HashCode Estructura

  • Referencia

Definición

Espacio de nombres:
System
Ensamblado:
System.Runtime.dll
Ensamblado:
Microsoft.Bcl.HashCode.dll
Ensamblado:
netstandard.dll
Paquete:
Microsoft.Bcl.HashCode v1.1.1
Source:
HashCode.cs
Source:
HashCode.cs
Source:
HashCode.cs

Combina el código hash de varios valores en un código hash único.

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

Ejemplos

Los métodos estáticos de esta clase combinan los códigos hash predeterminados de hasta ocho valores.

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.

Importante

ToHashCode() se debe llamar como máximo una vez por instancia de HashCode.

Los métodos de instancia de esta clase combinan los códigos hash de más de ocho valores.

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.

Los métodos de instancia también combinan los códigos hash generados por una implementación específica 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.

La HashCode estructura debe pasarse por referencia a otros métodos, ya que es un tipo de valor.

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.

Comentarios

Puede usar HashCode para combinar varios valores (por ejemplo, campos en una estructura o clase) en un único código hash. Esta estructura tiene métodos estáticos e de instancia que funcionan de forma diferente:

  • Los métodos estáticos aceptan un conjunto de hasta ocho valores que se van a combinar.
  • Dos métodos de instancia funcionan de forma de streaming, aceptando valores de uno en uno.

Advertencia

Se recomienda considerar los códigos hash como detalles de implementación, ya que la implementación puede cambiar entre versiones de ensamblado. No almacene códigos hash generados por HashCode en estructuras serializadas, por ejemplo, en disco. HashCode usa una inicialización aleatoria inicializada estáticamente para aplicar este procedimiento recomendado, lo que significa que los códigos hash solo son deterministas dentro del ámbito de un proceso de sistema operativo.

Métodos

Add<T>(T)

Agrega un valor único al código hash.
Add<T>(T, IEqualityComparer<T>)

Agrega un valor único al código hash al especificar el tipo que proporciona la función de código hash.
AddBytes(ReadOnlySpan<Byte>)

Agrega un intervalo de bytes al código hash.
Combine<T1,T2,T3,T4,T5,T6,T7,T8>(T1, T2, T3, T4, T5, T6, T7, T8)

Combina ocho valores en un código hash.
Combine<T1,T2,T3,T4,T5,T6,T7>(T1, T2, T3, T4, T5, T6, T7)

Combina siete valores en un código hash.
Combine<T1,T2,T3,T4,T5,T6>(T1, T2, T3, T4, T5, T6)

Combina seis valores en un código hash.
Combine<T1,T2,T3,T4,T5>(T1, T2, T3, T4, T5)

Combina cinco valores en un código hash.
Combine<T1,T2,T3,T4>(T1, T2, T3, T4)

Combina cuatro valores en un código hash.
Combine<T1,T2,T3>(T1, T2, T3)

Combina tres valores en un código hash.
Combine<T1,T2>(T1, T2)

Combina dos valores en un código hash.
Combine<T1>(T1)

Difunde el código hash devuelto por el valor especificado.
Equals(Object)
Obsoletos.

Este método no se admite y no se debe llamar.
GetHashCode()
Obsoletos.

Este método no se admite y no se debe llamar.
ToHashCode()

Calcula el código hash final después de invocaciones de Add consecutivas.

Se aplica a