Array.FindAll(T[], Predicate<T>) Array.FindAll(T[], Predicate<T>) Array.FindAll(T[], Predicate<T>) Array.FindAll(T[], Predicate<T>) Method

定义

检索与指定谓词定义的条件匹配的所有元素。Retrieves all the elements that match the conditions defined by the specified predicate.

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

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 elements to search for.

返回

T[]

如果找到一个 Array,其中所有元素均与指定谓词定义的条件匹配,则为该数组;否则为一个空 ArrayAn Array containing all the elements that match the conditions defined by the specified predicate, if found; otherwise, an empty Array.

异常

arraynullarray is null.

-or- matchnullmatch is null.

示例

下面的示例创建一个50随机数数组,其中的值的范围介于0到1000之间。The following example creates an array of 50 random numbers with values that can range from 0 to 1,000. 然后,它使用返回值范围为300到600的 lambda 表达式调用 FindAll 方法。It then calls the FindAll method with a lambda expression that returns the values that range from 300 to 600. 请注意,lambda 表达式传递的参数名为 x; 这表示传递到 Predicate<T> 的单个数组成员。Note that the lambda expression is passed a parameter named x; this represents the individual array member that is passed to the Predicate<T>. 另请注意,可在 lambda 表达式中访问本地 @no__t 0 和 @no__t 1 变量。Also note that the local lBound and uBound variables are accessible within the lambda expression.

using System;
using System.Collections.Generic;

public class Example
{
   public static void Main()
   {
      // Get an array of n random integers.
      int[] values = GetArray(50, 0, 1000);
      int lBound = 300;
      int uBound = 600;
      int[] matchedItems = Array.FindAll(values, x =>  
                                       x >= lBound && x <= uBound);  
      for (int ctr = 0; ctr < matchedItems.Length; ctr++) {
         Console.Write("{0}  ", matchedItems[ctr]);
         if ((ctr + 1) % 12 == 0)
            Console.WriteLine();
      }
   }

   private static int[] GetArray(int n, int lower, int upper)
   {
      Random rnd = new Random();
      List<int> list = new List<int>();
      for (int ctr = 1; ctr <= n; ctr++)
         list.Add(rnd.Next(lower, upper + 1));

      return list.ToArray();
   }
}
// The example displays output similar to the following:
//       542  398  356  351  348  301  562  599  575  400  569  306
//       535  416  393  385
Imports System.Collections.Generic

Module Example
   Public Sub Main()
      ' Get an array of n random integers.
      Dim values() As Integer = GetArray(50, 0, 1000)
      Dim lBound As Integer = 300
      Dim uBound As Integer = 600
      Dim matchedItems() As Integer = Array.FindAll(values, 
                                            Function(x) x >= lBound And x <= uBound)  
      For ctr As Integer = 0 To matchedItems.Length - 1
         Console.Write("{0}  ", matchedItems(ctr))
         If (ctr + 1) Mod 12 = 0 Then Console.WriteLine()
      Next
   End Sub
   
   Private Function GetArray(n As Integer, lower As Integer, 
                             upper As Integer) As Integer()
      Dim rnd As New Random()
      Dim list As New List(Of Integer)
      For ctr As Integer = 1 To n
         list.Add(rnd.Next(lower, upper + 1))
      Next
      Return list.ToArray()
   End Function
End Module
' The example displays output similar to the following:
'       542  398  356  351  348  301  562  599  575  400  569  306
'       535  416  393  385

下面的代码示例演示 Find、@no__t 和 @no__t 泛型方法。The following code example demonstrates the Find, FindLast, and FindAll generic methods. 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".

@No__t-0 泛型方法从开始处遍历数组,并将每个元素传递到 @no__t 1 方法。The Find generic method traverses the array from the beginning, passing each element in turn to the EndsWithSaurus method. @No__t-0 方法返回元素 "Amargasaurus" 的 @no__t 为-1 时,搜索将停止。The search stops when the EndsWithSaurus method returns true for the element "Amargasaurus".

备注

在C#和 Visual Basic 中,无需显式创建 Predicate<string> 委托(Visual Basic 中的 @no__t 为2)。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.

@No__t-0 泛型方法用于从末尾向后搜索数组。The FindLast generic method is used to search the array backward from the end. 它在位置5找到元素 "Dilophosaurus"。It finds the element "Dilophosaurus" at position 5. @No__t-0 泛型方法用于返回数组,该数组包含以 "saurus" 结尾的所有元素。The FindAll generic method is used to return an array containing all the elements that end in "saurus". 显示元素。The elements are displayed.

此代码示例还演示了 @no__t 0 和 @no__t 的泛型方法。The code example also demonstrates the Exists and TrueForAll generic methods.

using namespace System;

public ref class DinoDiscoverySet
{
public:
    static void Main()
    {
        array<String^>^ dinosaurs =
        {
            "Compsognathus", "Amargasaurus", "Oviraptor",
            "Velociraptor",  "Deinonychus",  "Dilophosaurus",
            "Gallimimus",    "Triceratops"
        };

        DinoDiscoverySet^ GoMesozoic = gcnew DinoDiscoverySet(dinosaurs);

        GoMesozoic->DiscoverAll();
        GoMesozoic->DiscoverByEnding("saurus");
    }

    DinoDiscoverySet(array<String^>^ items)
    {
        dinosaurs = items;
    }

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

    void DiscoverByEnding(String^ Ending)
    {
        Predicate<String^>^ dinoType;

        if (Ending->ToLower() == "raptor")
        {
            dinoType =
                gcnew Predicate<String^>(&DinoDiscoverySet::EndsWithRaptor);
        }
        else if (Ending->ToLower() == "tops")
        {
            dinoType =
                gcnew Predicate<String^>(&DinoDiscoverySet::EndsWithTops);
        }
        else if (Ending->ToLower() == "saurus")
        {
            dinoType =
                gcnew Predicate<String^>(&DinoDiscoverySet::EndsWithSaurus);
        }
        else
        {
            dinoType =
                gcnew Predicate<String^>(&DinoDiscoverySet::EndsWithSaurus);
        }

        Console::WriteLine(
            "\nArray::Exists(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array::Exists(dinosaurs, dinoType));

        Console::WriteLine(
            "\nArray::TrueForAll(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array::TrueForAll(dinosaurs, dinoType));

        Console::WriteLine(
            "\nArray::Find(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array::Find(dinosaurs, dinoType));

        Console::WriteLine(
            "\nArray::FindLast(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array::FindLast(dinosaurs, dinoType));

        Console::WriteLine(
            "\nArray::FindAll(dinosaurs, \"{0}\"):", Ending);

        array<String^>^ subArray =
            Array::FindAll(dinosaurs, dinoType);

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

private:
    array<String^>^ dinosaurs;

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

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

    // Search predicate returns true if a string ends in "tops".
    static bool EndsWithTops(String^ s)
    {
        if ((s->Length > 3) &&
            (s->Substring(s->Length - 4)->ToLower() == "tops"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
};

int main()
{
    DinoDiscoverySet::Main();
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.Exists(dinosaurs, "saurus"): True

Array.TrueForAll(dinosaurs, "saurus"): False

Array.Find(dinosaurs, "saurus"): Amargasaurus

Array.FindLast(dinosaurs, "saurus"): Dilophosaurus

Array.FindAll(dinosaurs, "saurus"):
Amargasaurus
Dilophosaurus
*/
using System;

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

        DinoDiscoverySet GoMesozoic = new DinoDiscoverySet(dinosaurs);
        
        GoMesozoic.DiscoverAll();
        GoMesozoic.DiscoverByEnding("saurus");
    }

    private string[] dinosaurs;

    public DinoDiscoverySet(string[] items)
    {
        dinosaurs = items;
    }

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

    public void DiscoverByEnding(string Ending)
    {
        Predicate<string> dinoType;

        switch (Ending.ToLower())
        {
            case "raptor":
                dinoType = EndsWithRaptor;
                break;
            case "tops":
                dinoType = EndsWithTops;
                break;
            case "saurus":
            default:
                dinoType = EndsWithSaurus;
                break;
        }
        Console.WriteLine(
            "\nArray.Exists(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array.Exists(dinosaurs, dinoType));

        Console.WriteLine(
            "\nArray.TrueForAll(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array.TrueForAll(dinosaurs, dinoType));

        Console.WriteLine(
            "\nArray.Find(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array.Find(dinosaurs, dinoType));

        Console.WriteLine(
            "\nArray.FindLast(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array.FindLast(dinosaurs, dinoType));

        Console.WriteLine(
            "\nArray.FindAll(dinosaurs, \"{0}\"):", Ending);

        string[] subArray =
            Array.FindAll(dinosaurs, dinoType);

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

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

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

    // Search predicate returns true if a string ends in "tops".
    private bool EndsWithTops(String s)
    {
        if ((s.Length > 3) &&
            (s.Substring(s.Length - 4).ToLower() == "tops"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.Exists(dinosaurs, "saurus"): True

Array.TrueForAll(dinosaurs, "saurus"): False

Array.Find(dinosaurs, "saurus"): Amargasaurus

Array.FindLast(dinosaurs, "saurus"): Dilophosaurus

Array.FindAll(dinosaurs, "saurus"):
Amargasaurus
Dilophosaurus
*/
Public Class DinoDiscoverySet

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

        Dim GoMesozoic As New DinoDiscoverySet(dinosaurs)

        GoMesozoic.DiscoverAll()
        GoMesozoic.DiscoverByEnding("saurus")
    End Sub

    Private dinosaurs As String()

    Public Sub New(items() As String)
        dinosaurs = items
    End Sub

    Public Sub DiscoverAll()
        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next dinosaur
    End Sub

    Public Sub DiscoverByEnding(Ending As String)
        Dim dinoType As Predicate(Of String)

        Select Case Ending.ToLower()
            Case "raptor"
                dinoType = AddressOf EndsWithRaptor
            Case "tops"
                dinoType = AddressOf EndsWithTops
            Case "saurus"
                dinoType = AddressOf EndsWithSaurus
            Case Else
                dinoType = AddressOf EndsWithSaurus
        End Select

        Console.WriteLine(vbNewLine + _
            "Array.Exists(dinosaurs, ""{0}""): {1}", _
            Ending, _
            Array.Exists(dinosaurs, dinoType))

        Console.WriteLine(vbNewLine + _
            "Array.TrueForAll(dinosaurs, ""{0}""): {1}", _
            Ending, _
            Array.TrueForAll(dinosaurs, dinoType))

        Console.WriteLine(vbNewLine + _
            "Array.Find(dinosaurs, ""{0}""): {1}", _
            Ending, _
            Array.Find(dinosaurs, dinoType))

        Console.WriteLine(vbNewLine + _
            "Array.FindLast(dinosaurs, ""{0}""): {1}", _
            Ending, _
            Array.FindLast(dinosaurs, dinoType))

        Console.WriteLine(vbNewLine + _
            "Array.FindAll(dinosaurs, ""{0}""):", Ending)

        Dim subArray() As String = _
            Array.FindAll(dinosaurs, dinoType)

        For Each dinosaur As String In subArray
            Console.WriteLine(dinosaur)
        Next dinosaur
    End Sub

    ' Search predicate returns true if a string ends in "saurus".
    Private Function EndsWithSaurus(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.ToLower().EndsWith("saurus")) Then
            Return True
        Else
            Return False
        End If
    End Function

    ' Search predicate returns true if a string ends in "raptor".
    Private Function EndsWithRaptor(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.ToLower().EndsWith("raptor")) Then
            Return True
        Else
            Return False
        End If
    End Function

    ' Search predicate returns true if a string ends in "tops".
    Private Function EndsWithTops(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 > 3) AndAlso _
            (s.ToLower().EndsWith("tops")) 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.Exists(dinosaurs, "saurus"): True
'
' Array.TrueForAll(dinosaurs, "saurus"): False
'
' Array.Find(dinosaurs, "saurus"): Amargasaurus
'
' Array.FindLast(dinosaurs, "saurus"): Dilophosaurus
'
' Array.FindAll(dinosaurs, "saurus"):
' Amargasaurus
' Dilophosaurus

注解

@No__t 为方法的委托,如果传递给它的对象与委托中定义的条件相匹配,则该方法将返回 trueThe Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. @No__t 的元素分别传递到 Predicate<T>,并且与条件相匹配的元素保存在返回的数组中。The elements of array are individually passed to the Predicate<T>, and the elements that match the conditions are saved in the returned array.

此方法的运算复杂度为 O (n),其中 n 是 @no__t 的第 2 @no__t。This method is an O(n) operation, where n is the Length of array.

适用于

另请参阅