Array.FindLastIndex Array.FindLastIndex Array.FindLastIndex Array.FindLastIndex Method

定义

搜索与指定谓词定义的条件匹配的元素,然后返回 Array 或其某个部分中最后一个匹配项的从零开始的索引。Searches for an element that matches the conditions defined by a specified predicate, and returns the zero-based index of the last occurrence within an Array or a portion of it.

重载

FindLastIndex<T>(T[], Predicate<T>) FindLastIndex<T>(T[], Predicate<T>) FindLastIndex<T>(T[], Predicate<T>) FindLastIndex<T>(T[], Predicate<T>)

搜索与指定谓词所定义的条件相匹配的元素,并返回整个 Array 中最后一个匹配元素的从零开始的索引。Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the entire Array.

FindLastIndex<T>(T[], Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Predicate<T>)

搜索与由指定谓词定义的条件相匹配的元素,并返回 Array 中从第一个元素到指定索引的元素范围内最后一个匹配项的从零开始的索引。Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the Array that extends from the first element to the specified index.

FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Int32, Predicate<T>)

搜索与指定谓词所定义的条件相匹配的元素,并返回 Array 中包含指定元素个数、到指定索引结束的元素范围内最后一个匹配项的从零开始的索引。Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the Array that contains the specified number of elements and ends at the specified index.

FindLastIndex<T>(T[], Predicate<T>) FindLastIndex<T>(T[], Predicate<T>) FindLastIndex<T>(T[], Predicate<T>) FindLastIndex<T>(T[], Predicate<T>)

搜索与指定谓词所定义的条件相匹配的元素,并返回整个 Array 中最后一个匹配元素的从零开始的索引。Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the entire Array.

public:
generic <typename T>
 static int FindLastIndex(cli::array <T> ^ array, Predicate<T> ^ match);
public static int FindLastIndex<T> (T[] array, Predicate<T> match);
static member FindLastIndex : 'T[] * Predicate<'T> -> int
Public Shared Function FindLastIndex(Of T) (array As T(), match As Predicate(Of T)) As Integer

类型参数

T

数组元素的类型。The type of the elements of the array.

参数

array
T[]

要搜索的从零开始的一维 ArrayThe one-dimensional, zero-based Array to search.

match
Predicate<T> Predicate<T> Predicate<T> Predicate<T>

Predicate<T>,定义要搜索元素的条件。The Predicate<T> that defines the conditions of the element to search for.

返回

如果找到与 match 定义的条件相匹配的最后一个元素,则为该元素的从零开始的索引;否则为 -1。The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

异常

arraynullarray is null.

-or- matchnullmatch is null.

示例

下面的代码示例演示FindLastIndex泛型方法的所有三个重载。The following code example demonstrates all three overloads of the FindLastIndex generic method. 创建一个字符串数组, 其中包含8个恐龙名称, 其中两个名称 (位置1和 5) 以 "saurus" 结尾。An array of strings is created, containing 8 dinosaur names, two of which (at positions 1 and 5) end with "saurus". 此代码示例还定义了一个名为EndsWithSaurus的搜索谓词方法, 该方法接受一个字符串参数, 并返回一个布尔值, 指示输入字符串是否以 "saurus" 结尾。The code example also defines a search predicate method named EndsWithSaurus, which accepts a string parameter and returns a Boolean value indicating whether the input string ends in "saurus".

方法重载从末尾开始向后遍历数组, 并将每个元素传递EndsWithSaurus给方法。 FindLastIndex<T>(T[], Predicate<T>)The FindLastIndex<T>(T[], Predicate<T>) method overload traverses the array backward from the end, passing each element in turn to the EndsWithSaurus method. EndsWithSaurus方法为位置5的元素true返回时, 搜索将停止。The search stops when the EndsWithSaurus method returns true for the element at position 5.

备注

在C#和 Visual Basic 中, 无需显式创建Predicate<string>委托 (Predicate(Of String)在 Visual Basic 中)。In C# and Visual Basic, it is not necessary to create the Predicate<string> delegate (Predicate(Of String) in Visual Basic) explicitly. 这些语言从上下文推断正确的委托并自动创建它。These languages infer the correct delegate from context and create it automatically.

FindLastIndex<T>(T[], Int32, Predicate<T>)方法重载用于从位置4开始搜索数组, 并向后移动到数组的开头。The FindLastIndex<T>(T[], Int32, Predicate<T>) method overload is used to search the array beginning at position 4 and continuing backward to the beginning of the array. 它在位置1找到元素。It finds the element at position 1. 最后, FindLastIndex<T>(T[], Int32, Int32, Predicate<T>)使用方法重载搜索从位置4开始的三个元素的范围并向后 (即元素4、3和 2)。Finally, the FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) method overload is used to search the range of three elements beginning at position 4 and working backward (that is, elements 4, 3, and 2). 它将返回-1, 因为该范围中没有以 "saurus" 结尾的恐龙名称。It returns -1 because there are no dinosaur names in that range that end with "saurus".

using namespace System;

// Search predicate returns true if a string ends in "saurus".
bool EndsWithSaurus(String^ s)
{
    if ((s->Length > 5) && 
        (s->Substring(s->Length - 6)->ToLower() == "saurus"))
    {
        return true;
    }
    else
    {
        return false;
    }
};

void main()
{
    array<String^>^ dinosaurs = { "Compsognathus", 
        "Amargasaurus",   "Oviraptor",      "Velociraptor", 
        "Deinonychus",    "Dilophosaurus",  "Gallimimus", 
        "Triceratops" };

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, EndsWithSaurus): {0}", 
        Array::FindLastIndex(dinosaurs, gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, 4, EndsWithSaurus): {0}",
        Array::FindLastIndex(dinosaurs, 4, gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): {0}",
        Array::FindLastIndex(dinosaurs, 4, 3, gcnew Predicate<String^>(EndsWithSaurus)));
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array::FindLastIndex(dinosaurs, EndsWithSaurus): 5

Array::FindLastIndex(dinosaurs, 4, EndsWithSaurus): 1

Array::FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): -1
 */
using System;

public class Example
{
    public static void Main()
    {
        string[] dinosaurs = { "Compsognathus", 
            "Amargasaurus",   "Oviraptor",      "Velociraptor", 
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", 
            "Triceratops" };

        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, EndsWithSaurus): {0}", 
            Array.FindLastIndex(dinosaurs, EndsWithSaurus));

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, 4, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus));

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus));
    }

    // Search predicate returns true if a string ends in "saurus".
    private static bool EndsWithSaurus(String s)
    {
        if ((s.Length > 5) && 
            (s.Substring(s.Length - 6).ToLower() == "saurus"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.FindLastIndex(dinosaurs, EndsWithSaurus): 5

Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus): 1

Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): -1
 */
Imports System

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs() As String = { "Compsognathus", _
            "Amargasaurus",   "Oviraptor",      "Velociraptor", _
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", _
            "Triceratops" }

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus))

    End Sub

    ' Search predicate returns true if a string ends in "saurus".
    Private Shared Function EndsWithSaurus(ByVal s As String) _
        As Boolean

        ' AndAlso prevents evaluation of the second Boolean
        ' expression if the string is so short that an error
        ' would occur.
        If (s.Length > 5) AndAlso _
            (s.Substring(s.Length - 6).ToLower() = "saurus") Then
            Return True
        Else
            Return False
        End If
    End Function
End Class

' This code example produces the following output:
'
'Compsognathus
'Amargasaurus
'Oviraptor
'Velociraptor
'Deinonychus
'Dilophosaurus
'Gallimimus
'Triceratops
'
'Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus): 5
'
'Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus): 1
'
'Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus): -1

注解

Array向后搜索从最后一个元素开始, 到第一个元素结束。The Array is searched backward starting at the last element and ending at the first element.

是一个方法委托, 如果传递给它的对象与委托中定义的条件相匹配, 则它将返回truePredicate<T>The Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. 的元素array分别传递Predicate<T>到。The elements of array are individually passed to the Predicate<T>.

此方法为 On() 运算, 其中nLengtharrayThis method is an O(n) operation, where n is the Length of array.

另请参阅

FindLastIndex<T>(T[], Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Predicate<T>)

搜索与由指定谓词定义的条件相匹配的元素,并返回 Array 中从第一个元素到指定索引的元素范围内最后一个匹配项的从零开始的索引。Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the Array that extends from the first element to the specified index.

public:
generic <typename T>
 static int FindLastIndex(cli::array <T> ^ array, int startIndex, Predicate<T> ^ match);
public static int FindLastIndex<T> (T[] array, int startIndex, Predicate<T> match);
static member FindLastIndex : 'T[] * int * Predicate<'T> -> int
Public Shared Function FindLastIndex(Of T) (array As T(), startIndex As Integer, match As Predicate(Of T)) As Integer

类型参数

T

数组元素的类型。The type of the elements of the array.

参数

array
T[]

要搜索的从零开始的一维 ArrayThe one-dimensional, zero-based Array to search.

startIndex
Int32 Int32 Int32 Int32

向后搜索的从零开始的起始索引。The zero-based starting index of the backward search.

match
Predicate<T> Predicate<T> Predicate<T> Predicate<T>

Predicate<T>,定义要搜索元素的条件。The Predicate<T> that defines the conditions of the element to search for.

返回

如果找到与 match 定义的条件相匹配的最后一个元素,则为该元素的从零开始的索引;否则为 -1。The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

异常

arraynullarray is null.

- 或 --or- matchnullmatch is null.

startIndex 超出了 array 的有效索引范围。startIndex is outside the range of valid indexes for array.

示例

下面的代码示例演示FindLastIndex泛型方法的所有三个重载。The following code example demonstrates all three overloads of the FindLastIndex generic method. 创建一个字符串数组, 其中包含8个恐龙名称, 其中两个名称 (位置1和 5) 以 "saurus" 结尾。An array of strings is created, containing 8 dinosaur names, two of which (at positions 1 and 5) end with "saurus". 此代码示例还定义了一个名为EndsWithSaurus的搜索谓词方法, 该方法接受一个字符串参数, 并返回一个布尔值, 指示输入字符串是否以 "saurus" 结尾。The code example also defines a search predicate method named EndsWithSaurus, which accepts a string parameter and returns a Boolean value indicating whether the input string ends in "saurus".

方法重载从末尾开始向后遍历数组, 并将每个元素传递EndsWithSaurus给方法。 FindLastIndex<T>(T[], Predicate<T>)The FindLastIndex<T>(T[], Predicate<T>) method overload traverses the array backward from the end, passing each element in turn to the EndsWithSaurus method. EndsWithSaurus方法为位置5的元素true返回时, 搜索将停止。The search stops when the EndsWithSaurus method returns true for the element at position 5.

备注

在C#和 Visual Basic 中, 无需显式创建Predicate<string>委托 (Predicate(Of String)在 Visual Basic 中)。In C# and Visual Basic, it is not necessary to create the Predicate<string> delegate (Predicate(Of String) in Visual Basic) explicitly. 这些语言从上下文推断正确的委托并自动创建它。These languages infer the correct delegate from context and create it automatically.

FindLastIndex<T>(T[], Int32, Predicate<T>)方法重载用于从位置4开始搜索数组, 并向后移动到数组的开头。The FindLastIndex<T>(T[], Int32, Predicate<T>) method overload is used to search the array beginning at position 4 and continuing backward to the beginning of the array. 它在位置1找到元素。It finds the element at position 1. 最后, FindLastIndex<T>(T[], Int32, Int32, Predicate<T>)使用方法重载搜索从位置4开始的三个元素的范围并向后 (即元素4、3和 2)。Finally, the FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) method overload is used to search the range of three elements beginning at position 4 and working backward (that is, elements 4, 3, and 2). 它将返回-1, 因为该范围中没有以 "saurus" 结尾的恐龙名称。It returns -1 because there are no dinosaur names in that range that end with "saurus".

using namespace System;

// Search predicate returns true if a string ends in "saurus".
bool EndsWithSaurus(String^ s)
{
    if ((s->Length > 5) && 
        (s->Substring(s->Length - 6)->ToLower() == "saurus"))
    {
        return true;
    }
    else
    {
        return false;
    }
};

void main()
{
    array<String^>^ dinosaurs = { "Compsognathus", 
        "Amargasaurus",   "Oviraptor",      "Velociraptor", 
        "Deinonychus",    "Dilophosaurus",  "Gallimimus", 
        "Triceratops" };

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, EndsWithSaurus): {0}", 
        Array::FindLastIndex(dinosaurs, gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, 4, EndsWithSaurus): {0}",
        Array::FindLastIndex(dinosaurs, 4, gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): {0}",
        Array::FindLastIndex(dinosaurs, 4, 3, gcnew Predicate<String^>(EndsWithSaurus)));
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array::FindLastIndex(dinosaurs, EndsWithSaurus): 5

Array::FindLastIndex(dinosaurs, 4, EndsWithSaurus): 1

Array::FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): -1
 */
using System;

public class Example
{
    public static void Main()
    {
        string[] dinosaurs = { "Compsognathus", 
            "Amargasaurus",   "Oviraptor",      "Velociraptor", 
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", 
            "Triceratops" };

        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, EndsWithSaurus): {0}", 
            Array.FindLastIndex(dinosaurs, EndsWithSaurus));

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, 4, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus));

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus));
    }

    // Search predicate returns true if a string ends in "saurus".
    private static bool EndsWithSaurus(String s)
    {
        if ((s.Length > 5) && 
            (s.Substring(s.Length - 6).ToLower() == "saurus"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.FindLastIndex(dinosaurs, EndsWithSaurus): 5

Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus): 1

Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): -1
 */
Imports System

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs() As String = { "Compsognathus", _
            "Amargasaurus",   "Oviraptor",      "Velociraptor", _
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", _
            "Triceratops" }

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus))

    End Sub

    ' Search predicate returns true if a string ends in "saurus".
    Private Shared Function EndsWithSaurus(ByVal s As String) _
        As Boolean

        ' AndAlso prevents evaluation of the second Boolean
        ' expression if the string is so short that an error
        ' would occur.
        If (s.Length > 5) AndAlso _
            (s.Substring(s.Length - 6).ToLower() = "saurus") Then
            Return True
        Else
            Return False
        End If
    End Function
End Class

' This code example produces the following output:
'
'Compsognathus
'Amargasaurus
'Oviraptor
'Velociraptor
'Deinonychus
'Dilophosaurus
'Gallimimus
'Triceratops
'
'Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus): 5
'
'Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus): 1
'
'Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus): -1

注解

Array后搜索startIndex从第一个元素开始和结束的位置。The Array is searched backward starting at startIndex and ending at the first element.

是一个方法委托, 如果传递给它的对象与委托中定义的条件相匹配, 则它将返回truePredicate<T>The Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. 的元素array分别传递Predicate<T>到。The elements of array are individually passed to the Predicate<T>.

此方法为 On() 运算, 其中n是从开始arraystartIndex的元素的数目。This method is an O(n) operation, where n is the number of elements from the beginning of array to startIndex.

另请参阅

FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) FindLastIndex<T>(T[], Int32, Int32, Predicate<T>)

搜索与指定谓词所定义的条件相匹配的元素,并返回 Array 中包含指定元素个数、到指定索引结束的元素范围内最后一个匹配项的从零开始的索引。Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the Array that contains the specified number of elements and ends at the specified index.

public:
generic <typename T>
 static int FindLastIndex(cli::array <T> ^ array, int startIndex, int count, Predicate<T> ^ match);
public static int FindLastIndex<T> (T[] array, int startIndex, int count, Predicate<T> match);
static member FindLastIndex : 'T[] * int * int * Predicate<'T> -> int
Public Shared Function FindLastIndex(Of T) (array As T(), startIndex As Integer, count As Integer, match As Predicate(Of T)) As Integer

类型参数

T

数组元素的类型。The type of the elements of the array.

参数

array
T[]

要搜索的从零开始的一维 ArrayThe one-dimensional, zero-based Array to search.

startIndex
Int32 Int32 Int32 Int32

向后搜索的从零开始的起始索引。The zero-based starting index of the backward search.

count
Int32 Int32 Int32 Int32

要搜索的部分中的元素数。The number of elements in the section to search.

match
Predicate<T> Predicate<T> Predicate<T> Predicate<T>

Predicate<T>,定义要搜索元素的条件。The Predicate<T> that defines the conditions of the element to search for.

返回

如果找到与 match 定义的条件相匹配的最后一个元素,则为该元素的从零开始的索引;否则为 -1。The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

异常

arraynullarray is null.

-or- matchnullmatch is null.

startIndex 超出了 array 的有效索引范围。startIndex is outside the range of valid indexes for array.

- 或 --or- count 小于零。count is less than zero.

-or- startIndexcount 未在 array 中指定有效部分。startIndex and count do not specify a valid section in array.

示例

下面的代码示例演示FindLastIndex泛型方法的所有三个重载。The following code example demonstrates all three overloads of the FindLastIndex generic method. 创建一个字符串数组, 其中包含8个恐龙名称, 其中两个名称 (位置1和 5) 以 "saurus" 结尾。An array of strings is created, containing 8 dinosaur names, two of which (at positions 1 and 5) end with "saurus". 此代码示例还定义了一个名为EndsWithSaurus的搜索谓词方法, 该方法接受一个字符串参数, 并返回一个布尔值, 指示输入字符串是否以 "saurus" 结尾。The code example also defines a search predicate method named EndsWithSaurus, which accepts a string parameter and returns a Boolean value indicating whether the input string ends in "saurus".

方法重载从末尾开始向后遍历数组, 并将每个元素传递EndsWithSaurus给方法。 FindLastIndex<T>(T[], Predicate<T>)The FindLastIndex<T>(T[], Predicate<T>) method overload traverses the array backward from the end, passing each element in turn to the EndsWithSaurus method. EndsWithSaurus方法为位置5的元素true返回时, 搜索将停止。The search stops when the EndsWithSaurus method returns true for the element at position 5.

备注

在C#和 Visual Basic 中, 无需显式创建Predicate<string>委托 (Predicate(Of String)在 Visual Basic 中)。In C# and Visual Basic, it is not necessary to create the Predicate<string> delegate (Predicate(Of String) in Visual Basic) explicitly. 这些语言从上下文推断正确的委托并自动创建它。These languages infer the correct delegate from context and create it automatically.

FindLastIndex<T>(T[], Int32, Predicate<T>)方法重载用于从位置4开始搜索数组, 并向后移动到数组的开头。The FindLastIndex<T>(T[], Int32, Predicate<T>) method overload is used to search the array beginning at position 4 and continuing backward to the beginning of the array. 它在位置1找到元素。It finds the element at position 1. 最后, FindLastIndex<T>(T[], Int32, Int32, Predicate<T>)使用方法重载搜索从位置4开始的三个元素的范围并向后 (即元素4、3和 2)。Finally, the FindLastIndex<T>(T[], Int32, Int32, Predicate<T>) method overload is used to search the range of three elements beginning at position 4 and working backward (that is, elements 4, 3, and 2). 它将返回-1, 因为该范围中没有以 "saurus" 结尾的恐龙名称。It returns -1 because there are no dinosaur names in that range that end with "saurus".

using namespace System;

// Search predicate returns true if a string ends in "saurus".
bool EndsWithSaurus(String^ s)
{
    if ((s->Length > 5) && 
        (s->Substring(s->Length - 6)->ToLower() == "saurus"))
    {
        return true;
    }
    else
    {
        return false;
    }
};

void main()
{
    array<String^>^ dinosaurs = { "Compsognathus", 
        "Amargasaurus",   "Oviraptor",      "Velociraptor", 
        "Deinonychus",    "Dilophosaurus",  "Gallimimus", 
        "Triceratops" };

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, EndsWithSaurus): {0}", 
        Array::FindLastIndex(dinosaurs, gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, 4, EndsWithSaurus): {0}",
        Array::FindLastIndex(dinosaurs, 4, gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nArray::FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): {0}",
        Array::FindLastIndex(dinosaurs, 4, 3, gcnew Predicate<String^>(EndsWithSaurus)));
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array::FindLastIndex(dinosaurs, EndsWithSaurus): 5

Array::FindLastIndex(dinosaurs, 4, EndsWithSaurus): 1

Array::FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): -1
 */
using System;

public class Example
{
    public static void Main()
    {
        string[] dinosaurs = { "Compsognathus", 
            "Amargasaurus",   "Oviraptor",      "Velociraptor", 
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", 
            "Triceratops" };

        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, EndsWithSaurus): {0}", 
            Array.FindLastIndex(dinosaurs, EndsWithSaurus));

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, 4, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus));

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus));
    }

    // Search predicate returns true if a string ends in "saurus".
    private static bool EndsWithSaurus(String s)
    {
        if ((s.Length > 5) && 
            (s.Substring(s.Length - 6).ToLower() == "saurus"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.FindLastIndex(dinosaurs, EndsWithSaurus): 5

Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus): 1

Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): -1
 */
Imports System

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs() As String = { "Compsognathus", _
            "Amargasaurus",   "Oviraptor",      "Velociraptor", _
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", _
            "Triceratops" }

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus))

    End Sub

    ' Search predicate returns true if a string ends in "saurus".
    Private Shared Function EndsWithSaurus(ByVal s As String) _
        As Boolean

        ' AndAlso prevents evaluation of the second Boolean
        ' expression if the string is so short that an error
        ' would occur.
        If (s.Length > 5) AndAlso _
            (s.Substring(s.Length - 6).ToLower() = "saurus") Then
            Return True
        Else
            Return False
        End If
    End Function
End Class

' This code example produces the following output:
'
'Compsognathus
'Amargasaurus
'Oviraptor
'Velociraptor
'Deinonychus
'Dilophosaurus
'Gallimimus
'Triceratops
'
'Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus): 5
'
'Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus): 1
'
'Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus): -1

注解

startIndex startIndex count如果Array 大于0,则搜索从开始,到从减号+1开始向后终止。countThe Array is searched backward starting at startIndex and ending at startIndex minus count plus 1, if count is greater than 0.

是一个方法委托, 如果传递给它的对象与委托中定义的条件相匹配, 则它将返回truePredicate<T>The Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. 的元素array分别传递Predicate<T>到。The elements of array are individually passed to the Predicate<T>.

此方法是 O (n) 运算, 其中ncountThis method is an O(n) operation, where n is count.

另请参阅

适用于