自托管WCF抛出400 Bad Request而不是WebFaultException

Question

在我自己托管的WCF网络服务中，我有两种方法：

[System.ServiceModel.OperationContract]
[System.ServiceModel.Web.WebGet(UriTemplate = "Auditoria/getProduto/{c}/{emp}")]
string AU_getProduto(string c, string emp);

[System.ServiceModel.OperationContract, WebInvoke(UriTemplate = "Auditoria/setProdutos/")]
string AU_setProdutos(Stream arq);

public string AU_getProduto(string cod, string emp) {
    if (!exist(emp)){  //exist(string e) method returns a boolean indicating 
                       //if that code is found on a database
        FaultCode code = new FaultCode("Erro");
        throw new WebFaultException<string>("Produto não cadastrado.",
                 System.Net.HttpStatusCode.Forbidden);
    }
}

public string AU_setProdutos(Stream json) {
    //parse json, get information. string emp contains the same info as 
    //the method above after parsing
    if (!exist(emp)){
        FaultCode code = new FaultCode("Erro");
        throw new WebFaultException<string>("Produto não cadastrado.",
                              System.Net.HttpStatusCode.Forbidden);
    }
}

当我调用第一个函数AU_getProduto时，我抛出异常，一切都很好。当调用第二个方法AU_setProduto时，我想抛出异常，而不是抛出异常，它会给我＆＃34;（400）Bad Request＆＃34;。我的猜测是WebInvoke与WebGet的工作方式不同，而WCF在某种程度上消耗了我抛出的异常并抛出了自己的异常。以下是我的app.config：

<?xml version="1.0"?>
<configuration>
    <system.serviceModel>
      <bindings>
        <webHttpBinding>
          <binding name="streamedBinding" >
          </binding>
        </webHttpBinding>
      </bindings>
     <services>
       <service name="WebService.RestService" behaviorConfiguration="Default">
         <host>
           <baseAddresses>
           </baseAddresses>
         </host>
         <endpoint name="WebService.RestSevice" address="" bindingConfiguration="streamedBinding" binding="webHttpBinding" behaviorConfiguration="webBehavior" contract="WebService.ICarga">
         </endpoint>
       </service>
     </services>
     <behaviors>
       <endpointBehaviors>
         <behavior name="webBehavior">
           <webHttp />
         </behavior>
       </endpointBehaviors>
       <serviceBehaviors>
         <behavior name="Default">
           <serviceMetadata httpGetEnabled="true"/>
           <dataContractSerializer maxItemsInObjectGraph="2147483647"/>
         </behavior>
       </serviceBehaviors>
     </behaviors>
   </system.serviceModel>
   <startup>
     <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
   </startup>
</configuration>

那我怎么能抛出预期的异常？

提前致谢。

编辑：

我尝试删除抛出异常的部分，第二种方法可以根据需要运行。因此唯一的问题是抛出异常。