Understanding Platform Invocation Services(Chapter 1 of COM and .NET Interoperability) part3

 1 #include "MyCustomCallbackDLL.h"
 2 
 3 BOOL APIENTRY DllMain( HANDLE hModule, 
 4                        DWORD  ul_reason_for_call, 
 5                        LPVOID lpReserved)
 6 {
 7     return TRUE;
 8 }
 9 
10 // THEPOINT Callback prototype.
11 typedef bool (CALLBACK *POINTCALLBACKFUNCTION)( THEPOINT* i );
12 
13 // Simple Callback prototype.
14 typedef bool (CALLBACK *SIMPLECALLBACKFUNCTION)();
15 
16 extern "C" MYCUSTOMCALLBACKDLL_API void ChangePOINTAndReportBack(POINTCALLBACKFUNCTION pf, THEPOINT* thePoint)
17 {
18    MessageBox(NULL, "Received THEPOINT and am about to change it...", 
19        "Unmanaged DLL", MB_OK);
20 
21     // Take the incoming THEPOINT and change it.
22     thePoint->x = 10000;
23     thePoint->y = 20000;
24    
25     // Call the managed function.
26     bool res = (*pf)(thePoint);
27 
28     // Get result from callback.
29     if( res )
30         MessageBox(NULL, "Callback says TRUE", 
31             "Unmanaged DLL", MB_OK);
32     else
33         MessageBox(NULL, "Callback says FALSE", 
34             "Unmanaged DLL", MB_OK);
35 }
36 
37 extern "C" MYCUSTOMCALLBACKDLL_API void VerifyAndReportBack(SIMPLECALLBACKFUNCTION pf)
38 {
39    MessageBox(NULL, "You called me...about to call you!", 
40        "Unmanaged DLL", MB_OK);
41    
42     // Call the managed function.
43     bool res = (*pf)();
44 
45     // Get result from callback.
46     if( res )
47         MessageBox(NULL, "Callback says TRUE", 
48             "Unmanaged DLL", MB_OK);
49     else
50         MessageBox(NULL, "Callback says FALSE", 
51             "Unmanaged DLL", MB_OK);
52 }

 

 1 using System;
 2 using System.Runtime.InteropServices;
 3 
 4 namespace CustomCallbackClient
 5 {
 6     // A simple struct to pass to the DLL.
 7     [StructLayout(LayoutKind.Sequential)]
 8     public class THEPOINT
 9     {
10         public int x;
11         public int y;
12     }
13 
14     class ManagedCallBackApp
15     {
16         public delegate bool SendTHEPOINTHere(THEPOINT pt);
17         public delegate bool ReportBackHere();
18 
19         [DllImport("MyCustomCallbackDLL.dll")]
20         public static extern void VerifyAndReportBack(ReportBackHere x);
21 
22         [DllImport("MyCustomCallbackDLL.dll")]
23         public static extern void ChangePOINTAndReportBack(SendTHEPOINTHere x, THEPOINT pt);
24 
25         [STAThread]
26         public static void Main() 
27         {
28             ReportBackHere simpleCallback = new ReportBackHere(ManagedCallBackApp.Report);
29             VerifyAndReportBack(simpleCallback);
30 
31             SendTHEPOINTHere theCallBack = new SendTHEPOINTHere(ManagedCallBackApp.GiveMeThePoint);
32             THEPOINT pt = new THEPOINT();
33             pt.x = 10;
34             pt.y = 10;
35             Console.WriteLine("Point is:");
36             Console.WriteLine("X = {0}\nY = {1}", pt.x, pt.y);
37             ChangePOINTAndReportBack(theCallBack, pt);
38         }
39 
40         public static bool GiveMeThePoint(THEPOINT pt) 
41         { 
42             Console.WriteLine("New Point is:");
43             Console.WriteLine("X = {0}\nY = {1}", pt.x, pt.y);
44             return true;
45         }
46 
47         public static bool Report() 
48         { 
49             Console.WriteLine("I was called by the DLL!");
50             return false;
51         }
52 
53     }
54 }