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POOverriding C# Conditional statements problem
 

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    <p>I was writing some code today and something was not working as I expected.</p> <p>Why does the following code execute even though the condition should have evaluated to false?</p> <p><a href="http://img215.imageshack.us/img215/3011/agfewrf.gif" rel="nofollow noreferrer">alt text http://img215.imageshack.us/img215/3011/agfewrf.gif</a></p> <p>I have tried putting braces around the two conditions, and switching their position, but the EndedUsingApplication even still executes.</p> <p>EDIT:</p> <p>It has nothing to do with the || or &amp;&amp; operators. Look at this...</p> <p><a href="http://img20.imageshack.us/img20/6655/aaaaaal.gif" rel="nofollow noreferrer">alt text http://img20.imageshack.us/img20/6655/aaaaaal.gif</a></p> <p>Nobody can learn from my mistake unless I post the culprit code, so here it is.</p> <pre><code> public static bool operator ==(ActiveApplication a, ActiveApplication b) { if ((object)a == null || (object)b == null) return false; return a.process_name == b.process_name &amp;&amp; a.window_title == b.window_title; } public static bool operator !=(ActiveApplication a, ActiveApplication b) { return a == b ? false : true; } </code></pre> <p>And here is the working code ...</p> <pre><code> public static bool operator ==(ActiveApplication a, ActiveApplication b) { // Casting to object class prevents this comparison operator being executed // again and causing an infinite loop (which I think .NET detects and stops // but it would still be a huge hole in the logic. if ((object)a == null &amp;&amp; (object)b == null) return true; if ((object)a == null ^ (object)b == null) return false; return a.process_name == b.process_name &amp;&amp; a.window_title == b.window_title; } public static bool operator !=(ActiveApplication a, ActiveApplication b) { return a == b ? false : true; } </code></pre> <p>The problem appeared to be when the != operator received two null values.</p>
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    1. COCan you post that code?
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    2. CO@Jay Riggs: Bingo! Yeah it turns out I have. There is some bad logic in there which is returning an incorrect result. Write a proper answer and maybe I'll mark it as the answer ;)
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    3. CO@Nippy - add as an answer! Thanks!
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