[C++知识库]如何用c#调用c++的dll传递各种稀奇古怪的参数。

声明

我知道用c#调用c++是个神烦的事情，在此分享部分传参心得和技巧，不一定是最好的方法，欢迎指正补充。

各种稀奇古怪的参数

1. 传递基础数据 int float double等

// h
extern "C" __declspec(dllexport) int TransData(int a, float b, double c);

// cpp
int TransData(int a, float b, double c) 
{
	double sum = a + b + c;
	return floor(sum);
}

//cs
[DllImport("贫道不是秃驴只是秃.dll", EntryPoint = "TransData", CallingConvention = CallingConvention.Cdecl)]
public static extern int TransData(int a, float b, double c);

2. 传递 string 并接收 string

// h
extern "C" __declspec(dllexport) const char* TransString(const char * inpStr);

// cpp
const char* TransString(const char* inpStr) 
{
	// 从const char * 到 std::string
	// std::string str = inpStr;
	// 从std::string 到  const char *
	// const char* pStr = str.c_str();
	std::string recive = inpStr;
	std::string demoStr = "我已经收到了：" + recive;
	return demoStr.c_str();
}

// cs
[DllImport("贫道不是秃驴只是秃.dll", EntryPoint = "TransString", CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr TransString(String msg);

// option
IntPtr str_ptr = DllLinker.TransString("我是你papa！");
string result = Marshal.PtrToStringAnsi(str_ptr);
Console.WriteLine(result);

3. 传递数组操作

// h
extern "C" __declspec(dllexport) int TransArr(int * arr, int arrLen);

// cpp
int TransArr(int* arr, int arrLen)
{
	int sum = 0;
	for (int i = 0; i < arrLen; i++) {
		sum += arr[i];
	}
	return sum;
}

// cs
[DllImport("贫道不是秃驴只是秃.dll", EntryPoint = "TransArr", CallingConvention = CallingConvention.Cdecl)]
public static extern int TransArr(int[] arr, int len);

// option
int[] arr = { 1,2,3,4,5};
int arrSum = DllLinker.TransArr(arr, arr.Length);
Console.WriteLine("数组值的和是：" + arrSum);

3. 传递结构体操作（包含数组，string等）（两种方式）

// h
extern "C" __declspec(dllexport) bool TransStructType1(YourSelf & yourSelf);
extern "C" __declspec(dllexport) void TransStructType2(YourSelf * yourSelf);

// cpp
bool TransStructType1(YourSelf& yourSelf) 
{
	yourSelf.age += 5;
	yourSelf.childrenId[0] = 1000;
	yourSelf.health = HealthType::DEATH;
	return true;
}
void TransStructType2(YourSelf* yourSelf)
{
	yourSelf->age += 5;
	yourSelf->childrenId[0] = 1000;
	yourSelf->health = HealthType::DEATH;
}

// cs
[DllImport("DLLS/Dll_DataFile.dll", EntryPoint = "TransStructType1", CallingConvention = CallingConvention.Cdecl)]
public static extern bool TransStructType1(ref YourSelf yourSelf);
[DllImport("DLLS/Dll_DataFile.dll", EntryPoint = "TransStructType2", CallingConvention = CallingConvention.Cdecl)]
public static extern void TransStructType2([In, Out] IntPtr yourSelf);

// option
int[] cid= { 1,2,3,4,5,6,7,8,9,0};
YourSelf yourSelf = new YourSelf();
yourSelf.age = 18;
yourSelf.money = 10.8f;
yourSelf.name = "ZhuDaChang";
yourSelf.childrenId = cid;
yourSelf.health = HealthType.OK;
// ============== 传参方式一 =============
bool res = DllLinker.TransStructType1(ref yourSelf);
Console.WriteLine("反馈bool:" + res + " ref影响yourself的属性age：" + yourSelf.age);
// ============== 传参方式二 =============
IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(YourSelf)));
Marshal.StructureToPtr(yourSelf, ptr, false);
DllLinker.TransStructType2(ptr);
YourSelf effectStruct = (YourSelf)Marshal.PtrToStructure(ptr, typeof(YourSelf));
Console.WriteLine("[in, out]影响yourself的属性age：" + effectStruct.age);
Marshal.FreeHGlobal(ptr);

4. 传递图片操作

这个可以参考我之前的一些博文，连接在下面：
c#调用c/c++打包的dll程序实现人脸检测（暨c#和c++之间传递图片解决方案）
c#的opencvsharp与c++封装opencv之间的mat对象传递（BitmapData造成图片扭曲的问题记录）