Queryable.OrderByDescending 메서드

정의

시퀀스의 요소를 내림차순으로 정렬합니다.Sorts the elements of a sequence in descending order.

오버로드

OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)

시퀀스의 요소를 키에 따라 내림차순으로 정렬합니다.Sorts the elements of a sequence in descending order according to a key.

OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)

지정된 비교자를 사용하여 시퀀스의 요소를 내림차순으로 정렬합니다.Sorts the elements of a sequence in descending order by using a specified comparer.

OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)

시퀀스의 요소를 키에 따라 내림차순으로 정렬합니다.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::IOrderedQueryable<TSource> ^ OrderByDescending(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector);
public static System.Linq.IOrderedQueryable<TSource> OrderByDescending<TSource,TKey> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector);
static member OrderByDescending : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> -> System.Linq.IOrderedQueryable<'Source>
<Extension()>
Public Function OrderByDescending(Of TSource, TKey) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey))) As IOrderedQueryable(Of TSource)

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function that is represented by keySelector.

매개 변수

source
IQueryable<TSource>

정렬할 값의 시퀀스입니다.A sequence of values to order.

keySelector
Expression<Func<TSource,TKey>>

요소에서 키를 추출하는 함수입니다.A function to extract a key from an element.

반환

IOrderedQueryable<TSource>

요소가 키에 따라 내림차순으로 정렬된 IOrderedQueryable<T>입니다.An IOrderedQueryable<T> whose elements are sorted in descending order according to a key.

예외

source 또는 keySelectornull인 경우source or keySelector is null.

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) .The OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) method generates a MethodCallExpression that represents calling OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. 호출 결과는 CreateQuery<TElement>(Expression) 형식으로 캐스팅 되 IOrderedQueryable<T> 고 반환 됩니다.The result of calling CreateQuery<TElement>(Expression) is cast to type IOrderedQueryable<T> and returned.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source keySelector 의 각 요소에 대해를 호출 하 여 가져온 키를 기준으로의 요소를 내림차순으로 정렬 하는 것입니다 source .The expected behavior is that it sorts the elements of source in descending order, based on the key obtained by invoking keySelector on each element of source.

적용 대상

OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)

지정된 비교자를 사용하여 시퀀스의 요소를 내림차순으로 정렬합니다.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::IOrderedQueryable<TSource> ^ OrderByDescending(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector, System::Collections::Generic::IComparer<TKey> ^ comparer);
public static System.Linq.IOrderedQueryable<TSource> OrderByDescending<TSource,TKey> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Collections.Generic.IComparer<TKey> comparer);
public static System.Linq.IOrderedQueryable<TSource> OrderByDescending<TSource,TKey> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Collections.Generic.IComparer<TKey>? comparer);
static member OrderByDescending : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> * System.Collections.Generic.IComparer<'Key> -> System.Linq.IOrderedQueryable<'Source>
<Extension()>
Public Function OrderByDescending(Of TSource, TKey) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), comparer As IComparer(Of TKey)) As IOrderedQueryable(Of TSource)

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function that is represented by keySelector.

매개 변수

source
IQueryable<TSource>

정렬할 값의 시퀀스입니다.A sequence of values to order.

keySelector
Expression<Func<TSource,TKey>>

요소에서 키를 추출하는 함수입니다.A function to extract a key from an element.

comparer
IComparer<TKey>

키를 비교할 IComparer<T>입니다.An IComparer<T> to compare keys.

반환

IOrderedQueryable<TSource>

요소가 키에 따라 내림차순으로 정렬된 IOrderedQueryable<T>입니다.An IOrderedQueryable<T> whose elements are sorted in descending order according to a key.

예외

source, keySelector 또는 comparernull인 경우source or keySelector or comparer is null.

예제

다음 코드 예제에서는 OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) 사용자 지정 비교자를 사용 하 여 시퀀스의 요소를 내림차순으로 정렬 하는 방법을 보여 줍니다.The following code example demonstrates how to use OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) to sort the elements of a sequence in descending order by using 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 };

    // Sort the decimal values in descending order
    // by using a custom comparer.
    IEnumerable<decimal> query =
        decimals.AsQueryable()
        .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
*/

''' <summary>
''' This class provides a custom implementation of the
''' IComparer.Compare() method. It sorts by the fractional part of the decimal number.
''' </summary>
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.AsQueryable(). _
        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

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) .The OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) method generates a MethodCallExpression that represents calling OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter. 호출 결과는 CreateQuery<TElement>(Expression) 형식으로 캐스팅 되 IOrderedQueryable<T> 고 반환 됩니다.The result of calling CreateQuery<TElement>(Expression) is cast to type IOrderedQueryable<T> and returned.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling OrderByDescending<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IComparer<TKey>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source keySelector 의 각 요소에 대해를 호출 하 여 가져온 키를 기준으로의 요소를 내림차순으로 정렬 하는 것입니다 source .The expected behavior is that it sorts the elements of source in descending order, based on the key obtained by invoking keySelector on each element of source. comparer매개 변수는 키를 비교 하는 데 사용 됩니다.The comparer parameter is used to compare keys.

적용 대상