title: bind silverlight dataform
body: <p>Hello guys i have dataform in silverlight 4 project item source is:</p>
  
  <pre><code>ItemsSource="{Binding Data, ElementName=domainDataSource1, Mode=TwoWay}"
  </code></pre>
  
  <p>and domain data source is :</p>
  
  <pre><code>&lt;riaControls:DomainDataSource Name="domainDataSource1" QueryName="GetCarsQuery"  AutoLoad="True"&gt;
          &lt;riaControls:DomainDataSource.DomainContext&gt;
              &lt;domain:DataDomainContext/&gt;
          &lt;/riaControls:DomainDataSource.DomainContext&gt;
      &lt;/riaControls:DomainDataSource&gt;
  </code></pre>
  
  <p>My cars table have relationship with trailers table. I have combobox on my data form where i want to show all trailers marks how i can bind combobox another query?
  And when user will save data how i can get trailers id with mark? </p>
  
  <p>thanks</p>