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POC# ADO.NET: nulls and DbNull -- is there more efficient syntax?
 

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    <p>I've got a <code>DateTime?</code> that I'm trying to insert into a field using a <code>DbParameter</code>. I'm creating the parameter like so:</p> <pre><code>DbParameter datePrm = updateStmt.CreateParameter(); datePrm.ParameterName = "@change_date"; </code></pre> <p>And then I want to put the value of the <code>DateTime?</code> into the <code>dataPrm.Value</code> while accounting for <code>null</code>s.</p> <p>I thought initially I'd be clever:</p> <pre><code>datePrm.Value = nullableDate ?? DBNull.Value; </code></pre> <p>but that fails with the error</p> <blockquote> <p>Operator '??' cannot be applied to operands of type 'System.DateTime?' and 'System.DBNull'</p> </blockquote> <p>So I guess that only works if the second argument is a non-nullable version of the first argument. So then I went for:</p> <pre><code>datePrm.Value = nullableDate.HasValue ? nullableDate.Value : DBNull.Value; </code></pre> <p>but that doesn't work either:</p> <blockquote> <p>Type of conditional expression cannot be determined because there is no implicit conversion between 'System.DateTime' and 'System.DBNull'</p> </blockquote> <p>But I don't want to convert between those types!</p> <p>So far the only thing I can get to work is:</p> <pre><code>if (nullableDate.HasValue) datePrm.Value = nullableDate.Value; else datePrm.Value = DBNull.Value; </code></pre> <p>Is that really the only way I can write this? Is there a way to get a one-liner using the ternary operator to work?</p> <p><strong>Update:</strong> I don't really get why the ?? version doesn't work. MSDN says:</p> <blockquote> <p>The ?? operator returns the left-hand operand if it is not null, or else it returns the right operand.</p> </blockquote> <p>That's exactly what I want!</p> <p><strong>Update2:</strong> Well it was kind of obvious in the end:</p> <pre><code>datePrm.Value = nullableDate ?? (object)DBNull.Value; </code></pre>
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    1. COhttp://stackoverflow.com/questions/1545711/is-it-possible-to-coalesce-string-and-dbnull-in-c
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