C# – the best workaround for the WCF client `using` block issue

cusingvb.netwcfwcf-client

I like instantiating my WCF service clients within a using block as it's pretty much the standard way to use resources that implement IDisposable:

using (var client = new SomeWCFServiceClient()) 
{
    //Do something with the client 
}

But, as noted in this MSDN article, wrapping a WCF client in a using block could mask any errors that result in the client being left in a faulted state (like a timeout or communication problem). Long story short, when Dispose() is called, the client's Close() method fires, but throws an error because it's in a faulted state. The original exception is then masked by the second exception. Not good.

The suggested workaround in the MSDN article is to completely avoid using a using block, and to instead instantiate your clients and use them something like this:

try
{
    ...
    client.Close();
}
catch (CommunicationException e)
{
    ...
    client.Abort();
}
catch (TimeoutException e)
{
    ...
    client.Abort();
}
catch (Exception e)
{
    ...
    client.Abort();
    throw;
}

Compared to the using block, I think that's ugly. And a lot of code to write each time you need a client.

Luckily, I found a few other workarounds, such as this one on the (now defunct) IServiceOriented blog. You start with:

public delegate void UseServiceDelegate<T>(T proxy); 

public static class Service<T> 
{ 
    public static ChannelFactory<T> _channelFactory = new ChannelFactory<T>(""); 
    
    public static void Use(UseServiceDelegate<T> codeBlock) 
    { 
        IClientChannel proxy = (IClientChannel)_channelFactory.CreateChannel(); 
        bool success = false; 
        try 
        { 
            codeBlock((T)proxy); 
            proxy.Close(); 
            success = true; 
        } 
        finally 
        { 
            if (!success) 
            { 
                proxy.Abort(); 
            } 
        } 
     } 
}

Which then allows:

Service<IOrderService>.Use(orderService => 
{ 
    orderService.PlaceOrder(request); 
});

That's not bad, but I don't think it's as expressive and easily understandable as the using block.

The workaround I'm currently trying to use I first read about on blog.davidbarret.net. Basically, you override the client's Dispose() method wherever you use it. Something like:

public partial class SomeWCFServiceClient : IDisposable
{
    void IDisposable.Dispose() 
    {
        if (this.State == CommunicationState.Faulted) 
        {
            this.Abort();
        } 
        else 
        {
            this.Close();
        }
    }
}

This appears to be able to allow the using block again without the danger of masking a faulted state exception.

So, are there any other gotchas I have to look out for using these workarounds? Has anybody come up with anything better?

Best Answer

Actually, although I blogged (see Luke's answer), I think this is better than my IDisposable wrapper. Typical code:

Service<IOrderService>.Use(orderService=>
{
  orderService.PlaceOrder(request);
});

(edit per comments)

Since Use returns void, the easiest way to handle return values is via a captured variable:

int newOrderId = 0; // need a value for definite assignment
Service<IOrderService>.Use(orderService=>
  {
    newOrderId = orderService.PlaceOrder(request);
  });
Console.WriteLine(newOrderId); // should be updated
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