Question

我有一个Windows服务，它在运行时在另一个AppDomain中加载程序集。然后它执行它们，最后卸载AppDomain。问题是来自插件的execute方法是异步任务，我得到SerializationException，因为Task不从MarshalByRefObject继承。

我将插件包装在继承自MarshalByRefObject的代理中，但我不知道如何摆脱SerializationException？

public interface IPlugin : IDisposable
{
    Guid GUID { get; }
    string Name { get; }
    string Description { get; }
    Task Execute(PluginPanel panel, string user);
}

代理：

[Serializable()]
public class PluginProxy : MarshalByRefObject, IPlugin
{
    private IPlugin m_Plugin;

    public bool Init(string file)
    {
        Assembly ass = Assembly.Load(AssemblyName.GetAssemblyName(file));
        if (ass == null || ass.GetTypes() == null || ass.GetTypes().Length == 0)
            return false;
        foreach (Type type in ass.GetTypes())
        {
            if (type.IsInterface || type.IsAbstract)
                continue;
            if (type.GetInterface(typeof(IPlugin).FullName) != null)
            {
                m_Plugin = (IPlugin)Activator.CreateInstance(type);
                return true;
            }
        }
        return false;
    }


    public Guid GUID { get { return m_Plugin.GUID; } }
    public string Name { get { return m_Plugin.Name; } }
    public string Description { get { return m_Plugin.Description; } }
    // I debugged and found out the error happens AFTER m_Plugin.Execute
    // so the method runs well, but the return back to the pProxy.Execute is throwing the SerializationException       
    public async Task Execute(PluginPanel panel, string user) { await m_Plugin.Execute(panel, user); }
}

加载程序集并获取SerializationException的方法：

        AppDomainSetup setup = new AppDomainSetup();
        // some setup stuff

        AppDomain dom = AppDomain.CreateDomain(Guid.NewGuid().ToString(), null, setup);
        PluginProxy pProxy = (PluginProxy)dom.CreateInstanceFromAndUnwrap(Assembly.GetExecutingAssembly().CodeBase, typeof(PluginProxy).FullName);
        pProxy.Init(app.Apppath);
        // I await the task later in code, because the user can cancel the execution
        try { tExe = pProxy.Execute(panel, user.Username); }
           catch (System.Runtime.Serialization.SerializationException e)
           {
               // runs always in this catch, even if no Exception from the plugin was thrown
           }
           catch (Exception e) { AddToErrorLog(panel.PanelName, e); }
           finally
           {
               pProxy.Dispose();
               AppDomain.Unload(dom);
           }

也许我加载插件的整个概念都错了？

Answer 1

感谢Hamlet Hakobyan和Stephen Toub的帖子，我想我能够解决这个问题。

我从来电者

替换了这一行

 try { tExe = pProxy.Execute(panel, user.Username); }

带

 tExe = DoWorkInOtherDomain(pProxy, panel, user.Username);

和方法DoWorkInOtherDomain：

private Task DoWorkInOtherDomain(PluginProxy pProxy, PluginPanel panel, string user)
    {
        var ch = new MarshaledResultSetter<string>();
        pProxy.Execute(panel, user, ch);
        return ch.Task;
    }

最后是代理类：

 Task.Run(() =>
        {
            try
            {
                m_Plugin.Execute(panel, user).Wait();
            }
            catch (AggregateException e)
            {
                if (e.InnerExceptions != null)
                    foreach (Exception ein in e.InnerExceptions)
                        AddToErrorLog(panel.PanelName, ein);
            }
            catch (Exception e) { AddToErrorLog(panel.PanelName, e); }
            finally { ch.SetResult(AppDomain.CurrentDomain.FriendlyName); }
        });

我需要在

中调用Wait（）

m_Plugin.Execute(panel, user).Wait();

它从插件中捕获异常，所以一切都很好。 Wait（）调用应该只阻止Task.Run而不是其他任务。

有人可以告诉我这是一个很好的解决方案，还是应该改变一些东西？我不需要结果，所以我只是这样做：

 ch.SetResult(AppDomain.CurrentDomain.FriendlyName);

因为我不知道如何在没有结果的情况下这样做。

AppDomain等待异步任务阻止SerializationException

1 个答案: