How to make sure you don't get WCF Faulted state exception?

Question

I am getting this exception:

The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state.

The WCF service uses the default wsHttpBinding. I am using WCF in the following way wherever I am using it:

using (var proxy = new CAGDashboardServiceClient())
{
    proxy.Open();
    var result = proxy.GetSiteForRegion(ddlRegions.SelectedValue);
    ddlSites.DataSource = result;
    ddlSites.DataBind();
    proxy.Close();
}

The error line shown in the message seems to be after last proxy.close. Not sure what is going on. I am launching the service from within visual studio 08.

Here is the trace information:

The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state.

Server stack trace: 
  at System.ServiceModel.Channels.CommunicationObject.Close(TimeSpan timeout)

Exception rethrown at [0]: 
  at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
  at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
  at System.ServiceModel.ICommunicationObject.Close(TimeSpan timeout)
  at System.ServiceModel.ClientBase`1.System.ServiceModel.ICommunicationObject.Close(TimeSpan timeout)
  at System.ServiceModel.ClientBase`1.Close()
  at System.ServiceModel.ClientBase`1.System.IDisposable.Dispose()
  at CAGDashboard.UserControls.ucVolunteerCRUDGrid.ddlRegions_SelectedIndexChanged(Object sender, EventArgs e) in C:\Documents and Settings\rballalx\My Documents\Visual Studio 2008\Projects\DashboardCAG\CAGDashboard\UserControls\ucVolunteerCRUDGrid.ascx.cs:line 81
  at System.Web.UI.WebControls.ListControl.OnSelectedIndexChanged(EventArgs e)
  at System.Web.UI.WebControls.DropDownList.RaisePostDataChangedEvent()
  at System.Web.UI.WebControls.DropDownList.System.Web.UI.IPostBackDataHandler.RaisePostDataChangedEvent()
  at System.Web.UI.Page.RaiseChangedEvents()
  at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Answer 1

You should avoid putting client proxies in using blocks.