的IEqualityComparer＆LT; T＆GT;使用的ReferenceEquals

问题描述：

有一个默认的IEqualityComparer的实现，它使用的ReferenceEquals？

Is there a default IEqualityComparer implementation that uses ReferenceEquals?

EqualityComparer＆LT; T＆GT; .DEFAULT 使用ObjectComparer，它使用的Object.Equals（）。就我而言，对象已经实现了IEquatable，我需要忽略和只对象的引用进行比较。

EqualityComparer<T>.Default uses ObjectComparer, which uses object.Equals(). In my case, the objects already implement IEquatable, which I need to ignore and compare by object's reference only.

谢谢！

答

以防万一没有默认的实现，这是我自己的：

Just in case there is no default implementation, this is my own:

编辑由280Z28：为什么要使用RuntimeHelpers.GetHash$c$c(object)$c$c>,其中有许多你可能以前从未见过的。 :)这个方法有两个作用，使其在正确的呼吁，这个实现：

Edit by 280Z28: Rationale for using RuntimeHelpers.GetHashCode(object), which many of you probably haven't seen before. :) This method has two effects that make it the correct call for this implementation:

在它返回0，当对象为空。由于的ReferenceEquals 适用于空参数，所以应该比较器的实施GetHash code（）。
在它调用 Object.GetHash code（） 非虚拟化。 的ReferenceEquals 具体忽略）的任何覆盖等于，所以GetHash code（实施中应使用特殊的方法相匹配的ReferenceEquals的效果，而这正是RuntimeHelpers.GetHash code是。

It returns 0 when the object is null. Since ReferenceEquals works for null parameters, so should the comparer's implementation of GetHashCode().
It calls Object.GetHashCode() non-virtually. ReferenceEquals specifically ignores any overrides of Equals, so the implementation of GetHashCode() should use a special method that matches the effect of ReferenceEquals, which is exactly what RuntimeHelpers.GetHashCode is for.

[结束280Z28]

[end 280Z28]

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;

/// <summary>
/// A generic object comparerer that would only use object's reference, 
/// ignoring any <see cref="IEquatable{T}"/> or <see cref="object.Equals(object)"/>  overrides.
/// </summary>
public class ObjectReferenceEqualityComparer<T> : EqualityComparer<T>
    where T : class
{
    private static IEqualityComparer<T> _defaultComparer;

    public new static IEqualityComparer<T> Default
    {
        get { return _defaultComparer ?? (_defaultComparer = new ObjectReferenceEqualityComparer<T>()); }
    }

    #region IEqualityComparer<T> Members

    public override bool Equals(T x, T y)
    {
        return ReferenceEquals(x, y);
    }

    public override int GetHashCode(T obj)
    {
        return RuntimeHelpers.GetHashCode(obj);
    }

    #endregion
}

的IEqualityComparer＆LT; T＆GT;使用的ReferenceEquals

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