WCF异步调用的同步包装

Question

We are calling WCF services asyncronously.

public partial class ServiceClient : System.ServiceModel.ClientBase<MyService>, MyService 
{
    ......
}

ServiceClient _serviceclient;
void Getproducts(string filter, string augument, EventHandler<GetCompletedEventArgs> callback)
{
    _serviceclient.GetAsyncGetproducts(filter, argument, callback);
}

I want to the Getproducts function to be synchronous. What is the best way to achieve this like the following

void Getproducts(string filter, string augument, EventHandler<GetCompletedEventArgs> callback)
{
    _serviceclient.GetAsyncGetproducts(filter, argument, callback);
    //wait until callback comes back and return
}

EDIT: The proxy is providing any synchronous calls

Answer 1

You cannot make synchronous networking requests in Silverlight from the UI thread. There's no going around that. Even if you try to trick the asynchronous methods into behaving synchronously, it will not work. That's because if that were possible, the UI thread would be blocked, and the application would appear to be frozen. This happens because the responses to networking requests in SL are always delivered to the UI thread; if you wait for it on the UI thread itself, then you create a deadlock.

You essentially have two options: the preferred one is to actually go the asynchronous route. It's hard at first, if you're only used to synchronous programming, but it's a very valuable skill to have. The other option is to make the call on a background thread. I've tried it and it works, and some people have blogged about it , so you can try it as well. But AFAIK it's not officially supported.

Answer 2

Rather than just passing the callback parameter as the callback you'll want to assign your own callback that executes that method in addition to doing something else. You effectively just need to trigger an event of some sort. I have demonstrated one way using tasks, but you could just as easily use an auto reset event or one of any number of other synchronization methods.

void Getproducts(string filter, string augument, EventHandler<GetCompletedEventArgs> callback)
{
    var tcs = new TaskCompletionSource<bool>();
    _serviceclient.GetAsyncGetproducts(filter, argument, args =>
    {
        callback(args);
        tcs.SetResult(true);
    });

    tcs.Task.Wait();
}