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POChecking a function result for null values
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  1. POChecking a function result for null values
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    copied!<p>In his answer to <a href="https://stackoverflow.com/questions/9788466/what-is-the-proper-way-to-check-for-null-values">this question</a>, BlackBear suggested replacing </p> <pre><code> string y = Session["key"] == null ? "none" : Session["key"].ToString(); </code></pre> <p>with</p> <pre><code> string y = (Session["key"] ?? "none").ToString(); </code></pre> <p>This works great if <code>Session["key"]</code> is a string value, but what if I want to do this with an object? For example, I could do this:</p> <pre><code> string y = GetMyObject() == null ? "none" : GetMyObject().ToString(); </code></pre> <p>But what if I don't want to evaluate <code>GetMyObject()</code> twice? Is my only choice to store the results in a variable, then check that variable for null?</p> <pre><code> var x = GetMyObject(); string y = (x == null) ? "none" : x.ToString(); </code></pre> <hr> <p>Edit: This is all theoretical - I've run into it before, but I don't have a specific example in front of me right now. That being said, here's an example class.</p> <pre><code>class MyObject { private MyObject() { } public MyObject GetMyObject() { return new MyObject(); } public override string ToString() { return "A String"; } } </code></pre> <p>If I do <code>string y = (GetMyObject() ?? "none").ToString();</code>, I get </p> <blockquote> <p>Operator '??' cannot be applied to operands of type 'MyObject' and 'string'".</p> </blockquote> <p>Ideally, I'd be able to do </p> <pre><code> string y = GetMyObject().ToString() ?? "none"; </code></pre> <p>and have it work even if GetMyObject() is null. Basically null-coalescing operator acting as a self-contained <code>try {} catch (NullReferenceException) {}</code>. I know I <em>can't</em>, but that would be the ideal.</p>
 

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