WCF 中，出现The remote server returned an unexpected response: (400) Bad Request.

服务器端配置

<bindings>

      <wsDualHttpBinding>
        <binding name="SubscribeBindingConfig" receiveTimeout="23:59:59" messageEncoding="Text"
          bypassProxyOnLocal="true" useDefaultWebProxy="false" maxBufferPoolSize="4000000" maxReceivedMessageSize="4000000" >
          <reliableSession inactivityTimeout="23:59:59" />
          <readerQuotas maxDepth="64" maxStringContentLength="16384" maxArrayLength="16384"
                        maxBytesPerRead="8192" maxNameTableCharCount="16384" />
        </binding>
      </wsDualHttpBinding>

    </bindings>

客户端配置：

  <bindings>
            <basicHttpBinding>
                <binding name="BasicHttpBinding_IPublishService" closeTimeout="00:01:00"
                    openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"
                    allowCookies="false" bypassProxyOnLocal="true" useDefaultWebProxy="false" hostNameComparisonMode="StrongWildcard"
                    maxBufferSize="171072" maxBufferPoolSize="1524288" maxReceivedMessageSize="171072"
                    messageEncoding="Text" textEncoding="utf-8" transferMode="Buffered">
                    <readerQuotas maxDepth="64" maxStringContentLength="16384" maxArrayLength="16384"
                        maxBytesPerRead="8192" maxNameTableCharCount="16384" />                    
                    <security mode="None">
                        <transport clientCredentialType="None" proxyCredentialType="None"
                            realm="" />
                        <message clientCredentialType="UserName" algorithmSuite="Default" />
                    </security>
                </binding>
            </basicHttpBinding>
        </bindings>
        <client>
          <endpoint address="http://localhost:8734/Design_Time_Addresses/MessageBroker.Framework/PublishService/"
                binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_IPublishService"
                contract="IPublishService" name="BasicHttpBinding_IPublishService" />

        </client>

客户端代码：

PublishServiceClient client = new PublishServiceClient();
            
            MessageDoc doc = new MessageDoc();
            doc.SendSubject = TxSubject.Text.Trim();
            doc.Add("MachineName", Environment.MachineName);
            ..............

            client.Send(doc);      

如果上述中的Add 的数据量大，Send就会报告The remote server returned an unexpected response: (400) Bad Request.

不知道什么原因，各种绑定参数都做过改动，都无济于事。

请高手帮忙！