問(wèn)題描述

我需要在對(duì)象和 NULL 之間進(jìn)行比較.當(dāng)對(duì)象不是 NULL 時(shí)，我用一些數(shù)據(jù)填充它.

I need to do a comparaison between an object and NULL. When the object is not NULL I fill it with some data.

代碼如下:

 if (region != null)
 {
  ....
 }

這是有效的，但有時(shí)在循環(huán)和循環(huán)時(shí)，區(qū)域?qū)ο蟛粸榭?我可以在調(diào)試模式下看到其中的數(shù)據(jù)).在調(diào)試時(shí)的逐步調(diào)試中，它不會(huì)進(jìn)入 IF 語(yǔ)句......當(dāng)我使用以下表達(dá)式進(jìn)行快速觀察時(shí):我看到 (region == null) 返回 false, AND (region != null) 也返回 false...為什么以及如何?

This is working but when looping and looping sometime the region object is NOT null (I can see data inside it in debug mode). In step-by-step when debugging, it doesn't go inside the IF statement... When I do a Quick Watch with these following expression : I see the (region == null) return false, AND (region != null) return false too... why and how?

更新

有人指出對(duì)象是 == 和 != 重載:

Someone point out that the object was == and != overloaded:

    public static bool operator ==(Region r1, Region r2)
    {
        if (object.ReferenceEquals(r1, null))
        {
            return false;
        }
        if (object.ReferenceEquals(r2, null))
        {
            return false;
        }

        return (r1.Cmr.CompareTo(r2.Cmr) == 0 && r1.Id == r2.Id);
    }


    public static bool operator !=(Region r1, Region r2)
    {
        if (object.ReferenceEquals(r1, null))
        {
            return false;
        }
        if (object.ReferenceEquals(r2, null))
        {
            return false;
        }
        return (r1.Cmr.CompareTo(r2.Cmr) != 0 || r1.Id != r2.Id);
    }

推薦答案

== 和/或 != 運(yùn)算符是否為區(qū)域?qū)ο蟮念愔剌d?

Is the == and/or != operator overloaded for the region object's class?

既然您已經(jīng)發(fā)布了重載的代碼:

Now that you've posted the code for the overloads:

重載應(yīng)該如下所示(代碼取自 Jon Skeet 和 菲利普·里克):

The overloads should probably look like the following (code taken from postings made by Jon Skeet and Philip Rieck):

public static bool operator ==(Region r1, Region r2)
{
    if (object.ReferenceEquals( r1, r2)) {
        // handles if both are null as well as object identity
        return true;
    }

    if ((object)r1 == null || (object)r2 == null)
    {
       return false;
    }        

    return (r1.Cmr.CompareTo(r2.Cmr) == 0 && r1.Id == r2.Id);
}

public static bool operator !=(Region r1, Region r2)
{
    return !(r1 == r2);
}

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