Web Forms :: System.servicemodel.protocolexception Was Unhandled By User Code

i am using the page asynchronousTask to call the wcf service which is reside in another project in same solution for that i am using following code

protected void Button1_Click(object sender, EventArgs e)
{
PageAsyncTask pat = new PageAsyncTask(BeginDoWork, EndDoWork, null, null);
Page.RegisterAsyncTask(pat);
//Page.ExecuteRegisteredAsyncTasks();
}
IAsyncResult BeginDoWork(object sender, EventArgs e, AsyncCallback acb, object extraData)
{
nor = new ServiceReference1.Service2Client();
return nor.BeginDoWork(acb ,extraData );//first null value is any call back method
//return nor.BeginProductList(acb, extraData);
}
void EndDoWork(IAsyncResult ar)
{
nor.EndDoWork(ar);
}

but in the endDoWork method it will show the following error

system.servicemodel.protocolexception was unhandled by user code