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

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;
}

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;
}

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）并读取 EmailEntity 类的字段。请注意，EmailEntity 类包含像 EmailAddress[] 这样的成员，它本身就是一个对象数组。我计划实现接口 IEmailEntity，它包含访问 EmailEntity 字段的属性，并使用它来访问 C++ 中的字段。那是正确的方法吗？

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

请建议。

谢谢

score 5 · Accepted Answer

您可以像这样简化 .NET 代码（删除所有应该自动完成的 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：在非托管 C++ 程序中实现 C# DLL COM 文件

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();
}

c# - 将对象数组从 C# 返回到 COM 中的 C

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