Question

我需要在我的应用中使用跨appdomain调用，有时我有这个RemotingException：

对象'/2fa53226_da41_42ba_b185_ec7d9c454712/ygiw+xfegmkhdinj7g2kpkhc_7.rem'已断开连接或在服务器上不存在。

目标对象仍然存在，我已经检查过了。

UPD我在目标对象的终结器中设置断点，它永远不会命中。因此，这个对象是活着的，而不是GC。

Answer 1

这可能是因为服务器端的本地垃圾收集器收集了该对象。您可以通过续订租赁来防止这种情况。您可以在这些文章中阅读更多相关内容：

更新：不幸的是，MSDN杂志2008年或更早版本的问题不再可以在线浏览，而只能作为必须下载到本地计算机的.chm文件。以前的问题可以在以下网站找到：

在December 2003 issue
CLR Inside Out：在November 2007 issue

Answer 2

这是因为服务器端的Lifetime管理在租约到期时断开对象，以允许GC收集它。如果您尝试从客户端使用它，您将得到一个例外，即使它尚未在服务器上进行GC（例如因为还有另一个引用）但租约已过期。这是为了避免不可预测的行为。接受的答案为如何正确管理远程.NET对象的生命周期提供了很好的参考。

Answer 3

我遇到了同样的问题，在许多StackOverflow帖子的帮助下我搜索了很多个小时。

我终于找到了完整的问题。

我必须使用赞助商来维持我的MarshalByRefObject。
然后我遇到了与@ user626528相同的问题：对象还活着，但我有异常。事实上，我需要“赞助”所有“TransparentProxy”实例，而不仅仅是主要的：我在SandBox中创建的主要对象（另一个AppDomain）返回对其他MarshalByRefObjects的引用。

以下是完整的解释和用例：

我的类“Loader”继承自MarshalByRefObject，我使用ISponsor类保持活着。我知道.NET中存在“ClientSponsor”，但我无法确定是否以及何时调用Renewal（），所以我在StackOverflow社区的帮助下创建了我的类（阅读代码注释）：

/// <see cref="https://stackoverflow.com/questions/18680664/remoting-sponsor-stops-being-called"/>
public class RemotingSponsor : MarshalByRefObject, ISponsor, IDisposable
{
    /*
     * @CoryNelson said :
     * I've since determined that the ILease objects of my sponsors 
     * themselves are being GCed. They start out with the default 5min lease 
     * time, which explains how often my sponsors are being called. When I 
     * set my InitialLeaseTime to 1min, the ILease objects are continually        
     * renewed due to their RenewOnCallTime being the default of 2min.
     * 
     */ 

    ILease _lease;

    public RemotingSponsor(MarshalByRefObject mbro)
    {
        _lease = (ILease)RemotingServices.GetLifetimeService(mbro);
        if (_lease == null) throw new NotSupportedException("Lease instance for MarshalByRefObject is NULL");
        _lease.Register(this);
    }

    public TimeSpan Renewal(ILease lease)
    {
        Debug.WriteLine("RemotingSponsor.Renewal called");
        return this._lease != null ? lease.InitialLeaseTime : TimeSpan.Zero;
    }


    public void Dispose()
    {
        if (_lease != null)
        {
            _lease.Unregister(this);
            _lease = null;
        }
    }

    public override object InitializeLifetimeService()
    {
        /*
         *
         * @MatthewLee said:
         *   It's been a long time since this question was asked, but I ran into this today and after a couple hours, I figured it out. 
         * The 5 minutes issue is because your Sponsor which has to inherit from MarshalByRefObject also has an associated lease. 
         * It's created in your Client domain and your Host domain has a proxy to the reference in your Client domain. 
         * This expires after the default 5 minutes unless you override the InitializeLifetimeService() method in your Sponsor class or this sponsor has its own sponsor keeping it from expiring.
         *   Funnily enough, I overcame this by returning Null in the sponsor's InitializeLifetimeService() override to give it an infinite timespan lease, and I created my ISponsor implementation to remove that in a Host MBRO.
         * Source: https://stackoverflow.com/questions/18680664/remoting-sponsor-stops-being-called
        */
        return (null);
    }
}

然后我就像这样使用这个“自定义赞助商”：

// Loader and Container for MarshalByRefObject in another domain
 public class PluginFile : IDisposable
 {
           private RemotingSponsor _sponsor; // Keep instance not to have Sponsor Garbage Collected
           private AppDomain _sandbox;
           private ICustomPlugin[] _plugins; // I do not store real instances of Plugins, but a "CustomPluginProxy" which is known both by main AppDomain and Plugin AppDomain.

    // Constructor : load an assembly file in another AppDomain (sandbox)
    public PluginFile(System.IO.FileInfo f, AppDomainSetup appDomainSetup, Evidence evidence)
    {
        Directory = System.IO.Path.GetDirectoryName(f.FullName) + @"\";
        _sandbox = AppDomain.CreateDomain("sandbox_" + Guid.NewGuid(), evidence, appDomainSetup);

        _sandbox.Load(typeof(Loader).Assembly.FullName);

        // - Instanciate class "Loader" INSIDE OTHER APPDOMAIN, so we couldn't use new() which would create in main AppDomain.
        _loader = (Loader)Activator.CreateInstance(
            _sandbox,
            typeof(Loader).Assembly.FullName,
            typeof(Loader).FullName,
            false,
            BindingFlags.Public | BindingFlags.Instance,
            null,
            null,
            null,
            null).Unwrap();

        // - Load plugins list for assembly
        _plugins= _loader.LoadPlugins(f.FullName); 


        // - Keep object created in other AppDomain not to be "Garbage Collected". I create a sponsor. The sponsor in registed for object "Lease". The LeaseManager will check lease expiration, and call sponsor. Sponsor can decide to renew lease. I not renewed, the object is garbage collected.
        // - Here is an explanation. Source: https://stackoverflow.com/questions/12306497/how-do-the-isponsor-and-ilease-interfaces-work
        _sponsor = new RemotingSponsor(_loader);

       // Here is my SOLUTION after many hours ! I had to sponsor each MarshalByRefObject (plugins) and not only the main one that contains others !!!
       foreach (ICustomPlugin plugin in Plugins) 
        {
            ILease lease = (ILease)RemotingServices.GetLifetimeService((PluginProxy)plugin);
            lease.Register(_sponsor); // Use the same sponsor. Each Object lease could have as many sponsors as needed, and each sponsor could be registered in many Leases.
        }
    }

 }

PluginProxy类型具有对真实插件类型的引用。实际上，PluginProxy在Plugin AppDomain中实现，并返回到主AppDomain，允许它调用插件，即使它忽略了它们的真实类型。因此，可以从主AppDomain访问的PluginProxy必须序列化以跨越AppDomains限制。我遇到了问题，因为我没有赞助这些MarshalByRefObject：

 /// <see cref="https://stackoverflow.com/questions/4185816/how-to-pass-an-unknown-type-between-two-net-appdomains"/>
    [Serializable]
    public class PluginProxy : MarshalByRefObject, ICustomPlugin
    {
        private ICustomPlugin _hostedPlugin;            

        /// <summary>
        /// Parameterless constructor for deserialization 
        /// </summary>
        public PluginProxy()
        {             
        }

        ~PluginProxy()
        {
            Debug.WriteLine("DESTRUCTOR ~PluginProxy");
        }

        /// <summary>
        /// Constructor reserved from real Plugin type
        /// </summary>
        /// <param name="name"></param>
        public PluginProxy(ICustomPlugin hostedPlugin)
        {
            _hostedPlugin = hostedPlugin;
        }

        public PluginName Name => _hostedPlugin.Name;

        public PluginResult Execute(PluginParameters parameters, PluginQuery query)
        {
            return(_hostedPlugin.Execute(parameters, query));
        }
    }

要解决这个问题很困难，希望这会有所帮助！

参考文献：

MSDN：ILease interface
MSDN：ObjRef class
Microsoft：How to marshal an object to a remote server by reference by using Visual C#
StackOverflow：Remoting sponsor stops being called
StackOverflow：How do the ISponsor and ILease interfaces work?
StackOverflow：How to pass an unknown type between two .NET AppDomains?
StackOverflow：AppDomain and MarshalByRefObject life time : how to avoid RemotingException?
StackOverflow：MarshalByRefObject becoming “disconnected at server” even while sponsored

Answer 4

这发生在我们身上，因为我们在其中一个类中有一个静态变量，类型为AppDomain。该类在长时间运行的Windows服务中使用。 AppDomain有一个InitializeLifetimeService方法，需要像这样重写：

public override object InitializeLifetimeService(){
    return null;
}

我们一直在使用它作为私有变量，它为自定义的外部逻辑加载和卸载了一些dll。答案是从这里获得的：msdn answer

由于我们无法在生产时更改此设置，因此以折衷的方式进行了折衷，即以比静态AppDomain变量的生存期短的随机间隔重新启动Windows服务，通过反复试验，我们发现它是几个天。

此问题还有助于弄清有关寿命的一些问题：stackoverflow-question

Answer 5

这个问题是answered in great detail already on StackOverflow。 TL / DR：

如果要让Singleton语义覆盖InitializeLifetimeService to return null
使用ClientSponsor使您的对象存活更长的时间。

Answer 6

在我的情况下，问题是在客户端计算机中，有一个虚拟网络适配器处于活动状态，禁用虚拟网络适配器，问题解决了

Answer 7

在我的情况下，这发生在存储在App_Data项目内的Web文件夹中的SQL LocalDB中。每当我尝试使用Package Console运行update-database来使用迁移来初始化我的Entity Framework数据库时，都不会发生任何事情。过了一会儿，我得到了那个错误。

我通过修改App_Data上的文件权限解决了这个问题。一旦修好，瞧，它有效。

“对象已断开连接或在服务器上不存在”异常

7 个答案: