Patrick,
Thanks for the explanation. I think definately base type is the way to go.
HTH,
Krzysztof
On 14/05/2011 10:50 AM, Patrick van der Velde wrote:
Hi Krzysztof
I forgot about that. There is another method on the CommandProxy class
that is used to raise the event. So the signature of the CommandProxy
class should be more like this:
public class CommandProxy : ICommands
{
public event EventHandler<EventArgs> OnTerminated;
private void RaiseOnAvailabilityChange()
{
var local = OnTerminated;
if (local != null)
{
local(SelfReference(), EventArgs.Empty);
}
}
// Stop the leaking of the 'this' reference by getting it from
this method
// The proxy will override this method and make sure we only
return the
// link to the proxy.
protected internal virtual object SelfReference()
{
return this;
}
public void NotifyOfTermination()
{
RaiseOnAvailabilityChange();
}
}
The NotifyOfTermination method is invoked when the remote interface
disappears (e.g. the remote application signs off from the network or
something). The method is called by casting the proxy to a
commandproxy and then invoking the method, e.g.:
var generator = new ProxyGenerator();
var proxy =
(ICoolCommands)generator.CreateInterfaceProxyWithTarget(
typeof(ICoolCommands),
baseObject,
options,
new IInterceptor[] { selfReference,
methodWithoutResult, methodWithResult });
var commandProxy = (CommandProxy)proxy;
commandProxy.NotifyOfTermination ();
I'll try out the BaseTypeForInterfaceProxies property and see where it
gets me. Would an other solution be to do the following?
var generator = new ProxyGenerator();
var proxy =
(ICoolCommands)generator.CreateInterfaceProxyWithTarget(
typeof(ICommands),
new Type[] { typeof(ICoolCommands) },
baseObject,
options,
new IInterceptor[] { selfReference,
methodWithoutResult, methodWithResult });
I'm not sure what that would do with the overlapping events on the
ICoolCommands interface though.
Regards
Patrick
2011/5/14 Krzysztof Koźmic <[email protected]
<mailto:[email protected]>>
@Patrick,
How and when is RaiseOnAvailabilityChange method invoked?
I'm not sure I got that right but I think what you're really after
is proxy without target, but instead with CommandProxy class as
its base class.
ProxyGenerationOptions has a BaseTypeForInterfaceProxies property
for that.
HTH,
Krzysztof
On 13/05/2011 8:00 AM, Patrick van der Velde wrote:
Hi All
I'm trying to use DynamicProxy to create a proxy object for a
remote interface. For that to work I've done the following. I
have defined a base interface for all command interfaces. This
base interface doesn't provide any command methods but does
provide an event. The base interface looks like this:
public interface ICommands
{
event EventHandler<EventArgs> OnTerminated;
}
That base interface is implemented by a proxy base class which
will be used to refer to the proxy in the storage layer. The
definition of that base proxy object looks like:
public class CommandProxy : ICommands
{
public event EventHandler<EventArgs> OnTerminated;
private void RaiseOnAvailabilityChange()
{
var local = OnTerminated;
if (local != null)
{
local(SelfReference(), EventArgs.Empty);
}
}
// Stop the leaking of the 'this' reference by getting it
from this method
// The proxy will override this method and make sure we
only return the
// link to the proxy.
protected internal virtual object SelfReference()
{
return this;
}
}
Interfaces that derive from ICommands are only allowed to have
methods that either return Task or Task<T> to indicate that any
method called on the interface is likely to take up a finite
amount of time. An example definition of a command interface
looks like this:
public interface ICoolCommands : ICommands
{
Task SomeMethod(int input);
Task<int> SomeOtherMethod(int input);
}
The actual definition of the command interfaces may be different
and is not known to the proxy building code.
I've then defined several interceptors to handle the case of
methods with a Task return value and methods with a Task<T>
return value.
The first interceptor handles (I think) the 'SelfRefence' method
in the base proxy object.
internal sealed class CommandSetProxySelfReferenceInterceptor
: IInterceptor
{
public void Intercept(IInvocation invocation)
{
invocation.ReturnValue = invocation.Proxy;
}
}
The following two interceptors handle the case of methods with a
Task and a Task<T> return value. Note that these interceptors
never call in to the proxy base object because that object
doesn't have any of the correct methods implemented.
internal sealed class
CommandSetMethodWithTaskResultInterceptor : IInterceptor
{
public void Intercept(IInvocation invocation)
{
invocation.ReturnValue =
Task.Factory.StartNew(
() => Console.WriteLine(
string.Format("{}({})",
invocation.Method.Name <http://invocation.Method.Name>,
invocation.Arguments[0])));
}
}
internal sealed class
CommandSetMethodWithTypedTaskResultInterceptor : IInterceptor
{
public void Intercept(IInvocation invocation)
{
invocation.ReturnValue =
Task<int>.Factory.StartNew(
() =>
{
Console.WriteLine(
string.Format("{}({})",
invocation.Method.Name <http://invocation.Method.Name>,
invocation.Arguments[0]));
return 10;
});
}
}
And finally there is an interceptorselector to handle setting up
the interceptor chains.
internal sealed class CommandSetInterceptorSelector :
IInterceptorSelector
{
public IInterceptor[] SelectInterceptors(Type type,
MethodInfo method, IInterceptor[] interceptors)
{
var name = "SelfReference";
if (string.Equals(name, method.Name,
StringComparison.Ordinal))
{
return interceptors.Where(i => i is
CommandSetProxySelfReferenceInterceptor).ToArray();
}
if (method.ReturnType == typeof(Task))
{
return interceptors.Where(i => i is
CommandSetMethodWithTaskResultInterceptor).ToArray();
}
return interceptors.Where(i => i is
CommandSetMethodWithTypedTaskResultInterceptor).ToArray();
}
}
Now to build the proxy I use the following code (simplified from
the real code)
class Program
{
static void Main(string[] args)
{
var baseObject = new CommandProxy();
var selfReference = new
CommandSetProxySelfReferenceInterceptor();
var methodWithoutResult = new
CommandSetMethodWithTaskResultInterceptor();
var methodWithResult = new
CommandSetMethodWithTypedTaskResultInterceptor();
var options = new ProxyGenerationOptions
{
Selector = new CommandSetInterceptorSelector(),
};
var generator = new ProxyGenerator();
var proxy =
(ICoolCommands)generator.CreateInterfaceProxyWithTarget(
typeof(ICoolCommands),
baseObject,
options,
new IInterceptor[] { selfReference,
methodWithoutResult, methodWithResult });
proxy.SomeMethod(10);
var result = proxy.SomeOtherMethod(20);
Console.ReadLine();
}
}
The problem is that it fails when I try to create the proxy (the
line that has generator.CreateInterfaceProxyWithTarget) because
the target doesn't implement the ICoolCommands interface. So the
question now is how can I:
- Create a proxy for a derivative of the ICommands interface,
without the proxy code knowing what that interface is going to be
- Have a base object that I can use to invoke events on
I suspect I want some form of mixin (as shown here
http://kozmic.pl/2009/08/12/castle-dynamic-proxy-tutorial-part-xiii-mix-in-this-mix)
but I'm not sure about that. If anybody has any good suggestions
then that would be awesome.
In case it's necessary I've attached a C# code file with the
example code.
With kind regards
Patrick van der Velde
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