HashCode Struktur

Definisi

Ruang nama:

System

Rakitan:

System.Runtime.dll

Sumber:

HashCode.cs

Menggabungkan kode hash untuk beberapa nilai ke dalam satu kode hash.

public value class HashCode

public struct HashCode

type HashCode = struct

Public Structure HashCode

Warisan

Object

ValueType

HashCode

Contoh

Metode statis di kelas ini menggabungkan kode hash default hingga delapan nilai.

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.

Penting

ToHashCode() harus dipanggil paling banyak sekali per instans HashCode.

Metode instans di kelas ini menggabungkan kode hash lebih dari delapan nilai.

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.

Metode instans juga menggabungkan kode hash yang dihasilkan oleh implementasi tertentu IEqualityComparer<T> .

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.

Struktur HashCode harus diteruskan dengan referensi ke metode lain, karena merupakan jenis nilai.

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.

Keterangan

Anda dapat menggunakan HashCode untuk menggabungkan beberapa nilai (misalnya, bidang pada struktur atau kelas) ke dalam satu kode hash. Struktur ini memiliki metode statis dan instans yang beroperasi secara berbeda:

• Metode statis menerima satu set hingga delapan nilai untuk digabungkan.
• Dua metode instans beroperasi dengan cara streaming, menerima nilai satu per satu.

Peringatan

Ini adalah praktik terbaik untuk mempertimbangkan kode hash sebagai detail implementasi, karena implementasinya dapat berubah di seluruh versi perakitan. Jangan menyimpan kode hash yang dihasilkan oleh HashCode dalam struktur berseri, misalnya, on-disk. HashCode menggunakan benih acak yang diinisialisasi secara statis untuk memberlakukan praktik terbaik ini, yang berarti bahwa kode hash hanya deterministik dalam cakupan proses sistem operasi.

Metode

Add<T>(T)	Menambahkan satu nilai ke kode hash.
Add<T>(T, IEqualityComparer<T>)	Menambahkan satu nilai ke kode hash, menentukan jenis yang menyediakan fungsi kode hash.
AddBytes(ReadOnlySpan<Byte>)	Menambahkan rentang byte ke kode hash.
Combine<T1,T2,T3,T4,T5,T6,T7,T8>(T1, T2, T3, T4, T5, T6, T7, T8)	Menggabungkan delapan nilai ke dalam kode hash.
Combine<T1,T2,T3,T4,T5,T6,T7>(T1, T2, T3, T4, T5, T6, T7)	Menggabungkan tujuh nilai ke dalam kode hash.
Combine<T1,T2,T3,T4,T5,T6>(T1, T2, T3, T4, T5, T6)	Menggabungkan enam nilai ke dalam kode hash.
Combine<T1,T2,T3,T4,T5>(T1, T2, T3, T4, T5)	Menggabungkan lima nilai ke dalam kode hash.
Combine<T1,T2,T3,T4>(T1, T2, T3, T4)	Menggabungkan empat nilai ke dalam kode hash.
Combine<T1,T2,T3>(T1, T2, T3)	Menggabungkan tiga nilai ke dalam kode hash.
Combine<T1,T2>(T1, T2)	Menggabungkan dua nilai ke dalam kode hash.
Combine<T1>(T1)	Mendifusikan kode hash yang dikembalikan oleh nilai yang ditentukan.
Equals(Object)	Kedaluwarsa. Metode ini tidak didukung dan tidak boleh dipanggil.
GetHashCode()	Kedaluwarsa. Metode ini tidak didukung dan tidak boleh dipanggil.
ToHashCode()	Menghitung kode hash akhir setelah pemanggilan berturut-turut Add .