Question

I would like to allow some of my SOAP header elements to be nillable. This is possible for body elements, but I am not sure if it is allowed from header elements.

In the sample message below, I would like to allow the MessageDateTime to be null.

<definitions  xmlns="http://schemas.xmlsoap.org/wsdl/"
              xmlns:wsaw="http://www.w3.org/2006/05/addressing/wsdl"
              xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
              xmlns:tns="http://mycompany.com/repositoryservice">
  <types>
    <schema xmlns="http://www.w3.org/2001/XMLSchema"
            attributeFormDefault="qualified"
            elementFormDefault="qualified"
            targetNamespace="http://mycompany.com/repositoryservice">
      <element name="MessageDateTime" type="dateTime" />
      <element name="SaveRequest">
        <!-- complexType -->
      </element>
    </schema>
  </types>
  <message name="SaveRequest_Headers">
    <part name="MessageDateTime" element="tns:MessageDateTime" />
  </message>
  <message name="SaveRequest">
    <part name="parameters" element="tns:SaveRequest" />
  </message>
  <binding name="RepositoryServiceBinding" type="tns:IRepositoryService">
    <soap:binding transport="http://schemas.xmlsoap.org/soap/http" />
    <operation name="Save">
      <soap:operation soapAction="http://mycompany.com/repositoryservice/Save" style="document" />
      <input name="SaveRequest">
        <soap:header message="tns:SaveRequest_Headers" part="MessageDateTime" use="literal" />
        <soap:body use="literal" />
      </input>
    </operation>
  </binding>
  <!-- service, portType -->
</definitions>

Answer 1

It is allowed as long as the definition allows for it. In your case, all you have to do is add the nillable="true" to the element’s definition. The result on .NET w/ WCF would look something like this:

    [System.ServiceModel.MessageHeaderAttribute(Namespace="...")]
    [System.Xml.Serialization.XmlElementAttribute(IsNullable=true)]
    public System.Nullable<System.DateTime> MessageDateTime;