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

定義

依遞減順序,執行序列中項目的後續排序作業。Performs a subsequent ordering of the elements in a sequence in descending order.

多載

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>>)

依據索引鍵,按遞減順序執行序列中項目的後續排序作業。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>)

使用指定的比較子,依遞減順序執行序列中項目的後續排序作業。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>>)

依據索引鍵,按遞減順序執行序列中項目的後續排序作業。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)

類型參數

TSource

source 項目的類型。The type of the elements of source.

TKey

keySelector 表示之函式所傳回索引鍵的型別。The type of the key returned by the function represented by keySelector.

參數

source
IOrderedQueryable<TSource>

包含要排序之項目的 IOrderedQueryable<T>An IOrderedQueryable<T> that contains elements to sort.

keySelector
Expression<Func<TSource,TKey>>

用來從各個項目擷取索引鍵的函式。A function to extract a key from each element.

傳回

依據索引鍵按遞減順序排序其項目的 IOrderedQueryable<T>An IOrderedQueryable<T> whose elements are sorted in descending order according to a key.

例外狀況

sourcekeySelectornullsource or keySelector is null.

備註

這個方法至少有一個類型Expression<TDelegate>的參數, 其類型引數是其中一個Func<T,TResult>類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數, 您可以傳入 lambda 運算式, 它會編譯成Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

方法會產生, 其代表以ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>)結構化泛型方法的方式呼叫本身。 MethodCallExpression ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>)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. 然後, 它會MethodCallExpression將傳遞CreateQuery<TElement>(Expression)至由Provider source參數IQueryProvider的屬性所表示之的方法。It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. 呼叫CreateQuery<TElement>(Expression)的結果會轉換成類型IOrderedQueryable<T> , 並傳回。The result of calling CreateQuery<TElement>(Expression) is cast to type IOrderedQueryable<T> and returned.

因執行代表呼叫ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>)之運算式樹狀架構而產生的查詢行為, 取決於source參數類型的實作為。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. 預期的行為是, 它會根據在的source source每個專案keySelector上叫用所取得的索引鍵, 以遞減的循序執行的專案的次要排序。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. 所有先前建立的排序次序都會保留。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>)

使用指定的比較子,依遞減順序執行序列中項目的後續排序作業。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)

類型參數

TSource

source 項目的類型。The type of the elements of source.

TKey

keySelector 函式所傳回索引鍵的型別。The type of the key that is returned by the keySelector function.

參數

source
IOrderedQueryable<TSource>

包含要排序之項目的 IOrderedQueryable<T>An IOrderedQueryable<T> that contains elements to sort.

keySelector
Expression<Func<TSource,TKey>>

用來從各個項目擷取索引鍵的函式。A function to extract a key from each element.

comparer
IComparer<TKey>

用來比較金鑰的 IComparer<T>An IComparer<T> to compare keys.

傳回

依據索引鍵按遞減順序排序其項目的集合。A collection whose elements are sorted in descending order according to a key.

例外狀況

sourcekeySelectorcomparernullsource or keySelector or comparer is null.

範例

下列程式碼範例示範如何使用ThenByDescending<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) , 以使用自訂比較子, 依遞減循序執行序列中專案的次要排序。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

備註

這個方法至少有一個類型Expression<TDelegate>的參數, 其類型引數是其中一個Func<T,TResult>類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數, 您可以傳入 lambda 運算式, 它會編譯成Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

方法會產生, 其代表以ThenBy<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)結構化泛型方法的方式呼叫本身。 MethodCallExpression ThenBy<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)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. 然後, 它會MethodCallExpression將傳遞CreateQuery<TElement>(Expression)至由Provider source參數IQueryProvider的屬性所表示之的方法。It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. 呼叫CreateQuery<TElement>(Expression)的結果會轉換成類型IOrderedQueryable<T> , 並傳回。The result of calling CreateQuery<TElement>(Expression) is cast to type IOrderedQueryable<T> and returned.

因執行代表呼叫ThenBy<TSource,TKey>(IOrderedQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)之運算式樹狀架構而產生的查詢行為, 取決於source參數類型的實作為。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. 預期的行為是, 它會根據在的source source每個專案keySelector上叫用所取得的索引鍵, 以遞減的循序執行的專案的次要排序。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. 所有先前建立的排序次序都會保留。All previously established sort orders are preserved. comparer參數是用來比較索引鍵值。The comparer parameter is used to compare key values.

適用於