C# 调用C++ 结构体示例

C++ 定义

typedef struct Stu
{
public:
int Age;
char Name[20];
};

typedef struct Num
{
int N1;
int N2;
};

extern "C" __declspec(dllexport) void FindInfo(Stu& stu)
{
stu.Age = 10;
strcpy_s(stu.Name, "徐滔");
}

extern "C" __declspec(dllexport) int Add(int a,int b)
{
return a + b;
}

extern "C" __declspec(dllexport) int GetNumSum(Num* num)
{
return num->N1 + num->N2;
}

extern "C" __declspec(dllexport) bool InputInfo(int age,char name[20], Stu* stuInfo)
{
stuInfo->Age = age;
char* test = name;
strcpy_s(stuInfo->Name, name);
return true;
}

在C# 中需要重新定义结构

[System.Runtime.InteropServices.StructLayout(LayoutKind.Sequential)]
public struct Stu
{
public int Age;
[System.Runtime.InteropServices.MarshalAs(UnmanagedType.ByValTStr,SizeConst =20)]
public string Name;
}

注意c# 中 和c++ 中的数据类型的对应。

public struct Num
{
public int N1;
public int N2;
}

申明 调用函数

[DllImport("MyFuncDll.dll", EntryPoint = "FindInfo", CallingConvention = CallingConvention.Cdecl,
CharSet = CharSet.Unicode)]
extern static void FindInfo(ref Stu stu);
[DllImport("MyFuncDll.dll", EntryPoint = "Add", CallingConvention = CallingConvention.Cdecl)]
public extern static int Add(int a, int b);

[DllImport("MyFuncDll.dll", EntryPoint = "GetNumSum", CallingConvention = CallingConvention.Cdecl)]
public extern static int GetNumSum(ref Num num);

[DllImport("MyFuncDll.dll", EntryPoint = "InputInfo", CallingConvention = CallingConvention.Cdecl,
CharSet =CharSet.Ansi)]

特别要注意 CharSet 属性的设置。

调用测试

int re = Add(1, 3);
Num n = new Num() { N1 = 1, N2 = 2 };
int r = GetNumSum(ref n);
Stu stu = new UseCppDll.Stu();
FindInfo(ref stu);
MessageBox.Show(stu.Name);

在c#中调用C++传递 char[]类型的参数

string sna = "系统";
bool b = InputInfo(23, sna, ref stuInfo);

//-------------------------------------------------------------

C# 调用 C++ dll返回字符串问题

做个简单的例子，将传入的字符串复制后再返回…

C++中定义方法：

EXTERN_C __declspec(dllexport) bool TryCopyStr(char* src, char** desstr)
{
    _memccpy(*desstr, src,0, strlen(src));
     return true;
}

参数： src —源字符串

参数：desstr—目标字符串（也就是要将返回值赋给该参数），注意其类型为 char**

C# 代码：

//dll调用申明

[DllImport("dotNetCppStrTest.dll", EntryPoint = "TryCopyStr", CallingConvention = CallingConvention.Cdecl)]
public extern static bool TryCopyStr(string src,ref StringBuilder desStr);

//测试方法

private void TestTryGetStr()

{

        bool suc = false;
        StringBuilder resultStrBuilder = new StringBuilder();
        string srcStr = "this is string from .net 从.net传过去的字符串";
        suc = TryCopyStr(srcStr,ref resultStrBuilder);

}

注：

     参数 desStr 是 StringBuilder 类型，而不是 String 类型。因为在dll中对该参数进行了重新赋值，也即是参数值发生了改变，String 类型的值是不能改变的。

     此方法在VS2015测试通过。