.net - 使用对象作为字典键

Question

我想使用以下对象作为字典键。如果分类 和 目标 是平等的，关键是平等的。有什么解决办法吗？

public class TargetKey
{
    public TargetKey(Categories category_arg, String target_arg)
    {
        catetory = category_arg;
        target = target_arg;
    }
    private Categories catetory;
    public Categories Catetory
    {
        get { return catetory; }
        //set { catetory = value; }
    }
    private String target;
    public String Target
    {
        get { return target; }
        //set { target = value; }
    }
}

糟糕的解决方案

好像 GetHashCode()首先调用，如果哈希等于，则 Equals()叫做。
所以我添加了以下两种方法:

    public override bool Equals(object obj)
    {
        TargetKey other = obj as TargetKey;
        return other.Catetory == this.Catetory && other.Target == this.Target;
    }

    public override int GetHashCode()
    {
        return 0;  //this will leads to ONLY 1 bucket, which defeat the idea of Dictionary.
    }

精制方案

    public override bool Equals(object obj)
    {
        TargetKey other = obj as TargetKey;
        return other.Catetory == this.Catetory && other.Target == this.Target;
    }

    public override int GetHashCode()
    {
        Int32 hash = this.Target.GetHashCode() + this.Catetory.GetHashCode(); 
        // This will introduce some more buckets. Though may not be as many as possible.
        return hash;
    }

Answer 1

覆盖和实现 Equals()和 GetHashCode()基于您的类别和目标，这将允许它们作为字典的键用于比较。

这是一个建议的实现，但究竟需要做什么取决于它们是否可以为空。我假设它们可以在下面的实现中，因为构造函数中没有空检查:

public class TargetKey
{
    public TargetKey(Categories category_arg, String target_arg)
    {
        Catetory = category_arg;
        Target = target_arg;
    }
    private Categories catetory;
    public Categories Catetory
    {
        get { return catetory; }
    }
    private String target;
    public String Target
    {
        get { return target; }
    }

    public bool Equals (TargetKey other)
        {
        if (ReferenceEquals (null, other))
            {
            return false;
            }
        if (ReferenceEquals (this, other))
            {
            return true;
            }
        return Equals (other.catetory, catetory) && Equals (other.target, target);
        }

    public override bool Equals (object obj)
        {
        if (ReferenceEquals (null, obj))
            {
            return false;
            }
        if (ReferenceEquals (this, obj))
            {
            return true;
            }
        if (obj.GetType () != typeof (TargetKey))
            {
            return false;
            }
        return Equals ((TargetKey) obj);
        }

    public override int GetHashCode ()
        {
        unchecked
            {
            return ((catetory != null ? catetory.GetHashCode () : 0)*397) ^ (target != null ? target.GetHashCode () : 0);
            }
        }
}