HashSet<T> 构造函数

参考

定义

命名空间:: System.Collections.Generic

程序集:: System.Collections.dll

程序集:: System.Core.dll

程序集:: netstandard.dll

重要

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初始化 HashSet<T> 类的新实例。

重载

HashSet<T>()	初始化 HashSet<T> 类的一个新实例，该实例为空并使用集类型的默认相等比较器。
HashSet<T>(IEnumerable<T>)	初始化 HashSet<T> 类的一个新实例，该实例使用集类型的默认相等比较器，包含从指定的集合复制的元素，并且有足够的容量容纳所复制的这些元素。
HashSet<T>(IEqualityComparer<T>)	初始化 HashSet<T> 类的一个新实例，该实例为空并使用集类型的指定相等比较器。
HashSet<T>(Int32)	初始化 HashSet<T> 类的一个新实例，该实例为空，但已为 `capacity` 项保留空间并使用集类型的默认相等比较器。
HashSet<T>(IEnumerable<T>, IEqualityComparer<T>)	初始化 HashSet<T> 类的一个新实例，该实例使用集类型的指定相等比较器，包含从指定的集合复制的元素，并且有足够的容量容纳所复制的这些元素。
HashSet<T>(Int32, IEqualityComparer<T>)	初始化 HashSet<T> 类的新实例，该实例使用集类型的指定相等比较器，并且其容量足以容纳 `capacity` 元素。
HashSet<T>(SerializationInfo, StreamingContext)	已过时. 用序列化数据初始化 HashSet<T> 类的新实例。

HashSet<T>()

Source:: HashSet.cs

Source:: HashSet.cs

Source:: HashSet.cs

初始化 HashSet<T> 类的一个新实例，该实例为空并使用集类型的默认相等比较器。

public:
 HashSet();

public HashSet ();

Public Sub New ()

示例

以下示例演示如何创建和填充两个 HashSet<T> 对象。此示例是为方法提供的更大示例的 UnionWith 一部分。

HashSet<int> evenNumbers = new HashSet<int>();
HashSet<int> oddNumbers = new HashSet<int>();

for (int i = 0; i < 5; i++)
{
    // Populate numbers with just even numbers.
    evenNumbers.Add(i * 2);

    // Populate oddNumbers with just odd numbers.
    oddNumbers.Add((i * 2) + 1);
}

Dim evenNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()
Dim oddNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()

For i As Integer = 0 To 4

    ' Populate evenNumbers with only even numbers.
    evenNumbers.Add(i * 2)

    ' Populate oddNumbers with only odd numbers.
    oddNumbers.Add((i * 2) + 1)
Next i

注解

对象的容量 HashSet<T> 是对象可以容纳的元素数。当 HashSet<T> 元素添加到对象时，对象的容量会自动增加。

此构造函数是一个 O (1) 操作。

适用于

HashSet<T>(IEnumerable<T>)

Source:: HashSet.cs

Source:: HashSet.cs

Source:: HashSet.cs

初始化 HashSet<T> 类的一个新实例，该实例使用集类型的默认相等比较器，包含从指定的集合复制的元素，并且有足够的容量容纳所复制的这些元素。

public:
 HashSet(System::Collections::Generic::IEnumerable<T> ^ collection);

public HashSet (System.Collections.Generic.IEnumerable<T> collection);

new System.Collections.Generic.HashSet<'T> : seq<'T> -> System.Collections.Generic.HashSet<'T>

Public Sub New (collection As IEnumerable(Of T))

参数

collection: IEnumerable<T>

其元素被复制到新集中的集合。

例外

ArgumentNullException

collection 为 null。

示例

以下示例演示如何从现有集创建 HashSet<T> 集合。在此示例中，分别使用偶数和奇数创建两个集。然后，从偶数整数集创建第三 HashSet<T> 个对象。

HashSet<int> evenNumbers = new HashSet<int>();
HashSet<int> oddNumbers = new HashSet<int>();

for (int i = 0; i < 5; i++)
{
    // Populate numbers with just even numbers.
    evenNumbers.Add(i * 2);

    // Populate oddNumbers with just odd numbers.
    oddNumbers.Add((i * 2) + 1);
}

Console.Write("evenNumbers contains {0} elements: ", evenNumbers.Count);
DisplaySet(evenNumbers);

Console.Write("oddNumbers contains {0} elements: ", oddNumbers.Count);
DisplaySet(oddNumbers);

// Create a new HashSet populated with even numbers.
HashSet<int> numbers = new HashSet<int>(evenNumbers);
Console.WriteLine("numbers UnionWith oddNumbers...");
numbers.UnionWith(oddNumbers);

Console.Write("numbers contains {0} elements: ", numbers.Count);
DisplaySet(numbers);

void DisplaySet(HashSet<int> collection)
{
    Console.Write("{");
    foreach (int i in collection)
    {
        Console.Write(" {0}", i);
    }
    Console.WriteLine(" }");
}

/* This example produces output similar to the following:
* evenNumbers contains 5 elements: { 0 2 4 6 8 }
* oddNumbers contains 5 elements: { 1 3 5 7 9 }
* numbers UnionWith oddNumbers...
* numbers contains 10 elements: { 0 2 4 6 8 1 3 5 7 9 }
*/

Shared Sub Main()

    Dim evenNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()
    Dim oddNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()

    For i As Integer = 0 To 4

        ' Populate evenNumbers with only even numbers.
        evenNumbers.Add(i * 2)

        ' Populate oddNumbers with only odd numbers.
        oddNumbers.Add((i * 2) + 1)
    Next i

    Console.Write("evenNumbers contains {0} elements: ", evenNumbers.Count)
    DisplaySet(evenNumbers)

    Console.Write("oddNumbers contains {0} elements: ", oddNumbers.Count)
    DisplaySet(oddNumbers)

    ' Create a new HashSet populated with even numbers.
    Dim numbers As HashSet(Of Integer) = New HashSet(Of Integer)(evenNumbers)
    Console.WriteLine("numbers UnionWith oddNumbers...")
    numbers.UnionWith(oddNumbers)

    Console.Write("numbers contains {0} elements: ", numbers.Count)
    DisplaySet(numbers)
End Sub

注解

对象的容量 HashSet<T> 是对象可以容纳的元素数。当 HashSet<T> 元素添加到对象时，对象的容量会自动增加。

如果 collection 包含重复项，则集将包含每个唯一元素之一。不会引发异常。因此，生成的集的大小与的大小 collection不同。

此构造函数是一个 O (n) 操作，其中 n 是参数中的 collection 元素数。

适用于

HashSet<T>(IEqualityComparer<T>)

Source:: HashSet.cs

Source:: HashSet.cs

Source:: HashSet.cs

初始化 HashSet<T> 类的一个新实例，该实例为空并使用集类型的指定相等比较器。

public:
 HashSet(System::Collections::Generic::IEqualityComparer<T> ^ comparer);

public HashSet (System.Collections.Generic.IEqualityComparer<T> comparer);

public HashSet (System.Collections.Generic.IEqualityComparer<T>? comparer);

new System.Collections.Generic.HashSet<'T> : System.Collections.Generic.IEqualityComparer<'T> -> System.Collections.Generic.HashSet<'T>

Public Sub New (comparer As IEqualityComparer(Of T))

参数

comparer: IEqualityComparer<T>

在比较集中的值时使用的 IEqualityComparer<T> 实现，或为 null 以使用集类型的默认 EqualityComparer<T> 实现。

注解

对象的容量 HashSet<T> 是对象可以容纳的元素数。当 HashSet<T> 元素添加到对象时，对象的容量会自动增加。

此构造函数是一个 O (1) 操作。

适用于

HashSet<T>(Int32)

Source:: HashSet.cs

Source:: HashSet.cs

Source:: HashSet.cs

初始化 HashSet<T> 类的一个新实例，该实例为空，但已为 capacity 项保留空间并使用集类型的默认相等比较器。

public:
 HashSet(int capacity);

public HashSet (int capacity);

new System.Collections.Generic.HashSet<'T> : int -> System.Collections.Generic.HashSet<'T>

Public Sub New (capacity As Integer)

参数

capacity: Int32

的初始大小 HashSet<T>。

注解

由于重设大小是相对昂贵的 (需要重新) ，因此这会尝试通过基于的值 capacity设置初始容量来最大程度地减少重设大小的需求。

适用于

HashSet<T>(IEnumerable<T>, IEqualityComparer<T>)

Source:: HashSet.cs

Source:: HashSet.cs

Source:: HashSet.cs

初始化 HashSet<T> 类的一个新实例，该实例使用集类型的指定相等比较器，包含从指定的集合复制的元素，并且有足够的容量容纳所复制的这些元素。

public:
 HashSet(System::Collections::Generic::IEnumerable<T> ^ collection, System::Collections::Generic::IEqualityComparer<T> ^ comparer);

public HashSet (System.Collections.Generic.IEnumerable<T> collection, System.Collections.Generic.IEqualityComparer<T> comparer);

public HashSet (System.Collections.Generic.IEnumerable<T> collection, System.Collections.Generic.IEqualityComparer<T>? comparer);

new System.Collections.Generic.HashSet<'T> : seq<'T> * System.Collections.Generic.IEqualityComparer<'T> -> System.Collections.Generic.HashSet<'T>

Public Sub New (collection As IEnumerable(Of T), comparer As IEqualityComparer(Of T))

参数

collection: IEnumerable<T>

其元素被复制到新集中的集合。

comparer: IEqualityComparer<T>

在比较集中的值时使用的 IEqualityComparer<T> 实现，或为 null 以使用集类型的默认 EqualityComparer<T> 实现。

例外

ArgumentNullException

collection 为 null。

示例

以下示例使用提供的 IEqualityComparer<T> ，允许对车辆类型集合的 HashSet<T> 元素进行不区分大小写的比较。

#using <System.Core.dll>

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

ref class Program
{
public:
    static void Main()
    {
        HashSet<String^> ^allVehicles = gcnew HashSet<String^>(StringComparer::OrdinalIgnoreCase);
        List<String^>^ someVehicles = gcnew List<String^>();

        someVehicles->Add("Planes");
        someVehicles->Add("Trains");
        someVehicles->Add("Automobiles");

        // Add in the vehicles contained in the someVehicles list.
        allVehicles->UnionWith(someVehicles);

        Console::WriteLine("The current HashSet contains:\n");
        for each (String^ vehicle in allVehicles)
        {
            Console::WriteLine(vehicle);
        }

        allVehicles->Add("Ships");
        allVehicles->Add("Motorcycles");
        allVehicles->Add("Rockets");
        allVehicles->Add("Helicopters");
        allVehicles->Add("Submarines");

        Console::WriteLine("\nThe updated HashSet contains:\n");
        for each (String^ vehicle in allVehicles)
        {
            Console::WriteLine(vehicle);
        }

        // Verify that the 'All Vehicles' set contains at least the vehicles in
        // the 'Some Vehicles' list.
        if (allVehicles->IsSupersetOf(someVehicles))
        {
            Console::Write("\nThe 'All' vehicles set contains everything in ");
            Console::WriteLine("'Some' vechicles list.");
        }

        // Check for Rockets. Here the OrdinalIgnoreCase comparer will compare
        // true for the mixed-case vehicle type.
        if (allVehicles->Contains("roCKeTs"))
        {
            Console::WriteLine("\nThe 'All' vehicles set contains 'roCKeTs'");
        }

        allVehicles->ExceptWith(someVehicles);
        Console::WriteLine("\nThe excepted HashSet contains:\n");
        for each (String^ vehicle in allVehicles)
        {
            Console::WriteLine(vehicle);
        }

        // Remove all the vehicles that are not 'super cool'.
        allVehicles->RemoveWhere(gcnew Predicate<String^>(&isNotSuperCool));

        Console::WriteLine("\nThe super cool vehicles are:\n");
        for each (String^ vehicle in allVehicles)
        {
            Console::WriteLine(vehicle);
        }
    }

private:
    // Predicate to determine vehicle 'coolness'.
    static bool isNotSuperCool(String^ vehicle)
    {
        bool superCool = (vehicle == "Helicopters") || (vehicle == "Motorcycles");

        return !superCool;
    }
};

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

// The program writes the following output to the console::
//
// The current HashSet contains:
//
// Planes
// Trains
// Automobiles
//
// The updated HashSet contains:
//
// Planes
// Trains
// Automobiles
// Ships
// Motorcycles
// Rockets
// Helicopters
// Submarines
//
// The 'All' vehicles set contains everything in 'Some' vechicles list.
//
// The 'All' vehicles set contains 'roCKeTs'
//
// The excepted HashSet contains:
//
// Ships
// Motorcycles
// Rockets
// Helicopters
// Submarines
//
// The super cool vehicles are:
//
// Motorcycles
// Helicopters

HashSet<string> allVehicles = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
List<string> someVehicles = new List<string>();

someVehicles.Add("Planes");
someVehicles.Add("Trains");
someVehicles.Add("Automobiles");

// Add in the vehicles contained in the someVehicles list.
allVehicles.UnionWith(someVehicles);

Console.WriteLine("The current HashSet contains:\n");
foreach (string vehicle in allVehicles)
{
    Console.WriteLine(vehicle);
}

allVehicles.Add("Ships");
allVehicles.Add("Motorcycles");
allVehicles.Add("Rockets");
allVehicles.Add("Helicopters");
allVehicles.Add("Submarines");

Console.WriteLine("\nThe updated HashSet contains:\n");
foreach (string vehicle in allVehicles)
{
    Console.WriteLine(vehicle);
}

// Verify that the 'All Vehicles' set contains at least the vehicles in
// the 'Some Vehicles' list.
if (allVehicles.IsSupersetOf(someVehicles))
{
    Console.Write("\nThe 'All' vehicles set contains everything in ");
    Console.WriteLine("'Some' vechicles list.");
}

// Check for Rockets. Here the OrdinalIgnoreCase comparer will compare
// true for the mixed-case vehicle type.
if (allVehicles.Contains("roCKeTs"))
{
    Console.WriteLine("\nThe 'All' vehicles set contains 'roCKeTs'");
}

allVehicles.ExceptWith(someVehicles);
Console.WriteLine("\nThe excepted HashSet contains:\n");
foreach (string vehicle in allVehicles)
{
    Console.WriteLine(vehicle);
}

// Remove all the vehicles that are not 'super cool'.
allVehicles.RemoveWhere(isNotSuperCool);

Console.WriteLine("\nThe super cool vehicles are:\n");
foreach (string vehicle in allVehicles)
{
    Console.WriteLine(vehicle);
}

// Predicate to determine vehicle 'coolness'.
bool isNotSuperCool(string vehicle)
{
    bool superCool = (vehicle == "Helicopters") || (vehicle == "Motorcycles");

    return !superCool;
}

// The program writes the following output to the console.
//
// The current HashSet contains:
//
// Planes
// Trains
// Automobiles
//
// The updated HashSet contains:
//
// Planes
// Trains
// Automobiles
// Ships
// Motorcycles
// Rockets
// Helicopters
// Submarines
//
// The 'All' vehicles set contains everything in 'Some' vechicles list.
//
// The 'All' vehicles set contains 'roCKeTs'
//
// The excepted HashSet contains:
//
// Ships
// Motorcycles
// Rockets
// Helicopters
// Submarines
//
// The super cool vehicles are:
//
// Motorcycles
// Helicopters

Imports System.Collections.Generic

Class Program
    Public Shared Sub Main()
        Dim allVehicles As New HashSet(Of String)(StringComparer.OrdinalIgnoreCase)
        Dim someVehicles As New List(Of String)()

        someVehicles.Add("Planes")
        someVehicles.Add("Trains")
        someVehicles.Add("Automobiles")

        ' Add in the vehicles contained in the someVehicles list.
        allVehicles.UnionWith(someVehicles)

        Console.WriteLine("The current HashSet contains:" + Environment.NewLine)
        For Each vehicle As String In allVehicles
            Console.WriteLine(vehicle)
        Next vehicle

        allVehicles.Add("Ships")
        allVehicles.Add("Motorcycles")
        allVehicles.Add("Rockets")
        allVehicles.Add("Helicopters")
        allVehicles.Add("Submarines")

        Console.WriteLine(Environment.NewLine + "The updated HashSet contains:" + Environment.NewLine)
        For Each vehicle As String In allVehicles
            Console.WriteLine(vehicle)
        Next vehicle

        ' Verify that the 'All Vehicles' set contains at least the vehicles in
        ' the 'Some Vehicles' list.
        If allVehicles.IsSupersetOf(someVehicles) Then
            Console.Write(Environment.NewLine + "The 'All' vehicles set contains everything in ")
            Console.WriteLine("'Some' vechicles list.")
        End If

        ' Check for Rockets. Here the OrdinalIgnoreCase comparer will compare
        ' True for the mixed-case vehicle type.
        If allVehicles.Contains("roCKeTs") Then
            Console.WriteLine(Environment.NewLine + "The 'All' vehicles set contains 'roCKeTs'")
        End If

        allVehicles.ExceptWith(someVehicles)
        Console.WriteLine(Environment.NewLine + "The excepted HashSet contains:" + Environment.NewLine)
        For Each vehicle As String In allVehicles
            Console.WriteLine(vehicle)
        Next vehicle

        ' Remove all the vehicles that are not 'super cool'.
        allVehicles.RemoveWhere(AddressOf isNotSuperCool)

        Console.WriteLine(Environment.NewLine + "The super cool vehicles are:" + Environment.NewLine)
        For Each vehicle As String In allVehicles
            Console.WriteLine(vehicle)
        Next vehicle
    End Sub

    ' Predicate to determine vehicle 'coolness'.
    Private Shared Function isNotSuperCool(vehicle As String) As Boolean
        Dim notSuperCool As Boolean = _
            (vehicle <> "Helicopters") And (vehicle <> "Motorcycles")

        Return notSuperCool
    End Function
End Class

'
' The program writes the following output to the console.
'
' The current HashSet contains:
'
' Planes
' Trains
' Automobiles
'
' The updated HashSet contains:
'
' Planes
' Trains
' Automobiles
' Ships
' Motorcycles
' Rockets
' Helicopters
' Submarines
'
' The 'All' vehicles set contains everything in 'Some' vechicles list.
'
' The 'All' vehicles set contains 'roCKeTs'
'
' The excepted HashSet contains:
'
' Ships
' Motorcycles
' Rockets
' Helicopters
' Submarines
'
' The super cool vehicles are:
'
' Motorcycles
' Helicopters

注解

对象的容量 HashSet<T> 是对象可以容纳的元素数。当 HashSet<T> 元素添加到对象时，对象的容量会自动增加。

如果 collection 包含重复项，则集将包含每个唯一元素之一。不会引发异常。因此，生成的集的大小与的大小 collection不同。

此构造函数是一个 O (n) 操作，其中 n 是参数中的 collection 元素数。

适用于

HashSet<T>(Int32, IEqualityComparer<T>)

Source:: HashSet.cs

Source:: HashSet.cs

Source:: HashSet.cs

初始化 HashSet<T> 类的新实例，该实例使用集类型的指定相等比较器，并且其容量足以容纳 capacity 元素。

public:
 HashSet(int capacity, System::Collections::Generic::IEqualityComparer<T> ^ comparer);

public HashSet (int capacity, System.Collections.Generic.IEqualityComparer<T>? comparer);

public HashSet (int capacity, System.Collections.Generic.IEqualityComparer<T> comparer);

new System.Collections.Generic.HashSet<'T> : int * System.Collections.Generic.IEqualityComparer<'T> -> System.Collections.Generic.HashSet<'T>

Public Sub New (capacity As Integer, comparer As IEqualityComparer(Of T))

参数

capacity: Int32

的初始大小 HashSet<T>。

comparer: IEqualityComparer<T>

比较集中的值时使用的 IEqualityComparer<T> 实现；如果要使用集类型的默认 IEqualityComparer<T> 实现，则为 null（在 Visual Basic 中为 Nothing）。

注解

由于重设大小是相对昂贵的 (需要重新) ，因此这会尝试通过基于的值 capacity设置初始容量来最大程度地减少重设大小的需求。

适用于

HashSet<T>(SerializationInfo, StreamingContext)

Source:: HashSet.cs

Source:: HashSet.cs

Source:: HashSet.cs

注意

This API supports obsolete formatter-based serialization. It should not be called or extended by application code.

用序列化数据初始化 HashSet<T> 类的新实例。

protected:
 HashSet(System::Runtime::Serialization::SerializationInfo ^ info, System::Runtime::Serialization::StreamingContext context);

protected HashSet (System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context);

[System.Obsolete("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
protected HashSet (System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context);

new System.Collections.Generic.HashSet<'T> : System.Runtime.Serialization.SerializationInfo * System.Runtime.Serialization.StreamingContext -> System.Collections.Generic.HashSet<'T>

[<System.Obsolete("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")>]
new System.Collections.Generic.HashSet<'T> : System.Runtime.Serialization.SerializationInfo * System.Runtime.Serialization.StreamingContext -> System.Collections.Generic.HashSet<'T>

Protected Sub New (info As SerializationInfo, context As StreamingContext)

参数

info: SerializationInfo

SerializationInfo 对象，其中包含序列化 HashSet<T> 对象所需的信息。

context: StreamingContext

StreamingContext 结构，其中包含与 HashSet<T> 对象关联的序列化流的源和目标。

属性: ObsoleteAttribute

注解

在反序列化期间调用此构造函数，以重新构造通过流传输的对象。有关详细信息，请参阅 XML 和 SOAP 序列化。

适用于

HashSet<T> 构造函数

定义

重载

HashSet<T>()

示例

注解

适用于

HashSet<T>(IEnumerable<T>)

参数

例外

示例

注解

适用于

HashSet<T>(IEqualityComparer<T>)

参数

注解

适用于

HashSet<T>(Int32)

参数

注解

适用于

HashSet<T>(IEnumerable<T>, IEqualityComparer<T>)

参数

例外

示例

注解

适用于

HashSet<T>(Int32, IEqualityComparer<T>)

参数

注解

适用于

HashSet<T>(SerializationInfo, StreamingContext)

参数

注解

适用于

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