I developed my code based on this posting :
Asynchronous Programming Model in WCF with async/await
There was no compilation error but when hosted it generates below specified error :
Type 'System.Threading.Tasks.Task`1[System.String]' cannot be serialized. Consid
er marking it with the DataContractAttribute attribute, and marking all of its m
embers you want serialized with the DataMemberAttribute attribute. If the type
is a collection, consider marking it with the CollectionDataContractAttribute.
See the Microsoft .NET Framework documentation for other supported types.
What could be the reason for this.
It looks like one of your methods is either returning a Task object, or has a Task object as one of its parameters.
Tasks cannot be passed across the web-service boundary - this is the cause of your problem.
Update: I had a look at the link you got this code from, and it looks like the code provided is conceptual only. If you look closely at the wording, he says 'will' instead of 'can'.
WCF vNext will adopt the Async model
in both the client and the server
side, and provide new Task-based
overloads for some of the most used
asynchronous APIs.
Since a Task cannot be passed over the web-service boundary, it will not work.
Related
I'm engaged in building NServiceBus Gateway handler, and I need to avoid config files so that all configuration is defined inside c# classes. As a result I have to convert the following section to c# code
<GatewayConfig>
<Channels>
<Channel Address="http://localhost:25899/SiteB/" ChannelType="Http" Default="true"/>
</Channels>
</GatewayConfig>
I've found GatewayConfig, ChannelCollection and ChannelConfig in a NServiceBus.Config namespace, but I can not link them together, coz GatewayConfig refers to ChannelCollection, but ChannelCollection has nothing to do with ChannelConfig. Please help
Just create a class implementing IProvideConfiguration of GatewayConfig. That gives you a way to provide your own config. Look at the pubsub sample for the exact details on how to do this.
Well, I've found the way to do it as I installed Reflector and looked into the implementation. There is a ChannelCollection.CreateNewElement() method returning back System.Configuration.ConfigurationElement. NServiceBus overriden the method instantiating ChannelConfig inside it, so all I have to do is to cast ConfigurationElement type to ChannelConfig type which is far from intuitive interface. Looks like this NServiceBus.Config.ChannelCollection is kind of unfinished work, because if you look at other collections like NServiceBus.Config.MessageEndpointMappingCollection you can find there all necessary type-safe methods to work with its child elements NServiceBus.Config.MessageEndpointMapping, so I think NServiceBus team was just lazy to make the same for ChannelCollection.
UPDATE: as CreateNewElement() method is protected, I have to implement my own class inherited from ChannelCollection to make a method adding new ChannelConfig element publicly available
We need to add a new profiling feature to our WCF application, for logging where time is spendt in the application. I'm looking at PostSharp for a convention driven approach of applying the logging and need some input on how to actually log it. I've already created a custom class for logging purposes, using StopWatch and can log the steps through the layers of my WCF application. However I'm wondering if there's a thread safe alternative library I could use in conjunction with PostSharp for this purpose. I've come across MiniProfiler, but it seems to be intended for ASP.NET MVC applications mainly. Any other frameworks I should consider or should I just use my custom class?
Thanks
I did something like that in the past using a IClientMessageInspector implemented on a custom IEndpointBehavior.
Depending on what kind of logging you want, this might just do the trick. There's an example in the following link
IClientMessageInspector Interface
PostSharp itself is thread-safe. The aspects that you write may be thread-unsafe if poorly written, but there's always a way to make them thread-safe.
If you're using OnMethodBoundaryAspect and need to pass something from OnEntry to OnSuccess, store the initial stopwatch value in OnMethodExecutionArgs.MethodExecutionTag.
I recently moved to using the binary serializer to send messages with NServiceBus. My messages are all defined as interfaces and are instantiated using
bus.Send<MessageType>(msg => msg.Property = someValue)
This leads to an exception being thrown from NServiceBus stating that
Cannot create an instance of an
interface
I can see from the stack trace that the SimpleMessageMapper is being used, and after looking in the source can see it's making a call to Activator.CreateInstance.
I can't find anything in the documentation stating that it's not possible to do what I'm trying to do, is there a way to fix this?
Thanks,
Matt
I only just started playing with nServiceBus, so all I can offer you is theory :).
Are you defining the implementation classes for your message interfaces, or is nServiceBus generating classes on its own? If the former, make sure you still have a default constructor and that the class and all fields/events are marked as [Serializable] or [NonSerialized]. If the latter, it's possible that nServiceBus doesn't know how to generate members which may be needed for (de)serialization. You may have to write and map the implementation class yourself.
I am fairly new to WCF and just have a question on how to correctly get MessageContract inheritance working. A simplified version of my setup is as follows - a "base" message type, and then another "test" message which inherits from it.
[MessageContract]
public abstract class BaseMessage
{ }
[MessageContract]
public class TestMessage : BaseMessage
{ }
I then have an asynchronous OperationContract on a ServiceContract defined as:
[OperationContract(AsyncPattern = true)]
IAsyncResult BeginFindRequest(BaseMessage request, AsyncCallback callback, object asyncState);
The problem that I am getting is when calling the BeginFindRequest method, and passing in a TestMessage instance for the request parameter, the WCF framework is deserialising the TestMessage instance to BaseMessage on the service/server side. As this is defined as an abstract class, it results in the following error:
"The message cannot be deserialized
into MessageContract type BaseMessage
since it does not have a default
(parameterless) constructor."
From the limited information that I can find on MessageContract inheritance, it seems that it should just work.
So my question is - what am I missing in order to get this to work; or should I perhaps rather define a seperate OperationContract on the ServiceContract specifically for that type - the downside being that I could end up with many additional OperationContracts?
In the end I found this blog post which hit the nail on the head -
Unfortunately the way that contracts
are expressed in WCF makes is very
easy to forget what their purpose is:
to define the messages send to the
operation and being sent back from the
operation. In reality you have to
think “how would I express this data
in XML?”. XML doesn’t support
inheritance so whatever you put in the
contract is going to have to have some
way of mapping to XML. The data
contracts used to define the messages
are simply a .NET typed convenience
for generating the XML for the data
you want to pass – if you view them
any other way you are destined for a
world of pain. So think about the data
you want to pass, not how it may
happen to be represented in your
business layer and design your
DataContracts accordingly.
http://www.dotnetconsult.co.uk/weblog2/PermaLink,guid,a3775eb1-b441-43ad-b9f1-e4aaba404235.aspx
So I will be refactoring to provide an additional method with an explicit contract type. This will also allow me to clean up the service implementation by removing all the type checking.
Thanks for the assistance.
OK, first question is: why are you really using Message contracts? Do you really have a need for that??
Typically, message contracts are only ever used when you need to tightly control the layout of your SOAP message, e.g. to satisfy a legacy system you need to call which requires specific headers and such.
A "normal" WCF call should hardly ever need to use a message contract.
You define your service calls (the methods on your service) using [ServiceContract], and the data structures being passed around as [DataContract]. If you have a DataContract, you have more options as to how to deal with inheritance / polymorphism in your service (more than with the message contract construct).
Marc
Is that possible to change BaseMessage so that it is concrete class with parameterless constructor?
The error message tells that there is no way to initialize the object of type BaseMessage because it is abstract.
The error simply wants you to have a default empty contructor that it can use. However, I agree with marc_s; in the projects I've worked on I've rarely used message contract, the only case I can remember was as part of a file transfer service where file chunks were passed in messasges.
Try decorating your [ServiceContract] with the KnownType attribute. Since TestMessage is not 'visible' from a public operation, this helps the plumbing know how to treat it when it sees it.
If this should allow the [DataContract] to be serialized as a TestMessage your still likely to need to handle multiple messages differently via 'is a' or some other casting.
Well I had declared this default (parameterless) constructor for sure, but that was not still working fine for me, for me the issue was, the access modifier was protected while it should be public:
public constructor() { }
^^^^
To implement "method-missing"-semantics and such in C# 4.0, you have to implement IDynamicObject:
public interface IDynamicObject
{
MetaObject GetMetaObject(Expression parameter);
}
As far as I can figure out IDynamicObject is actually part of the DLR, so it is not new. But I have not been able to find much documentation on it.
There are some very simple example implementations out there (f.x. here and here), but could anyone point me to more complete implementations or some real documentation?
Especially, how exactly are you supposed to handle the "parameter"-parameter?
The short answer is that the MetaObject is what's responsible for actually generating the code that will be run at the call site. The mechanism that it uses for this is LINQ expression trees, which have been enhanced in the DLR. So instead of starting with an object, it starts with an expression that represents the object, and ultimately it's going to need to return an expression tree that describes the action to be taken.
When playing with this, please remember that the version of System.Core in the CTP was taken from a snapshot at the end of August. It doesn't correspond very cleanly to any particular beta of IronPython. A number of changes have been made to the DLR since then.
Also, for compatibility with the CLR v2 System.Core, releases of IronPython starting with either beta 4 or beta 5 now rename everything in that's in the System namespace to be in the Microsoft namespace instead.
If you want an end to end sample including source code, resulting in a dynamic object that stores value for arbitrary properties in a Dictionary then my post "A first look at Duck Typing in C# 4.0" could be right for you. I wrote that post to show how dynamic object can be cast to statically typed interfaces. It has a complete working implementation of a Duck that is a IDynamicObject and may acts like a IQuack.
If you need more information contact me on my blog and I will help you along, as good as I can.
I just blogged about how to do this here:
http://mikehadlow.blogspot.com/2008/10/dynamic-dispatch-in-c-40.html
Here is what I have figured out so far:
The Dynamic Language Runtime is currently maintained as part of the IronPython project. So that is the best place to go for information.
The easiest way to implement a class supporting IDynamicObject seems to be to derive from Microsoft.Scripting.Actions.Dynamic and override the relevant methods, for instance the Call-method to implement function call semantics. It looks like Microsoft.Scripting.Actions.Dynamic hasn't been included in the CTP, but the one from IronPython 2.0 looks like it will work.
I am still unclear on the exact meaning of the "parameter"-parameter, but it seems to provide context for the binding of the dynamic-object.
This presentation also provides a lot of information about the DLR:
Deep Dive: Dynamic Languages in Microsoft .NET by Jim Hugunin.