.NET对象默认是自由线程的。如果通过COM编组到另一个线程,它们总是编组到它们自己,而不管创建线程是否为STA以及它们的ThreadingModel
注册表值如何。我怀疑它们聚合了Free Threaded Marshaler(有关COM线程的更多详细信息,请参见此处)。
我想让我的.NET COM对象在编组到另一个线程时使用标准的COM编组器代理。问题在于:
using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Threading;
namespace ConsoleApplication
{
class Program
{
static void Main(string[] args)
{
var apt1 = new WpfApartment();
var apt2 = new WpfApartment();
apt1.Invoke(() =>
{
var comObj = new ComObject();
comObj.Test();
IntPtr pStm;
NativeMethods.CoMarshalInterThreadInterfaceInStream(NativeMethods.IID_IUnknown, comObj, out pStm);
apt2.Invoke(() =>
{
object unk;
NativeMethods.CoGetInterfaceAndReleaseStream(pStm, NativeMethods.IID_IUnknown, out unk);
Console.WriteLine(new { equal = Object.ReferenceEquals(comObj, unk) });
var marshaledComObj = (IComObject)unk;
marshaledComObj.Test();
});
});
Console.ReadLine();
}
}
// ComObject
[ComVisible(true)]
[Guid("00020400-0000-0000-C000-000000000046")] // IID_IDispatch
[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
public interface IComObject
{
void Test();
}
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(IComObject))]
public class ComObject : IComObject
{
// IComObject methods
public void Test()
{
Console.WriteLine(new { Environment.CurrentManagedThreadId });
}
}
// WpfApartment - a WPF Dispatcher Thread
internal class WpfApartment : IDisposable
{
Thread _thread; // the STA thread
public System.Threading.Tasks.TaskScheduler TaskScheduler { get; private set; }
public WpfApartment()
{
var tcs = new TaskCompletionSource<System.Threading.Tasks.TaskScheduler>();
// start the STA thread with WPF Dispatcher
_thread = new Thread(_ =>
{
NativeMethods.OleInitialize(IntPtr.Zero);
try
{
// post a callback to get the TaskScheduler
Dispatcher.CurrentDispatcher.InvokeAsync(
() => tcs.SetResult(System.Threading.Tasks.TaskScheduler.FromCurrentSynchronizationContext()),
DispatcherPriority.ApplicationIdle);
// run the WPF Dispatcher message loop
Dispatcher.Run();
}
finally
{
NativeMethods.OleUninitialize();
}
});
_thread.SetApartmentState(ApartmentState.STA);
_thread.IsBackground = true;
_thread.Start();
this.TaskScheduler = tcs.Task.Result;
}
// shutdown the STA thread
public void Dispose()
{
if (_thread != null && _thread.IsAlive)
{
InvokeAsync(() => System.Windows.Threading.Dispatcher.ExitAllFrames());
_thread.Join();
_thread = null;
}
}
// Task.Factory.StartNew wrappers
public Task InvokeAsync(Action action)
{
return Task.Factory.StartNew(action,
CancellationToken.None, TaskCreationOptions.None, this.TaskScheduler);
}
public void Invoke(Action action)
{
InvokeAsync(action).Wait();
}
}
public static class NativeMethods
{
public static readonly Guid IID_IUnknown = new Guid("00000000-0000-0000-C000-000000000046");
public static readonly Guid IID_IDispatch = new Guid("00020400-0000-0000-C000-000000000046");
[DllImport("ole32.dll", PreserveSig = false)]
public static extern void CoMarshalInterThreadInterfaceInStream(
[In, MarshalAs(UnmanagedType.LPStruct)] Guid riid,
[MarshalAs(UnmanagedType.IUnknown)] object pUnk,
out IntPtr ppStm);
[DllImport("ole32.dll", PreserveSig = false)]
public static extern void CoGetInterfaceAndReleaseStream(
IntPtr pStm,
[In, MarshalAs(UnmanagedType.LPStruct)] Guid riid,
[MarshalAs(UnmanagedType.IUnknown)] out object ppv);
[DllImport("ole32.dll", PreserveSig = false)]
public static extern void OleInitialize(IntPtr pvReserved);
[DllImport("ole32.dll", PreserveSig = true)]
public static extern void OleUninitialize();
}
}
输出:
{ CurrentManagedThreadId = 11 } { equal = True } { CurrentManagedThreadId = 12 }
注意,我使用 CoMarshalInterThreadInterfaceInStream
/CoGetInterfaceAndReleaseStream
将一个 ComObject
从一个 STA 线程封送到另一个线程。作为一个解决方案,我想要两个 Test()
调用在同一原始线程上调用,例如 11
,就像在 C++ 实现的典型 STA COM 对象中那样。
一种可能的解决方案是禁用 .NET COM 对象上的 IMarshal
接口:
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(IComObject))]
public class ComObject : IComObject, ICustomQueryInterface
{
// IComObject methods
public void Test()
{
Console.WriteLine(new { Environment.CurrentManagedThreadId });
}
public static readonly Guid IID_IMarshal = new Guid("00000003-0000-0000-C000-000000000046");
public CustomQueryInterfaceResult GetInterface(ref Guid iid, out IntPtr ppv)
{
ppv = IntPtr.Zero;
if (iid == IID_IMarshal)
{
return CustomQueryInterfaceResult.Failed;
}
return CustomQueryInterfaceResult.NotHandled;
}
}
输出(期望的):
{ CurrentManagedThreadId = 11 } { equal = False } { CurrentManagedThreadId = 11 }
这个方法可以实现,但感觉像是一种特定于实现的hack。是否有更好的方法来完成这个操作,比如我可能忽略了某些特殊的interop属性?请注意,在现实生活中,ComObject
由一个遗留的非托管应用程序使用,并且被marshal。
await WpfApartment.InvokeAsync(()=>DoSomething())
这样的技术来在STA线程之间进行调用。 - noseratio - open to workComRegisterFunctionAttribute
将对象注册为ThreadingModel=Apartment
。然而,正如我上面提到的,这并不会改变我所描述的封送行为。非托管客户端在一个STA线程上调用CoMarshalInterThreadInterfaceInStream
,然后在另一个STA线程上调用CoGetInterfaceAndReleaseStream
,并获得相同的对象,而不是代理。这是因为任何.NET CCW都实现了IMarshal
并且是自由线程的,无论其在注册表中的ThreadingModel
如何。不要相信我的话,亲自试一试。 - noseratio - open to workIComObject
的GUID定义为IDispatch
的GUID? - acelentIDispatch
风格的封送。COM使用IDispatch::Invoke
,而.NET具有足够的元数据使这些IDispatch::Invoke
调用成为硬编码。 - noseratio - open to work