How do I test the state of my proxy before making calls to my WCF service.
I have a duplex channel created using a duplex channel factory.
Before making any calls to the server I want to check the state of the proxy object created from the channel factory.
I saw this in a book... (to be used in immediate window)
? ((ICommunicationObject)flsProxy).State
But it gave this exception...
Cannot obtain fields or call methods on the instance of type 'System.ServiceModel.ICommunicationObject' because it is a proxy to a
remote object.
Is it better to just catch exceptions?
If you create your client proxy using a DuplexChannelFactory<T>, you should get back a regular old WCF channel:
Callbacks myCallbacks = new Callbacks();
DuplexChannelFactory<IMyService> factory =
new DuplexChannelFactory<IMyService>(myCallbacks,
new NetTcpBinding(), new EndpointAddress(.....));
IMyService proxy = factory.CreateChannel();
and you should be able to cast that to a ICommunicationObject and check its state:
ICommunicationObject comobj = (ICommunicationObject)proy;
if(comobj.State != CommunicationState.Faulted)
{
// call the service method
}
Where in this chain of statements does it no longer work for you??
Related
I'm fairly recent to WCF and trying to figure out the best way to accomplish my requirements.
I have an application hosting a WCF service with the following code:
Uri u1 = new
Uri("http://localhost:8732/Client1/WcfServiceLibrary1/Service1/"); Uri
u2 = new
Uri("http://localhost:8732/Client1/WcfServiceLibrary1/Service1/mex");
WSHttpBinding binding = new WSHttpBinding();
sHost = new ServiceHost(typeof(WcfServiceLibrary1.Service1), u1);
ServiceMetadataBehavior meta = new ServiceMetadataBehavior();
meta.HttpGetEnabled = true;
sHost.AddServiceEndpoint(typeof(WcfServiceLibrary1.IService1), binding, u1);
sHost.Description.Behaviors.Add(meta); sHost.Open();
I can create a service reference on a client application and call methods on this service no problems. using the code below.
remoteService.Service1Client client = new remoteService.Service1Client();
remote.Text = client.GetData(3);
I can also call a method without a service reference.
EndpointAddress myEndpoint = new EndpointAddress("http://localhost:8732/Client1/WcfServiceLibrary1/Service1/");
WSHttpBinding myBinding = new WSHttpBinding();
ChannelFactory<IService1> ServiceConnectionFactory = new ChannelFactory<IService1>(myBinding, myEndpoint);
IService1 serviceConnection = ServiceConnectionFactory.CreateChannel();
If I try to execute the same code in the host application it get the error below.
The request channel timed out while waiting for a reply after
00:01:00. Increase the timeout value passed to the call to Request or
increase the SendTimeout value on the Binding. The time allotted to
this operation may have been a portion of a longer timeout.
How can a application consume and use a WCF service that it is currently hosting? Do I need to open the service in a thread of its own?
The idea is for the host to trigger some initialization before clients connect.
I would like to expose discovery endpoints (both TCP and UDP) for my Data Services v3 and enable services to be discoverable from the client and discover them in another application. The main point in the discovery is to get the service endpoint address at the client.
I have tried to adapt the samples that Microsoft have provided for WCF Discovery, but so far I failed to achieve my goal.
I have created a custom Data Service Host Factory on server side:
public class CustomDataServiceHostFactory : System.Data.Services.DataServiceHostFactory
{
protected override System.ServiceModel.ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses)
{
var serviceHost = base.CreateServiceHost(serviceType, baseAddresses);
EndpointDiscoveryBehavior endpointDiscoveryBehavior = new EndpointDiscoveryBehavior();
// Create XML metadata to add to the service endpoint
XElement endpointMetadata = new XElement(
"Root",
new XElement("Information", "This endpoint is Data Service v3!"),
new XElement("Time", System.DateTime.Now.ToString("MM/dd/yyyy HH:mm")));
// Add the XML metadata to the endpoint discovery behavior.
endpointDiscoveryBehavior.Extensions.Add(endpointMetadata);
//may be this is not the safest way to set the behaviour
foreach (var endpoint in serviceHost.Description.Endpoints)
{
endpoint.Behaviors.Add(endpointDiscoveryBehavior);
}
// Make the service discoverable over UDP multicast
serviceHost.Description.Behaviors.Add(new ServiceDiscoveryBehavior());
serviceHost.AddServiceEndpoint(new UdpDiscoveryEndpoint());
return serviceHost;
}
}
On the client side I have tried the following code:
DiscoveryClient discoveryClient = new DiscoveryClient(new UdpDiscoveryEndpoint());
// Find service endpoints
// ServiceReference.DataModel is the generated class for the Data Service client proxy
FindCriteria findCriteria = new FindCriteria(typeof(ServiceReference.DataModel));
findCriteria.Duration = TimeSpan.FromSeconds(30);
FindResponse findResponse = discoveryClient.Find(findCriteria);
// Check to see if endpoints were found & print the XML metadata in them.
if (findResponse.Endpoints.Count > 0)
{
foreach (XElement xElement in findResponse.Endpoints[0].Extensions)
{
Console.WriteLine("Printing Metadata from ServiceEndpoint:");
Console.WriteLine("Endpoint Information: " + xElement.Element("Information").Value);
Console.WriteLine("Endpoint Started at Time: " + xElement.Element("Time").Value);
Console.WriteLine();
}
}
Unfortunately this does not work. I get InvalidOperationException:
Attempted to get contract type for DataModel, but that type is
not a ServiceContract, nor does it inherit a ServiceContract.
If I am heading in the right direction I need a way to express the type for the service contract for the discovery. Too bad I am not sure that it will even work like the normal WCF Discovery...
Please share your ideas or even better - working solutions.
I think exception message is clear enough.
For service discovery You try to use type of your data model, while You must use type of your WCF service implementation - this is different things.
Basically DataServicesV3 service adapter uses your data model and exposes it as a WCF service with it's own service contract.
Look at DataServiceV3 type declaration see that it is implementing some interface, i just don't remember name, in this interface declaration you will find [ServiceContract] and [ServiceOperation] attributes. This is Your SERVICE CONTRACT for all ancestors of DataServiceV3. They use THE SAME contract. Here stands another problem I haven't managed to solve yet - how to make WS-Discovery work with DataServices if they share same contract. You'd better dig in this way.
My client is using one WCF service which is throwing an exception
(EXCEPTION: The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state).
All subsequent calls throwing an same exception.
I read on internet that client need to close()/Abort() channel, this will solve the problem. is it completely right?
Also I am using customer serviceChannel factory provided by service developers. When I create channel it does not show the close and abort methods. So how do I get these close and abort methods when I create custom service channel instance on client side?
Assuming that you have a proxy instance that implements the IClientChannel interface, here is a way (hopefully the right way) to use it.
IClientChannel clientChannel = (IClientChannel)proxy;
bool success = false;
try
{
// do something with the proxy
clientChannel.Close();
success = true;
}
finally
{
if (!success)
{
clientChannel.Abort();
}
}
You may also want to check this. You can wrap your operations using a shared class or function.
I'm using OperationContext.Current.GetCallbackChannel to get a channel to the client that called a WCF service operation.
Do I need to worry about closing / disposing these callback channels or is this taken care of by the framework?
Well, I just tried it myself and it turns out that if you Close & Dispose the callback channel (after casting to IClientChannel) the entire Service channel becomes useless and when called throws a ProtocolException saying:
"This channel can no longer be used to send messages as the output session was auto-closed due to a server-initiated shutdown. Either disable auto-close by setting the DispatchRuntime.AutomaticInputSessionShutdown to false, or consider modifying the shutdown protocol with the remote server."
I assume that this is an unwelcome consequence or side effect of attempting to close & dispose the callback channel, meaning that this should not be done.
In my opinion you should.
The callback mechanism supplies nothing like a higher-level protocol for managing the
connection between the service and the callback endpoint. It is up to the developer to
come up with some application-level protocol or a consistent pattern for managing the
lifecycle of the connection. The service can only call back to the client if the client-side channel is still open, which is typically achieved by not closing the proxy. Keeping the proxy open will also prevent the callback object from being garbage-collected. If the service maintains a reference on a callback endpoint and the client-side proxy is closed or the client application itself is gone, when the service invokes the callback it will get an ObjectDisposedException from the service channel. It is therefore preferable for the client to inform the service when it no longer wishes to receive callbacks or when the client application is shutting down. To that end, you can add an explicit Disconnect() method to the service contract. Since every method call carries the callback reference with it, in the Disconnect() method the service can remove the callback reference from its internal store.
here is an exemple :
class MyService : IServiceContract
{
static List<IServiceContractCallback> m_Callbacks = new List<IServiceContractCallback>();
public void Connect()
{
IServiceContractCallbackcallback = OperationContext.Current.GetCallbackChannel<IServiceContractCallback>();
if(m_Callbacks.Contains(callback) == false)
{
m_Callbacks.Add(callback);
}
}
public void Disconnect()
{
IServiceContractCallback callback = OperationContext.Current.GetCallbackChannel<IServiceContractCallback>();
if(m_Callbacks.Contains(callback))
{
m_Callbacks.Remove(callback);
}
else
{
throw new InvalidOperationException("Cannot find callback");
}
}
In such a way a client can inform the service that the callback is no longer needed. Does it answer your question ?
I'm using the ChannelFactory in WCF to call into a REST service and I want to determine whether the server returned HTTP 200 or 201 in response to a PUT call. Currently, the call succeeds, but I can't determine if my object was created or updated. How can I do this?
WCF is designed for all sorts of channels so this is not a high level object
You can access it though with something like this
factory.Endpoint.Behaviors.Add(new WebHttpBehavior());
IMyContract proxy = factory.CreateChannel();
using (OperationContextScope scope = new OperationContextScope((IContextChannel)proxy)) {
proxy.MyMethod("Some data"));
var responseCode = WebOperationContext.Current.IncomingResponse.StatusCode;
}
((IClientChannel)proxy).Close();
factory.Close();