List<T>.RemoveAll(Predicate<T>) 方法

定义

移除与指定的谓词所定义的条件相匹配的所有元素。Removes all the elements that match the conditions defined by the specified predicate.

public:
 int RemoveAll(Predicate<T> ^ match);
public int RemoveAll (Predicate<T> match);
member this.RemoveAll : Predicate<'T> -> int
Public Function RemoveAll (match As Predicate(Of T)) As Integer

参数

match
Predicate<T>

Predicate<T> 委托,用于定义要移除的元素应满足的条件。The Predicate<T> delegate that defines the conditions of the elements to remove.

返回

Int32

List<T> 中移除的元素数。The number of elements removed from the List<T>.

例外

matchnullmatch is null.

示例

下面的示例演示了 RemoveAll 使用泛型委托的方法和其他几种方法 Predicate<T>The following example demonstrates the RemoveAll method and several other methods that use the Predicate<T> generic delegate.

List<T>创建一个字符串,其中包含8个恐龙名称,其中两个名称 (在位置1,5) 以 "saurus" 结尾。A List<T> of strings is created, containing 8 dinosaur names, two of which (at positions 1 and 5) end with "saurus". 该示例还定义了一个名为的搜索谓词方法 EndsWithSaurus ,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 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".

FindFindLastFindAll 方法用于使用搜索谓词方法搜索列表。The Find, FindLast, and FindAll methods are used to search the list with the search predicate method.

RemoveAll方法用于删除以 "saurus" 结尾的所有条目。The RemoveAll method is used to remove all entries ending with "saurus". 它从头开始遍历列表,并将每个元素传递给 EndsWithSaurus 方法。It traverses the list from the beginning, passing each element in turn to the EndsWithSaurus method. 如果该方法返回,则移除该元素 EndsWithSaurus trueThe element is removed if the EndsWithSaurus method returns true.

备注

在 c # 和 Visual Basic 中,无需 Predicate<string> Predicate(Of String) 显式创建 Visual Basic) 中的委托 (。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导出正确的委托,并自动创建它。These languages infer the correct delegate from context, and create it automatically.

最后, Exists 方法验证列表中是否不存在以 "saurus" 结尾的字符串。Finally, the Exists method verifies that there are no strings in the list that end with "saurus".

using namespace System;
using namespace System::Collections::Generic;

// Search predicate returns true if a string ends in "saurus".
bool EndsWithSaurus(String^ s)
{
    return s->ToLower()->EndsWith("saurus");
};

void main()
{
    List<String^>^ dinosaurs = gcnew List<String^>();

    dinosaurs->Add("Compsognathus");
    dinosaurs->Add("Amargasaurus");
    dinosaurs->Add("Oviraptor");
    dinosaurs->Add("Velociraptor");
    dinosaurs->Add("Deinonychus");
    dinosaurs->Add("Dilophosaurus");
    dinosaurs->Add("Gallimimus");
    dinosaurs->Add("Triceratops");

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

    Console::WriteLine("\nTrueForAll(EndsWithSaurus): {0}",
        dinosaurs->TrueForAll(gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nFind(EndsWithSaurus): {0}", 
        dinosaurs->Find(gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nFindLast(EndsWithSaurus): {0}",
        dinosaurs->FindLast(gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nFindAll(EndsWithSaurus):");
    List<String^>^ sublist = 
        dinosaurs->FindAll(gcnew Predicate<String^>(EndsWithSaurus));

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

    Console::WriteLine(
        "\n{0} elements removed by RemoveAll(EndsWithSaurus).", 
        dinosaurs->RemoveAll(gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nList now contains:");
    for each(String^ dinosaur in dinosaurs)
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\nExists(EndsWithSaurus): {0}", 
        dinosaurs->Exists(gcnew Predicate<String^>(EndsWithSaurus)));
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

TrueForAll(EndsWithSaurus): False

Find(EndsWithSaurus): Amargasaurus

FindLast(EndsWithSaurus): Dilophosaurus

FindAll(EndsWithSaurus):
Amargasaurus
Dilophosaurus

2 elements removed by RemoveAll(EndsWithSaurus).

List now contains:
Compsognathus
Oviraptor
Velociraptor
Deinonychus
Gallimimus
Triceratops

Exists(EndsWithSaurus): False
 */
using System;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        List<string> dinosaurs = new List<string>();

        dinosaurs.Add("Compsognathus");
        dinosaurs.Add("Amargasaurus");
        dinosaurs.Add("Oviraptor");
        dinosaurs.Add("Velociraptor");
        dinosaurs.Add("Deinonychus");
        dinosaurs.Add("Dilophosaurus");
        dinosaurs.Add("Gallimimus");
        dinosaurs.Add("Triceratops");

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

        Console.WriteLine("\nTrueForAll(EndsWithSaurus): {0}",
            dinosaurs.TrueForAll(EndsWithSaurus));

        Console.WriteLine("\nFind(EndsWithSaurus): {0}",
            dinosaurs.Find(EndsWithSaurus));

        Console.WriteLine("\nFindLast(EndsWithSaurus): {0}",
            dinosaurs.FindLast(EndsWithSaurus));

        Console.WriteLine("\nFindAll(EndsWithSaurus):");
        List<string> sublist = dinosaurs.FindAll(EndsWithSaurus);

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

        Console.WriteLine(
            "\n{0} elements removed by RemoveAll(EndsWithSaurus).",
            dinosaurs.RemoveAll(EndsWithSaurus));

        Console.WriteLine("\nList now contains:");
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine("\nExists(EndsWithSaurus): {0}",
            dinosaurs.Exists(EndsWithSaurus));
    }

    // Search predicate returns true if a string ends in "saurus".
    private static bool EndsWithSaurus(String s)
    {
        return s.ToLower().EndsWith("saurus");
    }
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

TrueForAll(EndsWithSaurus): False

Find(EndsWithSaurus): Amargasaurus

FindLast(EndsWithSaurus): Dilophosaurus

FindAll(EndsWithSaurus):
Amargasaurus
Dilophosaurus

2 elements removed by RemoveAll(EndsWithSaurus).

List now contains:
Compsognathus
Oviraptor
Velociraptor
Deinonychus
Gallimimus
Triceratops

Exists(EndsWithSaurus): False
 */
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs As New List(Of String)

        dinosaurs.Add("Compsognathus")
        dinosaurs.Add("Amargasaurus")
        dinosaurs.Add("Oviraptor")
        dinosaurs.Add("Velociraptor")
        dinosaurs.Add("Deinonychus")
        dinosaurs.Add("Dilophosaurus")
        dinosaurs.Add("Gallimimus")
        dinosaurs.Add("Triceratops")

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

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

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

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

        Console.WriteLine(vbLf & _
            "FindAll(AddressOf EndsWithSaurus):")
        Dim sublist As List(Of String) = _
            dinosaurs.FindAll(AddressOf EndsWithSaurus)

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

        Console.WriteLine(vbLf & _
            "{0} elements removed by RemoveAll(AddressOf EndsWithSaurus).", _
            dinosaurs.RemoveAll(AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & "List now contains:")
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & _
            "Exists(AddressOf EndsWithSaurus): {0}", _
            dinosaurs.Exists(AddressOf EndsWithSaurus))
        
    End Sub

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

        Return s.ToLower().EndsWith("saurus")
    End Function
End Class

' This code example produces the following output:
'
'Compsognathus
'Amargasaurus
'Oviraptor
'Velociraptor
'Deinonychus
'Dilophosaurus
'Gallimimus
'Triceratops
'
'TrueForAll(AddressOf EndsWithSaurus: False
'
'Find(AddressOf EndsWithSaurus): Amargasaurus
'
'FindLast(AddressOf EndsWithSaurus): Dilophosaurus
'
'FindAll(AddressOf EndsWithSaurus):
'Amargasaurus
'Dilophosaurus
'
'2 elements removed by RemoveAll(AddressOf EndsWithSaurus).
'
'List now contains:
'Compsognathus
'Oviraptor
'Velociraptor
'Deinonychus
'Gallimimus
'Triceratops
'
'Exists(AddressOf EndsWithSaurus): False

注解

Predicate<T>是一个方法委托, true 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。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. 将当前的元素 List<T> 分别传递到 Predicate<T> 委托,并从中删除与条件相匹配的元素 List<T>The elements of the current List<T> are individually passed to the Predicate<T> delegate, and the elements that match the conditions are removed from the List<T>.

此方法执行线性搜索;因此,此方法是 O (n) 操作,其中 nCountThis method performs a linear search; therefore, this method is an O(n) operation, where n is Count.

适用于

另请参阅