource>

Oggetto IOrderedQueryable<T> che contiene gli elementi da ordinare.An IOrderedQueryable<T> that contains elements to sort.

keySelector
Expression<Func<TSource,TKey>>

Funzione per estrarre una chiave da ogni elemento.A function to extract a key from each element.

comparer
IComparer<TKey>

Oggetto IComparer<T> per confrontare le chiavi.An IComparer<T> to compare keys.

Restituisce

Raccolta i cui elementi vengono disposti in ordine decrescente in base a una chiave.A collection whose elements are sorted in descending order according to a key.

Eccezioni

Il parametro source, il parametro keySelector o il parametro comparer è null.source or keySelector or comparer is null.

Esempi

Nell'esempio di codice riportato di seguito viene ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) illustrato come utilizzare per eseguire un ordinamento secondario degli elementi di una sequenza in ordine decrescente utilizzando un operatore di confronto personalizzato.The following code example demonstrates how to use ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) to perform a secondary ordering of the elements in a sequence in descending order by using a custom comparer.

public class CaseInsensitiveComparer : IComparer<string>
{
    public int Compare(string x, string y)
    {
        return string.Compare(x, y, true);
    }
}

public static void ThenByDescendingEx1()
{
    string[] fruits = 
    { "apPLe", "baNanA", "apple", "APple", "orange", "BAnana", "ORANGE", "apPLE" };

    // Sort the strings first ascending by their length and 
    // then descending using a custom case insensitive comparer.
    IEnumerable<string> query =
        fruits.AsQueryable()
        .OrderBy(fruit => fruit.Length)
        .ThenByDescending(fruit => fruit, new CaseInsensitiveComparer());

    foreach (string fruit in query)
        Console.WriteLine(fruit);
}

/*
    This code produces the following output:

    apPLe
    apple
    APple
    apPLE
    orange
    ORANGE
    baNanA
    BAnana
*/

Class CaseInsensitiveComparer
    Implements IComparer(Of String)

    Function Compare(ByVal x As String, ByVal y As String) As Integer _
        Implements IComparer(Of String).Compare

        ' Compare values and ignore case.
        Return String.Compare(x, y, True)
    End Function
End Class

Sub ThenByDescendingEx1()
    Dim fruits() As String = _
        {"apPLe", "baNanA", "apple", "APple", "orange", "BAnana", "ORANGE", "apPLE"}

    ' Sort the strings first ascending by their length and 
    ' then descending by using a custom case insensitive comparer.
    Dim query = fruits.AsQueryable() _
        .OrderBy(Function(fruit) fruit.Length) _
        .ThenByDescending(Function(fruit) fruit, New CaseInsensitiveComparer())

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

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

' This code produces the following output:

' apPLe
' apple
' APple
' apPLE
' orange
' ORANGE
' baNanA
' BAnana

Commenti

Questo metodo ha almeno un parametro di tipo Expression<TDelegate> il Func<T,TResult> cui argomento di tipo è uno dei tipi.This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. Per questi parametri, è possibile passare un'espressione lambda che verrà compilata in un oggetto Expression<TDelegate>.For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Il ThenBy<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) metodo genera un MethodCallExpression oggetto che rappresenta ThenBy<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) la chiamata a se stesso come metodo generico costruito.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. Passa MethodCallExpression IQueryProvider quindi al source metodo dell'oggetto rappresentato dalla proprietàdelparametro.Provider CreateQuery<TElement>(Expression)It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. Il risultato della chiamata CreateQuery<TElement>(Expression) a viene eseguito il IOrderedQueryable<T> cast al tipo e restituito.The result of calling CreateQuery<TElement>(Expression) is cast to type IOrderedQueryable<T> and returned.

Il comportamento della query che si verifica in seguito all'esecuzione di un albero delle espressioni che ThenBy<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) rappresenta la chiamata dipende dall'implementazione del tipo source di parametro.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. Il comportamento previsto è che esegue un ordinamento secondario degli elementi di source in ordine decrescente, in base alla chiave ottenuta keySelector richiamando su ogni elemento di source.The expected behavior is that it performs a secondary sort of the elements of source in descending order, based on the key obtained by invoking keySelector on each element of source. Vengono conservati tutti gli ordinamenti precedentemente stabiliti.All previously established sort orders are preserved. Il comparer parametro viene utilizzato per confrontare i valori di chiave.The comparer parameter is used to compare key values.

Si applica a