Pass interface methods as parameters

Note : This is most likely a very C#specific language issue that has nothing to do with it WCFor web servicesnot at all.

There is a 3rd party ASMXweb service which should be used for data retrieval. I created a generic method called ExecuteCommand(), which is used for every request made to the web service. The purpose of this method is to handle cookie sessions/exceptions and other common logic. For each request, a new channel should be used to simplify disposal of unused resources.

The problem is with that ExecuteCommand()method - I have to initialize a channel each time to be able to pass the method to be executed as a parameter. Sorry it sounds too complicated. Here is a usage example:

string color = "blue";
var channel = _strategyFactory.CreateChannel<CarServiceSoapChannel>();
var cars = WcfHelper.ExecuteCommand(channel, () => channel.GetCars(color));
// channel is null here. Channel was closed/aborted, depending on Exception type.

After that ExecuteCommand()is called - channelhas been disposed of. The reason an channelobject is needed at all is to be able to provide a method that can be executed as a parameter! ie () => channel.GetCars(). To further support these words, here is WcfHelperthe inside of the class:

public static class WcfHelper
{
    public static Cookie Cookie { get; set; }

    public static T ExecuteCommand<T>(IClientChannel channel, Expression<Func<T>> method)
    {
        T result = default(T);

        try
        {
            // init operation context
            using (new OperationContextScope(channel))
            {
                // set the session cookie to header
                if (Cookie != null) {
                    HttpRequestMessageProperty request = new HttpRequestMessageProperty();
                    request.Headers["Cookie"] = cookie.ToString();
                    OperationContext.Current.OutgoingMessageProperties[HttpRequestMessageProperty.Name] = request;  
                }

                // execute method
                var compiledMethod = method.Compile();
                result = compiledMethod.Invoke();
            }
        }
        // do different logic for FaultException, CommunicationException, TimeoutException
        catch (Exception)
        {
            throw;
        }
        finally
        {
            CloseOrAbortServiceChannel(channel);
            channel = null;
        }

        return result;
    }

    private static void CloseOrAbortServiceChannel(ICommunicationObject communicationObject)
    {
        bool isClosed = false;

        if (communicationObject == null || communicationObject.State == CommunicationState.Closed)
            return;

        try
        {
            if (communicationObject.State != CommunicationState.Faulted)
            {
                communicationObject.Close();
                isClosed = true;
            }
        }
        catch (Exception)
        {
            throw;
        }
        finally
        {
            if (!isClosed)
                AbortServiceChannel(communicationObject);
        }
    }

    private static void AbortServiceChannel(ICommunicationObject communicationObject)
    {
        try
        {
            communicationObject.Abort();
        }
        catch (Exception)
        {
            throw;
        }
    }
}

So, short question - is it possible to initialize variables inside channelthe ExecuteCommandmethod itself , while at the same time it is possible to define which method should be executed inside ExecuteCommandfor a given channel ?

I am trying to accomplish something like this:

string color = "blue";
var cars = WcfHelper.ExecuteCommand<Car[], CarServiceSoapChannel>(channel => channel.GetCars(color));

even

string color = "blue";
var cars = WcfHelper.ExecuteCommand<CarServiceSoapChannel>(channel => channel.GetCars(color));

Of course, any other code improvement suggestions are welcome, but not mandatory.

PS is added ASMXas Service referencein Visual Studio. So there are some entities that are auto-generated for "CarService" like - CarServiceSoapChannelinterfaces, CarServiceSoapClientclasses, and of course interfaces that CarServicecontain web service methods. In the above example, a ChannelFactoryis used to create a channel for the CarServiceSoapChannelinterface , so here the question name comes from: Passing an interface method as a parameter. This can be misleading, but I hope it's pretty clear what's being accomplished from the description itself.

Update 25.05.2018 I followed @nvoigt 's suggestion and was able to achieve my desired result:

public static TResult ExecuteCommand<TInterface, TResult>(Func<TInterface, TResult> method)
    where TInterface : IClientChannel
{
    TResult result = default(TResult);
    IClientChannel channel = null;

    try
    {
        channel = StrategyFactory.CreateChannel<TInterface>();

        // init operation context
        using (new OperationContextScope(channel))
        {
            // set the session cookie to header
            if (Cookie != null)
                Cookie.SetCookieForSession();

            // execute method
            result = method((TInterface)channel);
        }
    }
    catch (Exception)
    {
        throw;
    }
    finally
    {
        CloseOrAbortServiceChannel(channel);
        channel = null;
    }

    return result;
}

This has achieved the original goal. However, there is a problem with this approach. In order to call the method - you have to explicitly specify the return parameter of the method.

If you're going to call the method, so to speak - it's not enough to write code:

var result = WcfHelper.ExecuteCommand<CarServiceSoapChannel>(channel => channel.IsBlue())

You will have to specify the return type asboolean

var result = WcfHelper.ExecuteCommand<CarServiceSoapChannel, bool>(channel => channel.IsBlue())

I personally don't mind writing extra code as it still has a big advantage over my initial method implementation, however, I'm wondering if the new version can improve this?

For example, when I have only 1 generic type TResultin the method - the return type <TResult>can be omitted. This is no longer the case with 2 generics. Anyway, thanks @nvoigt !