title: Nullable type issue with ?: Conditional Operator
body: <p>Could someone explain why this works in C#.NET 2.0:</p>
  
  <pre><code>    Nullable&lt;DateTime&gt; foo;
      if (true)
          foo = null;
      else
          foo = new DateTime(0);
  </code></pre>
  
  <p>...but this doesn't:</p>
  
  <pre><code>    Nullable&lt;DateTime&gt; foo;
      foo = true ? null : new DateTime(0);
  </code></pre>
  
  <p>The latter form gives me an compile error "Type of conditional expression cannot be determined because there is no implicit conversion between '&lt;null&gt;' and 'System.DateTime'."</p>
  
  <p>Not that I can't use the former, but the second style is more consistent with the rest of my code.</p>