c# - 将对象数组从 C# 返回到 COM 中的 C

Question

我正在使用 COM 在 C++ 和 C# 之间进行通信。

我在 C# 中有以下类

1. 电子邮件地址

   /// <summary>
   /// Email Address
   /// </summary>
   public class EmailAddress
   {
       /// <summary>
       /// SMTP Address
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]        
       public string Address;
   
       /// <summary>
       /// Name
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string Name;
   }
   

2. 邮箱

   /// <summary>
   /// MailBox Entity
   /// </summary>   
   public struct MailBoxEntity
   {
       /// <summary>
       /// SMTP Address
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string SMTPAddress;
   
       /// <summary>
       /// Mailbox Display Name
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string Name;
   
       /// <summary>
       /// Mailbox Server Name
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string sServerName;
   }
   

3. EmailEntity(尚未实现 IEmailEntity，它将包含每个字段的属性)

   /// <summary>
   /// Class for Email Entity
   /// </summary>
   public class EmailEntity : IEmailEntity
   {
       /// <summary>
       /// BccRecipients
       /// </summary>
       [MarshalAs(UnmanagedType.ByValArray)]
       public EmailAddress[] BccRecipients;
   
       /// <summary>
       /// Body
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string Body;
   
       /// <summary>
       /// CcRecipients
       /// </summary>
       [MarshalAs(UnmanagedType.ByValArray)]
       public EmailAddress[] CcRecipients;
   
       /// <summary>
       /// Culture
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string Culture;
   
       /// <summary>
       /// DateTimeCreated
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string DateTimeCreated;
   
       /// <summary>
       /// DateTimeReceived
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string DateTimeReceived;
   
       /// <summary>
       /// DateTimeSent
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string DateTimeSent;
   
       /// <summary>
       /// FromAddress
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string FromAddress;
   
       /// <summary>
       /// FromName
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string FromName;
   
   
       /// <summary>
       /// HasAttachments
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string HasAttachments;
   
       /// <summary>
       /// Id
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string Id;
   
       /// <summary>
       /// Importance
       /// </summary>
      [MarshalAs(UnmanagedType.BStr)]
       public string Importance;
   
       /// <summary>
       /// LastModifiedName
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string LastModifiedName;
   
       /// <summary>
       /// LastModifiedTime
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string LastModifiedTime;
   
       /// <summary>
       /// MimeContent
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string MimeContent;
   
       /// <summary>
       /// ParentFolderId
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string ParentFolderId;
   
       /// <summary>
       /// Original Mailbox
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public MailBoxEntity OriginalMailBox;
   
   
       /// <summary>
       /// ParentFolderName
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string ParentFolderName;
   
       /// <summary>
       /// ReceivedByAddress
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string ReceivedByAddress;
   
       /// <summary>
       /// ReceivedByName
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string ReceivedByName;
   
       /// <summary>
       /// Size
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string Size;
   
       /// <summary>
       /// Subject
       /// </summary>
       [MarshalAs(UnmanagedType.BStr)]
       public string Subject;
   
       /// <summary>
       /// ToRecipients
       /// </summary>
       [MarshalAs(UnmanagedType.ByValArray)]
       public EmailAddress[] ToRecipients;
   
   }
   

如何访问从 C# 中的函数返回的 EmailEnity 对象数组(在 C++ 中)并阅读 EmailEntity 类的字段。请注意，EmailEntity 类包含如下成员EmailAddress[] 本身就是一个对象数组。我正计划实现接口(interface) IEmailEntity，其中包含用于访问 EmailEntity 字段的属性并使用它来访问 C++ 中的字段。这是正确的方法吗？

如何在 C++ 中访问复杂的字段成员，例如 EmailAddress (EmailAddress[] ToRecipients) 数组。

请提出建议。

谢谢

Answer 1

您可以像这样简化 .NET 代码(删除所有应自动完成的 MarshalAs):

[ComVisible(true)]
public class MyRootClass : IMyRootClass // some class to start with
{
    public IEmailEntity[] GetEntities()
    {
        List<IEmailEntity> list = new List<IEmailEntity>();
        for(int i = 0; i < 10; i++)
        {
            EmailEntity entity = new EmailEntity();
            List<IEmailAddress> addresses = new List<IEmailAddress>();
            addresses.Add(new EmailAddress { Name = "Joe" + i });
            entity.BccRecipients = addresses.ToArray();
            entity.Body = "hello world " + i;
            list.Add(entity);
        }
        return list.ToArray();
    }   
}

[ComVisible(true)]
public interface IMyRootClass
{
    IEmailEntity[] GetEntities();
}

public class EmailEntity : IEmailEntity
{
    public IEmailAddress[] BccRecipients { get; set; }
    public string Body { get; set; }
}

public class EmailAddress : IEmailAddress
{
    public string Address { get; set; }
    public string Name { get; set; }
}

[ComVisible(true)]
public interface IEmailAddress
{
    string Address { get; set; }
    string Name { get; set; }
}

[ComVisible(true)]
public interface IEmailEntity
{
    IEmailAddress[] BccRecipients { get; set; }
    string Body { get; set; }
    // to be continued...
}

要将它与 C++ 一起使用，您需要注册 DLL 并构建一个 .TLB(类型库文件)，如此处类似答案中所述:Implement a C# DLL COM File In Unmanaged C++ Program

然后，您可以在 C++ 中访问这些类，如下所示:

#include "stdafx.h"
#import  "c:\MyPathToTheTlb\YourAssembly.tlb" // import the COM TLB

using namespace YourAssembly;

int _tmain(int argc, _TCHAR* argv[])
{
  CoInitialize(NULL);
  IMyRootClassPtr ptr(__uuidof(MyRootClass));
  CComSafeArray<IUnknown*> entities = ptr->GetEntities(); // CComSafeArray needs atlsafe.h in the PCH
  for(int i = entities.GetLowerBound(0); i <= entities.GetUpperBound(0); i++)
  {
    IEmailEntityPtr entity;
    entities.GetAt(i).QueryInterface(&entity);
    _bstr_t body = entity->Body;
    printf("%S\n", body.GetBSTR());

    CComSafeArray<IUnknown*> recipients = entity->BccRecipients;
    for(int j = recipients.GetLowerBound(0); j <= recipients.GetUpperBound(0); j++)
    {
      IEmailAddressPtr address;
      recipients.GetAt(j).QueryInterface(&address);
      _bstr_t name = address->Name;
      printf(" %S\n", name.GetBSTR());
    }
  }
  CoUninitialize();
}