C# 中的 std::string ？
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std::string in C#?
提问by Ivan Prodanov
I thought the problem is inside my C++ function,but I tried this
我以为问题出在我的 C++ 函数中，但我试过了
C++ Function in C++ dll:
C++ dll 中的 C++ 函数：
bool __declspec( dllexport ) OpenA(std::string file)
{
return true;
}
C# code:
C#代码：
[DllImport("pk2.dll")]
public static extern bool OpenA(string path);
if (OpenA(@"E:\asdasd\"))
I get an exception that the memory is corrupt,why?
我得到一个内存损坏的异常，为什么？
If I remove the std::string parameter,it works great,but with std::string it doesnt work.
如果我删除 std::string 参数，它工作得很好，但使用 std::string 它不起作用。
采纳答案by shoosh
std::string and c# string are not compatible with each other. As far as I know the c# string corresponds to passing char*or wchar_t*in c++ as far as interop is concerned.
One of the reasons for this is that There can be many different implementations to std::string and c# can't assume that you're using any particular one.
std::string 和 c# 字符串彼此不兼容。据我所知，就互操作而言，c# 字符串对应于传递char*或wchar_t*在 c++ 中。
原因之一是 std::string 可以有许多不同的实现，而 c# 不能假设您正在使用任何特定的实现。
回答by Will Dean
Try something like this:
尝试这样的事情：
bool __declspec( dllexport ) OpenA(const TCHAR* pFile)
{
std::string filename(pFile);
...
return true;
}
You should also specify the appropriate character set (unicode/ansi) in your DllImport attribute.
您还应该在 DllImport 属性中指定适当的字符集（unicode/ansi）。
As an aside, unrelated to your marshalling problem, one would normally pass a std:string as a const reference: const std:string& filename.
顺便说一句，与您的编组问题无关，通常会将 std:string 作为常量引用传递：const std:string& 文件名。
回答by JaredPar
It's not possible to marshal a C++ std::string in the way you are attempting. What you really need to do here is write a wrapper function which uses a plain old const char*and converts to a std::string under the hood.
不可能以您尝试的方式编组 C++ std::string。你真正需要在这里做的是编写一个包装函数，它使用一个普通的旧函数const char*并在引擎盖下转换为 std::string 。
C++
C++
extern C {
void OpenWrapper(const WCHAR* pName) {
std::string name = pName;
OpenA(name);
}
}
C#
C＃
[DllImport("pk2.dll")]
public static extern void OpenWrapper( [In] string name);
回答by Nitay
I know this topic is a tad old but for future googlers, this should also work (without using char* in C++)
我知道这个话题有点旧，但对于未来的谷歌人来说，这也应该有效（在 C++ 中不使用 char*）
C#:
C＃：
public static extern bool OpenA([In, MarshalAs(UnmanagedType.LPStr)] path);
C++:
C++：
bool __declspec( dllexport ) OpenA(std::string file);
回答by sailfish009
std::wstring and System.string can be compatible through below conversion:
std::wstring 和 System.string 可以通过以下转换兼容：
C++ :
C++：
bool func(std::wstring str, int number)
{
BSTR tmp_str = SysAllocStringLen(str.c_str(), str.size());
VARIANT_BOOL ret = VARIANT_FALSE;
// call c# COM DLL
ptr->my_com_function(tmp_str, number, &ret);
SysFreeString(tmp_str);
return (ret != VARIANT_FALSE) ? true : false;
}
