# HashCode 结构

## 定义

``public value class HashCode``
``public struct HashCode``
``type HashCode = struct``
``Public Structure HashCode``

HashCode

## 注解

• 静态方法，这些方法接受一组最多8个要组合的值。Static methods that accept a set of up to eight values to combine.
• 以流式处理方式操作的两个实例方法，一次接受一个值。Two instance methods that operate in a streaming fashion, accepting values one at a time.

### 静态方法Static Methods

``````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.
``````
``````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)
Console.WriteLine(\$"Item count: {hashSet.Count}")
End Sub

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

### 实例方法Instance Methods

``````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++)

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.
``````
``````Public Structure Path
Implements IEquatable(Of Path)

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
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.
``````

``````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++)

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.
``````
``````Public Structure Path
Implements IEquatable(Of Path)

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
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.
``````

HashCode 结构必须按引用传递给其他方法，因为它是值类型。The HashCode structure must be passed by-reference to other methods, as it is a value type.

``````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++)

return hash.ToHashCode();
}
}

internal static class PlatformUtils
{
public static bool PathEquals(string a, string b) => string.Equals(a, b, StringComparison.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.
``````
``````Public Structure Path
Implements IEquatable(Of Path)

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
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)
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.
``````

## 方法

 将单个值添加到哈希代码。Adds a single value to the hash code. 向哈希代码添加单个值，指定提供哈希代码函数的类型。Adds a single value to the hash code, specifying the type that provides the hash code function. 将八个值合并到哈希代码中。Combines eight values into a hash code. 将七个值合并到哈希代码中。Combines seven values into a hash code. 将六个值合并到哈希代码中。Combines six values into a hash code. 将五个值合并到哈希代码中。Combines five values into a hash code. 将四个值合并到哈希代码中。Combines four values into a hash code. 将三个值合并到哈希代码中。Combines three values into a hash code. 将两个值合并到哈希代码中。Combines two values into a hash code. 传播由指定值返回的哈希代码。Diffuses the hash code returned by the specified value. 此方法不受支持，因此不应调用。This method is not supported and should not be called. 此方法不受支持，因此不应调用。This method is not supported and should not be called. 连续调用 Add 后计算最终哈希代码。Calculates the final hash code after consecutive Add invocations.