__declspec（dllexort）:: vector< std :: string> [英] __declspec(dllexport) ::vector<std::string>

问题描述

我一直在努力工作，如何从一个c ++ dll返回一个字符串数组到ac＃应用程序，但坚持如何做到这一点或找到一个非常基本的文章。

I've been trying to work out how to return an array of strings from a c++ dll to a c# application but am stuck on how to do this or find an article at a very basic level.

假设我有下面的代码。如何修改粗体线：

Suppose I have the code below. How do I fix the bolded line:

extern "C" {
    __declspec(dllexport) int GetANumber();

//unsure on this line:
    **__declspec(dllexport) ::vector<std::string> ListDevices();**

}

extern::vector<std::string> GetStrings()
{
    vector<string> seqs;
    return seqs;
}

extern int GetANumber()
{
    return 27;
}

感谢

Matt

推荐答案

您可以使用COM Automation SAFEARRAY 类型，即使没有做完整的COM（没有对象，没有类，没有接口，没有TLB，没有注册表等），只是与DLL导出，作为.NET本身用P / Invoke支持，类似这样：

You could use the COM Automation SAFEARRAY type, even without doing full COM (no object, no class, no interface, no TLB, no registry, etc.), just with DLL exports, as .NET supports it natively with P/Invoke, something like this:

C ++：

extern "C" __declspec(dllexport) LPSAFEARRAY ListDevices();

LPSAFEARRAY ListDevices()
{
    std::vector<std::string> v;
    v.push_back("hello world 1");
    v.push_back("hello world 2");
    v.push_back("hello world 3");

    CComSafeArray<BSTR> a(v.size()); // cool ATL helper that requires atlsafe.h

    std::vector<std::string>::const_iterator it;
    int i = 0;
    for (it = v.begin(); it != v.end(); ++it, ++i)
    {
        // note: you could also use std::wstring instead and avoid A2W conversion
        a.SetAt(i, A2BSTR_EX((*it).c_str()), FALSE);
    }
    return a.Detach();
}

C＃：

static void Main(string[] args)
{ 
    foreach(string s in ListDevices())
    {
        Console.WriteLine(s);
    }
}


[DllImport("MyUnmanaged.dll")]
[return: MarshalAs(UnmanagedType.SafeArray)] 
private extern static string[] ListDevices();

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