Поделиться через

HashCode Структура

  • Ссылка

Определение

Пространство имен:
System
Сборка:
System.Runtime.dll
Сборка:
Microsoft.Bcl.HashCode.dll
Сборка:
netstandard.dll
Пакет:
Microsoft.Bcl.HashCode v1.1.1
Исходный код:
HashCode.cs
Исходный код:
HashCode.cs
Исходный код:
HashCode.cs

Объединяет хэш-код для нескольких значений в один хэш-код.

public value class HashCode
public struct HashCode
type HashCode = struct
Public Structure HashCode
Наследование
Object
ValueType
HashCode

Примеры

Статические методы в этом классе объединяют хэш-коды по умолчанию не более восьми значений.

using System;
using System.Collections.Generic;

public struct OrderOrderLine : IEquatable<OrderOrderLine>
{
    public int OrderId { get; }
    public int OrderLineId { get; }

    public OrderOrderLine(int orderId, int orderLineId) => (OrderId, OrderLineId) = (orderId, orderLineId);

    public override bool Equals(object obj) => obj is OrderOrderLine o && Equals(o);

    public bool Equals(OrderOrderLine other) => OrderId == other.OrderId && OrderLineId == other.OrderLineId;

    public override int GetHashCode() => HashCode.Combine(OrderId, OrderLineId);
}

class Program
{
    static void Main(string[] args)
    {
        var set = new HashSet<OrderOrderLine>
        {
            new OrderOrderLine(1, 1),
            new OrderOrderLine(1, 1),
            new OrderOrderLine(1, 2)
        };

        Console.WriteLine($"Item count: {set.Count}.");
    }
}
// The example displays the following output:
// Item count: 2.

open System
open System.Collections.Generic

[<Struct; CustomEquality; NoComparison>]
type OrderOrderLine(orderId: int, orderLineId: int) =
    member _.OrderId = orderId
    member _.OrderLineId = orderLineId

    override _.GetHashCode() = 
        HashCode.Combine(orderId, orderLineId)

    override this.Equals(obj) =
        match obj with
        | :? OrderOrderLine as o -> (this :> IEquatable<_>).Equals o
        | _ -> false

    interface IEquatable<OrderOrderLine> with
        member _.Equals(other: OrderOrderLine) = 
            orderId = other.OrderId && orderLineId = other.OrderLineId

let set =
    HashSet<OrderOrderLine> [ OrderOrderLine(1, 1); OrderOrderLine(1, 1); OrderOrderLine(1, 2) ]
printfn $"Item count: {set.Count}."

// The example displays the following output:
// Item count: 2.

Public Structure OrderOrderLine
    Implements IEquatable(Of OrderOrderLine)

    Public ReadOnly Property OrderId As Integer
    Public ReadOnly Property OrderLineId As Integer

    Public Sub New(ByVal orderId As Integer, ByVal orderLineId As Integer)
        Me.OrderId = orderId
        Me.OrderLineId = orderLineId
    End Sub

    Public Overrides Function Equals(obj As Object) As Boolean
        Return (TypeOf obj Is OrderOrderLine) AndAlso Equals(DirectCast(obj, OrderOrderLine))
    End Function

    Public Overloads Function Equals(other As OrderOrderLine) As Boolean Implements IEquatable(Of OrderOrderLine).Equals
        Return OrderId = other.OrderId AndAlso
               OrderLineId = other.OrderLineId
    End Function

    Public Overrides Function GetHashCode() As Integer
        Return HashCode.Combine(OrderId, OrderLineId)
    End Function

End Structure

Module Program

    Sub Main(args As String())
        Dim hashSet As HashSet(Of OrderOrderLine) = New HashSet(Of OrderOrderLine)
        hashSet.Add(New OrderOrderLine(1, 1))
        hashSet.Add(New OrderOrderLine(1, 1))
        hashSet.Add(New OrderOrderLine(1, 2))
        Console.WriteLine($"Item count: {hashSet.Count}")
    End Sub

End Module
' The example displays the following output:
' Item count: 2.

Важно!

ToHashCode() должен вызываться не более одного раза для каждого экземпляра HashCode.

Методы экземпляра в этом классе объединяют хэш-коды более восьми значений.

using System;
using System.Collections.Generic;

public struct Path : IEquatable<Path>
{
    public IReadOnlyList<string> Segments { get; }

    public Path(params string[] segments) => Segments = segments;

    public override bool Equals(object obj) => obj is Path o && Equals(o);

    public bool Equals(Path other)
    {
        if (ReferenceEquals(Segments, other.Segments)) return true;
        if (Segments is null || other.Segments is null) return false;
        if (Segments.Count != other.Segments.Count) return false;

        for (var i = 0; i < Segments.Count; i++)
        {
            if (!string.Equals(Segments[i], other.Segments[i]))
                return false;
        }

        return true;
    }

    public override int GetHashCode()
    {
        var hash = new HashCode();

        for (var i = 0; i < Segments?.Count; i++)
            hash.Add(Segments[i]);

        return hash.ToHashCode();
    }
}

class Program
{
    static void Main(string[] args)
    {
        var set = new HashSet<Path>
        {
            new Path("C:", "tmp", "file.txt"),
            new Path("C:", "tmp", "file.txt"),
            new Path("C:", "tmp", "file.tmp")
        };

        Console.WriteLine($"Item count: {set.Count}.");
    }
}
// The example displays the following output:
// Item count: 2.

open System
open System.Collections.Generic

[<Struct; CustomEquality; NoComparison>]
type Path([<ParamArray>]segments: string[]) = 
    member _.Segments = 
        Array.AsReadOnly segments

    override this.Equals(obj) =
        match obj with
        | :? Path as o -> (this :> IEquatable<_>).Equals(o)
        | _ -> false

    interface IEquatable<Path> with
        member this.Equals(other: Path) =
            Object.ReferenceEquals(this.Segments, other.Segments) ||
            not (isNull this.Segments) && 
            not (isNull other.Segments) &&
            this.Segments.Count = other.Segments.Count &&
            Seq.forall2 (=) this.Segments other.Segments 

    override this.GetHashCode() =
        let hash = HashCode()

        for i = 0 to this.Segments.Count - 1 do
            hash.Add this.Segments[i]
        hash.ToHashCode()

let set = 
    HashSet<Path> [
        Path("C:", "tmp", "file.txt")
        Path("C:", "tmp", "file.tmp")
        Path("C:", "tmp", "file.txt") ]
        
printfn $"Item count: {set.Count}."

// The example displays the following output:
// Item count: 2.

Public Structure Path
    Implements IEquatable(Of Path)

    Public ReadOnly Property Segments As IReadOnlyList(Of String)

    Public Sub New(ParamArray ByVal segments() As String)
        Me.Segments = segments
    End Sub

    Public Overrides Function Equals(obj As Object) As Boolean
        Return (TypeOf obj Is Path) AndAlso Equals(DirectCast(obj, Path))
    End Function

    Public Overloads Function Equals(other As Path) As Boolean Implements IEquatable(Of Path).Equals
        If ReferenceEquals(Segments, other.Segments) Then Return True
        If Segments Is Nothing OrElse other.Segments Is Nothing Then Return False
        If Segments.Count <> other.Segments.Count Then Return False

        For i As Integer = 0 To Segments.Count - 1
            If Not String.Equals(Segments(i), other.Segments(i)) Then Return False
        Next

        Return True
    End Function

    Public Overrides Function GetHashCode() As Integer
        Dim hash As HashCode = New HashCode()

        For i As Integer = 0 To Segments?.Count - 1
            hash.Add(Segments(i))
        Next

        Return hash.ToHashCode()
    End Function

End Structure

Module Program

    Sub Main(args As String())
        Dim hashSet As HashSet(Of Path) = New HashSet(Of Path) From {
            New Path("C:", "tmp", "file.txt"),
            New Path("C:", "tmp", "file.txt"),
            New Path("C:", "tmp", "file.tmp")
        }
        Console.WriteLine($"Item count: {hashSet.Count}.")
    End Sub

End Module
' The example displays the following output:
' Item count: 2.

Методы экземпляра также объединяют хэш-коды, созданные определенной IEqualityComparer<T> реализацией.

using System;
using System.Collections.Generic;

public struct Path : IEquatable<Path>
{
    public IReadOnlyList<string> Segments { get; }

    public Path(params string[] segments) => Segments = segments;

    public override bool Equals(object obj) => obj is Path o && Equals(o);

    public bool Equals(Path other)
    {
        if (ReferenceEquals(Segments, other.Segments)) return true;
        if (Segments is null || other.Segments is null) return false;
        if (Segments.Count != other.Segments.Count) return false;

        for (var i = 0; i < Segments.Count; i++)
        {
            if (!string.Equals(Segments[i], other.Segments[i], StringComparison.OrdinalIgnoreCase))
                return false;
        }

        return true;
    }

    public override int GetHashCode()
    {
        var hash = new HashCode();

        for (var i = 0; i < Segments?.Count; i++)
            hash.Add(Segments[i], StringComparer.OrdinalIgnoreCase);

        return hash.ToHashCode();
    }
}

class Program
{
    static void Main(string[] args)
    {
        var set = new HashSet<Path>
        {
            new Path("C:", "tmp", "file.txt"),
            new Path("C:", "TMP", "file.txt"),
            new Path("C:", "tmp", "FILE.TXT")
        };

        Console.WriteLine($"Item count: {set.Count}.");
    }
}
// The example displays the following output:
// Item count: 1.

open System
open System.Collections.Generic

[<Struct; CustomEquality; NoComparison>]
type Path([<ParamArray>]segments: string[]) =
    member _.Segments = 
        Array.AsReadOnly segments

    override this.Equals(obj) =
        match obj with
        | :? Path as o -> (this :> IEquatable<_>).Equals(o)
        | _ -> false

    interface IEquatable<Path> with
        member this.Equals(other: Path) =
            Object.ReferenceEquals(this.Segments, other.Segments) ||
            not (isNull this.Segments) && 
            not (isNull other.Segments) &&
            this.Segments.Count = other.Segments.Count &&
            Seq.forall2 (fun x y -> String.Equals(x, y, StringComparison.OrdinalIgnoreCase)) this.Segments other.Segments 

    override this.GetHashCode() =
        let hash = HashCode()

        for i = 0 to this.Segments.Count - 1 do
            hash.Add(this.Segments[i], StringComparer.OrdinalIgnoreCase)
        hash.ToHashCode()

let set = 
    HashSet<Path> [
        Path("C:", "tmp", "file.txt")
        Path("C:", "tmp", "file.tmp")
        Path("C:", "tmp", "file.txt") ]

printfn $"Item count: {set.Count}."

// The example displays the following output:
// Item count: 1.

Public Structure Path
    Implements IEquatable(Of Path)

    Public ReadOnly Property Segments As IReadOnlyList(Of String)

    Public Sub New(ParamArray ByVal segments() As String)
        Me.Segments = segments
    End Sub

    Public Overrides Function Equals(obj As Object) As Boolean
        Return (TypeOf obj Is Path) AndAlso Equals(DirectCast(obj, Path))
    End Function

    Public Overloads Function Equals(other As Path) As Boolean Implements IEquatable(Of Path).Equals
        If ReferenceEquals(Segments, other.Segments) Then Return True
        If Segments Is Nothing OrElse other.Segments Is Nothing Then Return False
        If Segments.Count <> other.Segments.Count Then Return False

        For i As Integer = 0 To Segments.Count - 1
            If Not String.Equals(Segments(i), other.Segments(i), StringComparison.OrdinalIgnoreCase) Then Return False
        Next

        Return True
    End Function

    Public Overrides Function GetHashCode() As Integer
        Dim hash As HashCode = New HashCode()

        For i As Integer = 0 To Segments?.Count - 1
            hash.Add(Segments(i), StringComparer.OrdinalIgnoreCase)
        Next

        Return hash.ToHashCode()
    End Function
    
End Structure

Module Program

    Sub Main(args As String())
        Dim hashSet As HashSet(Of Path) = New HashSet(Of Path) From {
            New Path("C:", "tmp", "file.txt"),
            New Path("C:", "TMP", "file.txt"),
            New Path("C:", "tmp", "FILE.TXT")
        }
        Console.WriteLine($"Item count: {hashSet.Count}.")
    End Sub

End Module
' The example displays the following output:
' Item count: 1.

Структура HashCode должна передаваться по ссылке в другие методы, так как это тип значения.

using System;
using System.Collections.Generic;

public struct Path : IEquatable<Path>
{
    public IReadOnlyList<string> Segments { get; }

    public Path(params string[] segments) => Segments = segments;

    public override bool Equals(object obj) => obj is Path o && Equals(o);

    public bool Equals(Path other)
    {
        if (ReferenceEquals(Segments, other.Segments)) return true;
        if (Segments is null || other.Segments is null) return false;
        if (Segments.Count != other.Segments.Count) return false;

        for (var i = 0; i < Segments.Count; i++)
        {
            if (!PlatformUtils.PathEquals(Segments[i], other.Segments[i]))
                return false;
        }

        return true;
    }

    public override int GetHashCode()
    {
        var hash = new HashCode();

        for (var i = 0; i < Segments?.Count; i++)
            PlatformUtils.AddPath(ref hash, Segments[i]);

        return hash.ToHashCode();
    }
}

internal static class PlatformUtils
{
    public static bool PathEquals(string a, string b) => string.Equals(a, b, StringComparison.OrdinalIgnoreCase);
    public static void AddPath(ref HashCode hash, string path) => hash.Add(path, StringComparer.OrdinalIgnoreCase);
}

class Program
{
    static void Main(string[] args)
    {
        var set = new HashSet<Path>
        {
            new Path("C:", "tmp", "file.txt"),
            new Path("C:", "TMP", "file.txt"),
            new Path("C:", "tmp", "FILE.TXT")
        };

        Console.WriteLine($"Item count: {set.Count}.");
    }
}
// The example displays the following output:
// Item count: 1.

open System
open System.Collections.Generic

module PlatformUtils =
    let pathEquals a b = String.Equals(a, b, StringComparison.OrdinalIgnoreCase)
    let addPath (hash: byref<HashCode>) path = hash.Add(path, StringComparer.OrdinalIgnoreCase)

[<Struct; CustomEquality; NoComparison>]
type Path([<ParamArray>]segments: string[]) =
    member _.Segments = 
        Array.AsReadOnly segments

    override this.Equals(obj) =
        match obj with
        | :? Path as o -> (this :> IEquatable<_>).Equals(o)
        | _ -> false

    interface IEquatable<Path> with
        member this.Equals(other: Path) =
            Object.ReferenceEquals(this.Segments, other.Segments) ||
            not (isNull this.Segments) && 
            not (isNull other.Segments) &&
            this.Segments.Count = other.Segments.Count &&
            Seq.forall2 PlatformUtils.pathEquals this.Segments other.Segments 

    override this.GetHashCode() =
        let mutable hash = HashCode()

        for i = 0 to this.Segments.Count - 1 do
            PlatformUtils.addPath &hash this.Segments[i]
        hash.ToHashCode()


let set =
    HashSet<Path> [
        Path("C:", "tmp", "file.txt")
        Path("C:", "TMP", "file.txt")
        Path("C:", "tmp", "FILE.TXT") ]

printfn $"Item count: {set.Count}."

// The example displays the following output:
// Item count: 1.

Public Structure Path
    Implements IEquatable(Of Path)

    Public ReadOnly Property Segments As IReadOnlyList(Of String)

    Public Sub New(ParamArray ByVal segments() As String)
        Me.Segments = segments
    End Sub

    Public Overrides Function Equals(obj As Object) As Boolean
        Return (TypeOf obj Is Path) AndAlso Equals(DirectCast(obj, Path))
    End Function

    Public Overloads Function Equals(other As Path) As Boolean Implements IEquatable(Of Path).Equals
        If ReferenceEquals(Segments, other.Segments) Then Return True
        If Segments Is Nothing OrElse other.Segments Is Nothing Then Return False
        If Segments.Count <> other.Segments.Count Then Return False

        For i As Integer = 0 To Segments.Count - 1
            If Not PathEquals(Segments(i), other.Segments(i)) Then Return False
        Next

        Return True
    End Function

    Public Overrides Function GetHashCode() As Integer
        Dim hash As HashCode = New HashCode()

        For i As Integer = 0 To Segments?.Count - 1
            AddPath(hash, Segments(i))
        Next

        Return hash.ToHashCode()
    End Function
    
End Structure

Friend Module PlatformUtils

    Public Function PathEquals(ByVal a As String, ByVal b As String) As Boolean
        Return String.Equals(a, b, StringComparison.OrdinalIgnoreCase)
    End Function

    Public Sub AddPath(ByRef hash As HashCode, ByVal path As String)
        hash.Add(path, StringComparer.OrdinalIgnoreCase)
    End Sub

End Module

Module Program

    Sub Main(args As String())
        Dim hashSet As HashSet(Of Path) = New HashSet(Of Path) From {
            New Path("C:", "tmp", "file.txt"),
            New Path("C:", "TMP", "file.txt"),
            New Path("C:", "tmp", "FILE.TXT")
        }
        Console.WriteLine($"Item count: {hashSet.Count}.")
    End Sub

End Module
' The example displays the following output:
' Item count: 1.

Комментарии

Можно использовать для HashCode объединения нескольких значений (например, полей в структуре или классе) в один хэш-код. Эта структура имеет статические методы и методы экземпляра, которые работают по-разному:

  • Статические методы принимают набор из восьми значений для объединения.
  • Два метода экземпляра работают в режиме потоковой передачи, принимая значения по одному за раз.

Предупреждение

Рекомендуется рассматривать хэш-коды в качестве сведений о реализации, так как реализация может меняться в разных версиях сборки. Не храните хэш-коды, созданные HashCode в сериализованных структурах, например на диске. HashCodeиспользует статически инициализированное случайное начальное значение для применения этой рекомендации. Это означает, что хэш-коды являются детерминированными только в область процесса операционной системы.

Методы

Add<T>(T)

Добавляет одно значение в хэш-код.
Add<T>(T, IEqualityComparer<T>)

Добавляет одно значение в хэш-код, указав тип, который предоставляет функции хэш-кода.
AddBytes(ReadOnlySpan<Byte>)

Добавляет диапазон байтов в хэш-код.
Combine<T1,T2,T3,T4,T5,T6,T7,T8>(T1, T2, T3, T4, T5, T6, T7, T8)

Объединяет восемь значений в хэш-код.
Combine<T1,T2,T3,T4,T5,T6,T7>(T1, T2, T3, T4, T5, T6, T7)

Объединяет семь значений в хэш-код.
Combine<T1,T2,T3,T4,T5,T6>(T1, T2, T3, T4, T5, T6)

Объединяет шесть значений в хэш-код.
Combine<T1,T2,T3,T4,T5>(T1, T2, T3, T4, T5)

Объединяет пять значений в хэш-код.
Combine<T1,T2,T3,T4>(T1, T2, T3, T4)

Объединяет четыре значения в хэш-код.
Combine<T1,T2,T3>(T1, T2, T3)

Объединяет три значения в хэш-код.
Combine<T1,T2>(T1, T2)

Объединяет два значения в хэш-код.
Combine<T1>(T1)

Рассеивает хэш-код, возвращенный указанным значением.
Equals(Object)
Устаревшие..

Этот метод не поддерживается и не должен вызываться.
GetHashCode()
Устаревшие..

Этот метод не поддерживается и не должен вызываться.
ToHashCode()

Вычисляет окончательный хэш-код после последовательных вызовов Add.

Применяется к