title: Assign a DateTime to Nullable<DateTime> in F#
body: <p>I have some F# code where I need to update a field in a database record. I am using the Type Provider for SQL.  The table has a nullable datevalue field.  When I try to update the value of the date field to DateTime.UtcNow the compiler complains that "This expression was expected to have type Nullable&lt;DateTime> but here has type DateTime".  How do I convert/cast from DateTime to Nullable&lt;DateTime>.</p>
  
  <p>My code currently looks something like follows:</p>
  
  <pre><code>for queryItem in queryResult do
      queryItem.CurrentDate &lt;-  DateTime.UtcNow  // This gives compiler error as described above
  </code></pre>
  
  <p>Regards</p>