1 BOOL APIENTRY DllMain( HMODULE hModule,    DWORD  ul_reason_for_call,LPVOID lpReserved)
 2 {
 3     switch (ul_reason_for_call)
 4     {
 5     case DLL_PROCESS_ATTACH:
 6     case DLL_THREAD_ATTACH:
 7     case DLL_THREAD_DETACH:
 8     case DLL_PROCESS_DETACH:
 9         break;
10     }
11     return TRUE;
12 }
13 
14 struct DevInfo//定义一个我自己的数据结构体
15 {
16     INT32 id;
17     char name[20];
18     char mac[25];
19     BYTE  data[100];
20 };
21 
22 extern "C" __declspec(dllexport) int sendTest(INT32 msg)//测试用的发布函数，这个int32参数一点作用都没有
23 {
24     DevInfo *pinfo=new DevInfo();
25     pinfo->id=999;
26     sprintf(pinfo->name,"myDevice");
27     sprintf(pinfo->mac,"19:4x:3a:4a");
28 
29     for (int i = 0; i < 100; i++)
30     {
31         pinfo->data[i]=(BYTE)(0x40+i);
32     }
33 
34     COPYDATASTRUCT cpd; /*给COPYDATASTRUCT结构赋值,COPYDATASTRUCT,这个也是系统自己定义的*/
35     cpd.dwData = 959;               //定义一个标示符（我这里没有用到）
36     cpd.cbData = sizeof(DevInfo);
37     cpd.lpData = pinfo;             //将指针的地址通过消息发送
38 
39     HWND handle2=::FindWindowA(NULL,(LPCSTR)"Form1");//获取窗口的句柄
40 
41     ::SendMessageA(handle2,WM_COPYDATA,(WPARAM)13,(LPARAM)&cpd);
42     
43     //这个地方必须要用sendMessageA，如果用post的话，则可能会出现数据还没有发送完
44     //系统就把定义的DevInfo 给清理掉了
45     
46     std::cout<<"发送数据消息"<<WM_COPYDATA<<std::endl;
47     delete pinfo;
48 
49     return 12;
50 }

 1 namespace Test
 2 {
 3     public partial class Form1 : Form
 4     {
 5         public Form1()
 6         {
 7             InitializeComponent();
 8         }
 9         
10         private const int WM_COPYDATA = 0x004A;//自己定义一个消息是必须的了
11         
12         [DllImport("BlueTooth4.dll", EntryPoint = "sendTest", CallingConvention = CallingConvention.Cdecl)]
13         public static extern Int32 sendTest(int msg);//我们刚才执行的事件，这个是为了测试用才这样做的
14         
15         
16         [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
17         public struct COPYDATASTRUCT//定义数据传输的结构
18         {
19             public IntPtr dwData;
20             public int cbData;
21             public IntPtr lpData;
22         }
23 
24         //定义要传递的Struct
25        [StructLayout(LayoutKind.Sequential)]//如果发现处理的数据有乱码的话，则在此处加上 ，CharSet = CharSet.Ansi
26        struct dataInfo
27        {
28            public IntPtr id;
29           
30             [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)]
31            public string name;
32 
33            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 25)]
34            public string mac;
35            
36            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 100)]
37            public byte[] data;
38        }
39 
40         protected override void DefWndProc(ref Message m)//开始处理消息
41         {
42             switch (m.Msg)
43             {
44                 //接收CopyData消息，读取发送过来的数据
45                 case WM_COPYDATA:
46                  COPYDATASTRUCT copydata = new COPYDATASTRUCT();  
47                  COPYDATASTRUCT RecvData = (COPYDATASTRUCT)m.GetLParam(typeof(COPYDATASTRUCT));
48                  dataInfo h = (dataInfo)Marshal.PtrToStructure((IntPtr)RecvData.lpData, typeof(dataInfo));//这句和上面的一句就已经将数据进行转换了
49                    break;
50                 default:
51                     base.DefWndProc(ref m);
52                     break;
53             }
54 
55         }
56     }
57 }