title: Is the DataMember IsRequired attribute in combination with a Nullable type contradictory?
body: <p>I came across this today in a WCF contract:</p>
  
  <pre><code>[DataMember(IsRequired = true)]
  public DateTime? LastModified { get; set; } 
  </code></pre>
  
  <p>What are the consequences of <code>IsRequired = True</code> and a nullable <code>DateTime</code>? They appear to be contradictory to each other.</p>