title: Is it valid to set nillable=true and use the default property in an XML document?
body: <p>Using C# and .Net 4.0</p>
  
  <p>I have a generated schema that looks like this:</p>
  
  <pre><code>&lt;xsd:element name="EstimatedDate" minOccurs="0" nillable="true" default="1900-01-01T00:00:00"&gt;
    &lt;xsd:complexType&gt;
         &lt;xsd:simpleContent&gt;
             &lt;xsd:extension base="xsd:dateTime"&gt;
                  &lt;xsd:attribute name="origVal" type="xsd:dateTime" use="optional" /&gt;
             &lt;/xsd:extension&gt;
         &lt;/xsd:simpleContent&gt;
    &lt;/xsd:complexType&gt;
  </code></pre>
  
  <p></p>
  
  <p>When I serialize the object with a null value I get:</p>
  
  <pre><code>&lt;EstimatedDate xsi:nil="true" /&gt;
  </code></pre>
  
  <p>But I am getting a deserialization: "There must be no fixed value when an attribute is 'xsi:nil' and has a value of 'true'."</p>
  
  <p>When I look at the XML specification I do not see that nillable and default properties are mutually exclusive, but my other dateTime XML types that are nillable but do not have a default property work correctly.</p>