<behaviors>
    <endpointBehaviors>
        <behavior name="...">
            <dataContractSerializer maxItemsInObjectGraph="2147483647"/>
        </behavior>
    </endpointBehaviors>
</behaviors>

<serviceBehaviors>
    <behavior name="...">
        <dataContractSerializer maxItemsInObjectGraph="2147483647" />
    </behavior>
</serviceBehaviors>