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copied!<p>Because you're using dynamic as the argument to <code>CreateCommand()</code>, the <code>cmd</code> variable is also dynamic, which means its type is resolved at runtime to be <code>SqlCommand</code>. By contrast, the <code>conn</code> variable is not dynamic and is compiled to be of type <code>DbConnection</code>.</p> <p>Basically, <code>SqlCommand.Connection</code> is of type <code>SqlConnection</code>, so the <code>conn</code> variable, which is of type <code>DbConnection</code>, is an invalid value to set <code>Connection</code> to. You can fix this by either casting <code>conn</code> to an <code>SqlConnection</code>, or making the <code>conn</code> variable <code>dynamic</code>.</p> <p>The reason it worked fine before was because <code>cmd</code> was actually a <code>DbCommand</code> variable (even so it pointed to the same object), and the <code>DbCommand.Connection</code> property is of type <code>DbConnection</code>. i.e. the <code>SqlCommand</code> class has a <code>new</code> definition of the <code>Connection</code> property.</p> <p><strong>Source issues annotated:</strong></p> <pre><code> public static dynamic DynamicWeirdness() { dynamic ex = new ExpandoObject(); ex.TableName = "Products"; using (var conn = OpenConnection()) { //'conn' is statically typed to 'DBConnection' var cmd = CreateCommand(ex); //because 'ex' is dynamic 'cmd' is dynamic cmd.Connection = conn; /* 'cmd.Connection = conn' is bound at runtime and the runtime signature of Connection takes a SqlConnection value. You can't assign a statically defined DBConnection to a SqlConnection without cast. */ } Console.WriteLine("It will never get here!"); Console.Read(); return null; } </code></pre> <p><strong>Options for fixing source (pick only 1):</strong></p> <ol> <li><p>Cast to statically declare <code>conn</code> as a SqlConnection: <code>using (var conn = (SqlConnection) OpenConnection())</code></p></li> <li><p>Use runtime type of <code>conn</code>: <code>using (dynamic conn = OpenConnection())</code></p></li> <li><p>Don't dynamic bind CreateCommand: <code>var cmd = CreateCommand((object)ex);</code></p></li> <li><p>Statically define <code>cmd</code>: <code>DBCommand cmd = CreateCommand(ex);</code></p></li> </ol>

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