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POC# 4: Dynamic and Nullable<>
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  1. POC# 4: Dynamic and Nullable<>
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    copied!<p>So I've got some code that passes around this anonymous object between methods:</p> <pre><code>var promo = new { Text = promo.Value, StartDate = (startDate == null) ? new Nullable&lt;DateTime&gt;() : new Nullable&lt;DateTime&gt;(DateTime.Parse(startDate.Value)), EndDate = (endDate == null) ? new Nullable&lt;DateTime&gt;() : new Nullable&lt;DateTime&gt;(DateTime.Parse(endDate.Value)) }; </code></pre> <p>Methods that receive this anonymous object type declare its type as <code>dynamic</code>:</p> <pre><code>private static bool IsPromoActive(dynamic promo) { return /* check StartDate, EndDate */ } </code></pre> <p>At run-time, however, if <code>StartDate</code> or <code>EndDate</code> are set to <code>new Nullable&lt;DateTime&gt;(DateTime.Parse(...))</code>, a method that receives this <code>dynamic</code> object (named <code>promo</code>) performs this:</p> <pre><code>if (promo.StartDate.HasValue &amp;&amp; promo.StartDate &gt; DateTime.Today || promo.EndDate.HasValue &amp;&amp; promo.EndDate &lt; DateTime.Today) { return; } </code></pre> <p>It throws an exception:</p> <pre><code>Server Error in '/' Application. 'System.DateTime' does not contain a definition for 'HasValue' </code></pre> <p>What's going on here? What don't I understand about <code>Nullable</code> types and the <code>dynamic</code> keyword?</p> <p>This code worked fine before I changed I removed the <code>struct</code> that previously stored <code>Text</code>, <code>StartDate</code>, and <code>EndDate</code> and replaced it with an anonymous type and passed it around as <code>dynamic</code>.</p>
 

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