Question

我已经阅读了许多与C＃中的适当相等有关的文章：

http://www.loganfranken.com/blog/687/overriding-equals-in-c-part-1/

What is the best algorithm for an overridden System.Object.GetHashCode?

假定以下示例类：

public class CustomData
{
    public string Name { get; set;}

    public IList<double> Values = new List<double>();
}

使用 .Equals（）比较 Values 属性是否仍然存在？这是我的意思的完全相等示例：

#region Equality

    public override bool Equals(object value)
    {
        if(Object.ReferenceEquals(null, value)) return false;   // Is null?
        if (Object.ReferenceEquals(this, value)) return true;   // Is the same object?
        if (value.GetType() != this.GetType()) return false;    // Is the same type?

        return IsEqual((CustomData)value);
    }

    public bool Equals(CustomData obj)
    {
        if (Object.ReferenceEquals(null, obj)) return false;    // Is null?
        if (Object.ReferenceEquals(this, obj)) return true;     // Is the same object?

        return IsEqual(obj);
    }

    private bool IsEqual(CustomData obj)
    {
        return obj is CustomData other
            && other.Name.Equals(Name)
            && other.Values.Equals(Values);
    }

    public override int GetHashCode()
    {
        unchecked
        {
            // Choose large primes to avoid hashing collisions
            const int HashingBase = (int) 2166136261;
            const int HashingMultiplier = 16777619;

            int hash = HashingBase;
            hash = (hash * HashingMultiplier) ^ (!Object.ReferenceEquals(null, Name) ? Name.GetHashCode() : 0);
            hash = (hash * HashingMultiplier) ^ (!Object.ReferenceEquals(null, Values) ? Values.GetHashCode() : 0);
            return hash;
        }
    }

    public static bool operator ==(CustomData obj, CustomData other)
    {
        if (Object.ReferenceEquals(obj, other)) return true;
        if (Object.ReferenceEquals(null, obj)) return false;    // Ensure that "obj" isn't null

        return (obj.Equals(other));
    }

    public static bool operator !=(CustomData obj, CustomData other) => !(obj == other);

#endregion

Answer 1

List<T>.Equals(List<T> other)将比较参考。如果要将属性Values的相等性定义为doubles的相同序列，请使用IEnumerable<TSource>.SequenceEqual.(IEnemerable<TSource> other)方法（MSDN）。在下面查看您的IsEqual(CustomData obj)的重构版本：

private bool IsEqual(CustomData obj)
{
    return obj is CustomData other
        && other.Name.Equals(Name)
        && other.Values.SequenceEqual(Values);
}

具有基于列表的属性的C＃相等性

1 个答案: