title: Why can't Double be implicitly cast to Decimal
body: <p>I don't understand the casting rules when it comes to decimal and double.</p>
  <p>It is legal to do this</p>
  <pre><code>decimal dec = 10;
  double doub = (double) dec;
  </code></pre>
  <p>What confuses me however is that decimal is a 16 byte datatype and double is 8 bytes so isn't casting a double to a decimal a widening conversation and should therefore be allowed implicitly; with the example above disallowed?</p>
  <pre><code>double doub = 3.2;
  decimal dec = doub; // CS0029: Cannot implicitly convert type 'double' to 'decimal'
  </code></pre>