如何在 C# 中调用 C++ DLL
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How to call C++ DLL in C#
提问by user1333098
I have written a DLL in dev C++. The DLL's name is "DllMain.dll" and it contains two functions: HelloWorldand ShowMe. The header file looks like this:
我已经用 dev C++ 编写了一个 DLL。DLL 的名称是“DllMain.dll”，它包含两个函数：HelloWorld和ShowMe. 头文件如下所示：
DLLIMPORT void HelloWorld();
DLLIMPORT void ShowMe();
And the source file looks like this:
源文件如下所示：
DLLIMPORT void HelloWorld ()
{
MessageBox (0, "Hello World from DLL!\n", "Hi",MB_ICONINFORMATION);
}
DLLIMPORT void ShowMe()
{
MessageBox (0, "How are u?", "Hi", MB_ICONINFORMATION);
}
I compile the code into a DLL and call the two functions from C#. The C# code looks like this:
我将代码编译成 DLL 并从 C# 调用这两个函数。C# 代码如下所示：
[DllImport("DllMain.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern void HelloWorld();
[DllImport("DllMain.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern void ShowMe();
When I call the function "HelloWorld" it runs well and pops up a messageBox, but when I call the function ShowMean EntryPointNotFoundExceptionoccurs. How do I avoid this exception? Do I need to add extern "C"in the header file?
当我打电话功能的“HelloWorld”，它运行良好，弹出一个消息框，但是当我调用该函数ShowMe的EntryPointNotFoundException发生。如何避免此异常？我需要extern "C"在头文件中添加吗？
采纳答案by atoMerz
The following code in VS 2012 worked fine:
VS 2012 中的以下代码运行良好：
#include <Windows.h>
extern "C"
{
__declspec(dllexport) void HelloWorld ()
{
MessageBox (0, L"Hello World from DLL!\n", L"Hi",MB_ICONINFORMATION);
}
__declspec(dllexport) void ShowMe()
{
MessageBox (0, L"How are u?", L"Hi", MB_ICONINFORMATION);
}
}
NOTE:If I remove the extern "C"I get exception.
注意：如果我删除extern "C"我得到异常。
回答by mjb
using System;
using System.Runtime.InteropServices;
namespace MyNameSpace
{
public class MyClass
{
[DllImport("DllMain.dll", EntryPoint = "HelloWorld")]
public static extern void HelloWorld();
[DllImport("DllMain.dll", EntryPoint = "ShowMe")]
public static extern void ShowMe();
}
}
回答by Shimon Doodkin
things that helped:
有帮助的事情：
The: extern "C" { function declarations here in h file } will disable C++ name encoding. so c# will find the function
Use __stdcall for the C declaration or CallingConvention.Cdecl in the C# declaration
maybe use BSTR/_bstr_t as string type and use other vb types. http://support.microsoft.com/kb/177218/EN-US
download "PInvoke Interop Assistant" https://clrinterop.codeplex.com/releases/view/14120paste function declaration from .h file in the 3rd tab = c# declaration. replace with dll filename.
: extern "C" { function declarations here in h file } 将禁用 C++ 名称编码。所以c#会找到这个函数
将 __stdcall 用于 C 声明或 C# 声明中的 CallingConvention.Cdecl
也许使用 BSTR/_bstr_t 作为字符串类型并使用其他 vb 类型。http://support.microsoft.com/kb/177218/EN-US
下载“PInvoke Interop Assistant” https://clrinterop.codeplex.com/releases/view/14120从.h 文件中的第三个选项卡= c# 声明中粘贴函数声明。替换为 dll 文件名。
