向 COM 公开 .NET 事件？

Question

我一直在尝试向 VBA 客户端公开和触发事件。到目前为止，在 VBA 客户端，事件已公开，我看到方法事件处理方法已添加到我的模块 class，但是 VBA 事件处理方法未触发。由于某种原因，调试时事件为空。同步修改我的代码也无济于事。

郑重声明，我检查了其他 SO 问题，但没有帮助。

任何好的答案将不胜感激。

[ComVisible(true)]
[Guid("56C41646-10CB-4188-979D-23F70E0FFDF5")]
[ClassInterface(ClassInterfaceType.None)]
[ComSourceInterfaces(typeof(IWebEvents))]
[ProgId("MyAssembly.MyClass")]
public class MyClass : ServicedComponent, IMyClass
{
    public string _address { get; private set; }
    public string _filename { get; private set; }

    [DispId(4)]
    public void DownloadFileAsync(string address, string filename)
    {
        _address = address;
        _filename = filename;
        System.Net.WebClient wc = new System.Net.WebClient();
        Task.Factory.StartNew(() => wc.DownloadFile(_address, _filename))
            .ContinueWith((t) =>
        {
            if (null != this.OnDownloadCompleted)
                OnDownloadCompleted();
        });
    }
    public event OnDownloadCompletedEventHandler OnDownloadCompleted;
}

[ComVisible(false)]
public delegate void OnDownloadCompletedEventHandler();

[ComVisible(true)]
[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
public interface IWebEvents
{
    [DispId(1)]
    void OnDownloadCompleted();
}

这是赏金猎人的好机会，200声望点数

Answer 1

.NET 代码中的关键概念是将事件定义为单独接口上的方法，并通过 [ComSourceInterfacesAttribute] 将其连接到 class。在示例中，这是使用以下代码完成的 [ComSourceInterfaces(typeof(IEvents))]，其中 IEvents 接口定义了应该在 COM 客户端上处理的事件。

事件命名注意事项：
c# class 中定义的事件名称和接口上定义的接口方法名称必须相同。在这个例子中 IEvents::OnDownloadCompleted 对应于 DemoEvents::OnDownloadCompleted.

然后定义了第二个接口，表示class本身的public API，这里称为IDemoEvents。在此接口上定义了在 COM 客户端上调用的方法。

C# code (builds to COMVisibleEvents.dll)

using System;
using System.EnterpriseServices;
using System.IO;
using System.Net;
using System.Runtime.InteropServices;
using System.Threading.Tasks;

namespace COMVisibleEvents
{
    [ComVisible(true)]
    [Guid("8403C952-E751-4DE1-BD91-F35DEE19206E")]
    [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
    public interface IEvents
    {
        [DispId(1)]
        void OnDownloadCompleted();
    }

    [ComVisible(true)]
    [Guid("2BF7DA6B-DDB3-42A5-BD65-92EE93ABB473")]
    [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
    public interface IDemoEvents
    {
        [DispId(1)]
        Task DownloadFileAsync(string address, string filename);
    }

    [ComVisible(true)]
    [Guid("56C41646-10CB-4188-979D-23F70E0FFDF5")]
    [ClassInterface(ClassInterfaceType.None)]
    [ComSourceInterfaces(typeof(IEvents))]
    [ProgId("COMVisibleEvents.DemoEvents")]
    public class DemoEvents
        : ServicedComponent, IDemoEvents
    {
        public delegate void OnDownloadCompletedDelegate();
        private event OnDownloadCompletedDelegate OnDownloadCompleted;
        public string _address { get; private set; }
        public string _filename { get; private set; }
        private readonly string _downloadToDirectory = 
            Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

        public async Task DownloadFileAsync(string address, string filename)
        {
            try
            {
                using (WebClient webClient = new WebClient())
                {
                    webClient.Credentials = new NetworkCredential(
                        "user", "psw", "domain");
                    string file = Path.Combine(_downloadToDirectory, filename);
                    await webClient.DownloadFileTaskAsync(new Uri(address), file)
                        .ContinueWith(t =>
                        {
                            // 
                            var ev = OnDownloadCompleted;
                            if (ev != null)
                            {
                                ev();
                            }
                        }, TaskScheduler.FromCurrentSynchronizationContext());
                }
            }
            catch (Exception ex)
            {
                // Log exception here ...
            }
        }
    }
}

regasm

C:\Windows\Microsoft.NET\Framework\v4.0.30319>regasm C:\Temp\COMVisibleEvents\bin\Debug\COMVisibleEvents.dll /tlb: C:\Temp\COMVisibleEvents\bin\Debug\COMVisibleEvents.tlb

VBA client reference to *.tlb file

添加对由 regasm 生成的 *tlb 的引用。这里 tlb 文件的名称是 COMVisibleEvents.

此处 Excel 用户表单用作 VBA 客户端。单击按钮后，将执行方法 DownloadFileAsync，当此方法完成时，事件将在处理程序 m_eventSource_OnDownloadCompleted 中捕获。在本示例中，您可以从我的保管箱下载 C# 项目的源代码 COMVisibleEvents.dll。

VBA client code (MS Excel 2007)

Option Explicit

Private WithEvents m_eventSource As DemoEvents

Private Sub DownloadFileAsyncButton_Click()
    m_eventSource.DownloadFileAsync "https://www.dropbox.com/s/0q3dskxopelymac/COMVisibleEvents.zip?dl=0", "COMVisibleEvents.zip"
End Sub

Private Sub m_eventSource_OnDownloadCompleted()
    MsgBox "Download completed..."
End Sub

Private Sub UserForm_Initialize()
    Set m_eventSource = New COMVisibleEvents.DemoEvents
End Sub

Result

向 COM 公开 .NET 事件？

Exposing .NET events to COM?

c#

com

events

vba