Develop Reference

C# to C++ CopyData API

I am developing an automation interface program and I looking to enhance capability with a machine software which uses a COPYDATA API aimed at C++. The goal is to control and report status of the machine through my own software.
The method uses pointers and memory allocation which I have not had any experience with thus far.
I have looked at a number of other sources, such as this with no luck at the moment. I have tried the following code to try and run a program on the machine software.
class Program
{
[DllImport("User32.dll", SetLastError = true, EntryPoint = "FindWindow")]
public static extern IntPtr FindWindow(String lpClassName, String lpWindowName);
[DllImport("User32.dll", SetLastError = true, EntryPoint = "SendMessage")]
public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, ref COPYDATASTRUCT lParam);
[StructLayout(LayoutKind.Sequential)]
public struct COPYDATASTRUCT
{
public IntPtr dwData; // Any value the sender chooses. Perhaps its main window handle?
public int cbData; // The count of bytes in the message.
public IntPtr lpData; // The address of the message.
}
const int WM_COPYDATA = 0x004A;
const int EXTERNAL_CD_COMMAND_RUN_ASYNC = 0x8001;
static void Main(string[] args)
{
Console.WriteLine("{0} bit process.", (IntPtr.Size == 4) ? "32" : "64");
Console.Write("Press ENTER to run test.");
Console.ReadLine();
IntPtr hwnd = FindWindow(null, "InSpecAppFrame");
Console.WriteLine("hwnd = {0:X}", hwnd.ToInt64());
var cds = new COPYDATASTRUCT();
byte[] buff = Encoding.ASCII.GetBytes("C:\\Users\\Desktop\\COPYDATATEST.iwp");
cds.dwData = (IntPtr)EXTERNAL_CD_COMMAND_RUN_ASYNC;
cds.lpData = Marshal.AllocHGlobal(buff.Length);
Marshal.Copy(buff, 0, cds.lpData, buff.Length);
cds.cbData = buff.Length;
var ret = SendMessage(hwnd, WM_COPYDATA, 0, ref cds);
Console.WriteLine("Return value is {0}", ret);
Marshal.FreeHGlobal(cds.lpData);
Console.ReadLine();
}
}
Running this code returns 0 for both hwnd and ret and the machine software does not react.
Sending a command is the first step, the next will be to try and get a response so I can monitor machine statuses etc.

As a sidenote to what Alejandro wrote (and that I think is correct), you can simplify a little the code, removing a copy of the data. You can directly "pin" your byte[]. It is important that you remember to "unpin" it (for this reason the try/finally block)
There is another potential problem in your code (a problem that I saw only on a second pass of the code): C strings must be \0 terminated (so "Foo" must be "Foo\0"). Your Encoding.ASCII doesn't guarantee a \0 termination. The classical way to do it is to make the byte[] "a little larger" than necessary. I've done the changes necessary.
[DllImport("User32.dll", SetLastError = true)]
public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, ref COPYDATASTRUCT lParam);
[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
[StructLayout(LayoutKind.Sequential)]
public struct COPYDATASTRUCT
{
public IntPtr dwData; // Any value the sender chooses. Perhaps its main window handle?
public int cbData; // The count of bytes in the message.
public IntPtr lpData; // The address of the message.
}
[StructLayout(LayoutKind.Sequential)]
public struct ExternalGetPositionType
{
public double X;
public double Y;
public double Z;
public double W;
}
const int WM_COPYDATA = 0x004A;
const int EXTERNAL_CD_COMMAND_RUN_ASYNC = 0x8001;
const int EXTERNAL_CD_GET_POSITION_PCS = 0x8011;
const int EXTERNAL_CD_GET_POSITION_MCS = 0x8012;
static void Main(string[] args)
{
Console.WriteLine("{0} bit process.", (IntPtr.Size == 4) ? "32" : "64");
Console.Write("Press ENTER to run test.");
Console.ReadLine();
IntPtr hwnd = FindWindow(null, "Form1");
Console.WriteLine("hwnd = {0:X}", hwnd.ToInt64());
if (hwnd == IntPtr.Zero)
{
throw new Exception("hwnd not found");
}
IntPtr ret = RunAsync(hwnd, #"C:\Users\Desktop\COPYDATATEST.iwp");
Console.WriteLine($"Return value for EXTERNAL_CD_COMMAND_RUN_ASYNC is {ret}");
ret = GetPosition(hwnd, true, new ExternalGetPositionType { X = 1, Y = 2, Z = 3, W = 4 });
Console.WriteLine($"Return value for EXTERNAL_CD_GET_POSITION_PCS is {ret}");
ret = GetPosition(hwnd, false, new ExternalGetPositionType { X = 10, Y = 20, Z = 30, W = 40 });
Console.WriteLine($"Return value for EXTERNAL_CD_GET_POSITION_MCS is {ret}");
Console.ReadLine();
}
public static IntPtr RunAsync(IntPtr hwnd, string str)
{
// We have to add a \0 terminator, so len + 1 / len + 2 for Unicode
int len = Encoding.Default.GetByteCount(str);
var buff = new byte[len + 1]; // len + 2 for Unicode
Encoding.Default.GetBytes(str, 0, str.Length, buff, 0);
IntPtr ret;
GCHandle h = default(GCHandle);
try
{
h = GCHandle.Alloc(buff, GCHandleType.Pinned);
var cds = new COPYDATASTRUCT();
cds.dwData = (IntPtr)EXTERNAL_CD_COMMAND_RUN_ASYNC;
cds.lpData = h.AddrOfPinnedObject();
cds.cbData = buff.Length;
ret = SendMessage(hwnd, WM_COPYDATA, 0, ref cds);
}
finally
{
if (h.IsAllocated)
{
h.Free();
}
}
return ret;
}
public static IntPtr GetPosition(IntPtr hwnd, bool pcs, ExternalGetPositionType position)
{
// We cheat here... It is much easier to pin an array than to copy around a struct
var positions = new[]
{
position
};
IntPtr ret;
GCHandle h = default(GCHandle);
try
{
h = GCHandle.Alloc(positions, GCHandleType.Pinned);
var cds = new COPYDATASTRUCT();
cds.dwData = pcs ? (IntPtr)EXTERNAL_CD_GET_POSITION_PCS : (IntPtr)EXTERNAL_CD_GET_POSITION_MCS;
cds.lpData = h.AddrOfPinnedObject();
cds.cbData = Marshal.SizeOf<ExternalGetPositionType>();
ret = SendMessage(hwnd, WM_COPYDATA, 0, ref cds);
}
finally
{
if (h.IsAllocated)
{
h.Free();
}
}
return ret;
}
Note even that instead of ASCII you can use the Default encoding, that is a little better.
If you want to receive the messages, in your Winforms do:
protected override void WndProc(ref Message m)
{
if (m.Msg == WM_COPYDATA)
{
COPYDATASTRUCT cds = Marshal.PtrToStructure<COPYDATASTRUCT>(m.LParam);
if (cds.dwData == (IntPtr)EXTERNAL_CD_COMMAND_RUN_ASYNC)
{
string str = Marshal.PtrToStringAnsi(cds.lpData);
Debug.WriteLine($"EXTERNAL_CD_COMMAND_RUN_ASYNC: {str}");
m.Result = (IntPtr)100; // If you want to return a value
}
else if (cds.dwData == (IntPtr)EXTERNAL_CD_GET_POSITION_PCS)
{
if (cds.cbData >= Marshal.SizeOf<ExternalGetPositionType>())
{
var position = Marshal.PtrToStructure<ExternalGetPositionType>(cds.lpData);
Debug.WriteLine($"EXTERNAL_CD_GET_POSITION_PCS: X = {position.X}, Y = {position.Y}, Z = {position.Z}, W = {position.W}");
m.Result = (IntPtr)200;
}
else
{
m.Result = (IntPtr)0;
}
}
else if (cds.dwData == (IntPtr)EXTERNAL_CD_GET_POSITION_MCS)
{
if (cds.cbData >= Marshal.SizeOf<ExternalGetPositionType>())
{
var position = Marshal.PtrToStructure<ExternalGetPositionType>(cds.lpData);
Debug.WriteLine($"EXTERNAL_CD_GET_POSITION_MCS: X = {position.X}, Y = {position.Y}, Z = {position.Z}, W = {position.W}");
m.Result = (IntPtr)300;
}
else
{
m.Result = (IntPtr)0;
}
}
return;
}
base.WndProc(ref m);
}
Note that if you control both the sender AND the receiver, it is better much better to use Unicode for the string parameter. You'll have to modify both the sender and the receiver: Encoding.Unicode.GetByteCount/Encoding.Unicode.GetBytes, the +2 instead of +1 and Marshal.PtrToStringUni.

Marshaling Struct Array with Strings Between c# and c++. Strings are empty

I am having the most difficult time marshaling this struct between C# and C++.
What makes it very hard to troubleshoot is that SOMETIMES the strings are populated with data (wtf), but most of the time they are not.
I've tried sending over an Array of structs as well as a IntPtr, but the results are similar, the strings in the struct are almost always empty and I can't figure out what I'm doing wrong in the marshaling. The code is posted below. Any help would be appreciated.
Edit***
Turns out the problem was on the C++ side and all the marshaling stuff was correct. Thanks for the tip Hans. ***
C++:
#pragma pack (push, 1)
typedef struct
{
char FirmwareVers[FS_MAX_FIRMWARE_VER];
char SerialNum[FS_MAX_SERIAL_NUM];
char HardwareVers[FS_MAX_HW_VER];
ULONG StatusFlags;
int LMIndex;
} FS_LMON_STATUS, *PFS_LMON_STATUS;
DllExport int _stdcall FS_GetLMs(PFS_LMON_STATUS pLaunchMonInfo, int MaxLaunchMons, int *pNumLaunchMons)
{
int Cnt;
FS_LMON_STATUS LMStatus;
if(!g_IsInitalized)
return FS_NOT_INITALIZED;
*pNumLaunchMons = 0;
if(MaxLaunchMons == 0)
return FS_ERROR;
for(Cnt = 0; Cnt < MAX_LM_CONNECTIONS; Cnt++)
{
if(g_CreatedClasses.pLMList->GetLMStatus(Cnt, &LMStatus) != FS_SUCCESS)
continue;
if(LMStatus.LMIndex != INVALID_LM_INDEX)
{
memcpy(pLaunchMonInfo, &LMStatus, sizeof(LMStatus));
pLaunchMonInfo++;
(*pNumLaunchMons)++;
MaxLaunchMons--;
if(MaxLaunchMons == 0)
{
return FS_SUCCESS;
}
}
}
return FS_SUCCESS;
}
C#:
[DllImport("FSADLL", SetLastError = false)]
private static extern int FS_GetLMs([Out] IntPtr pLaunchMonInfo, int MaxLaunchMons, ref int pNumLaunchMons);
[StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)] //, Size = 38)]
public struct FS_LMON_STATUS
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = FS_MAX_FIRMWARE_VER)] //10 bytes
public string FirmwareVers;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = FS_MAX_SERIAL_NUM)] // 15 bytes
public string SerialNum;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = FS_MAX_HW_VER)] // 5 bytes
public string HardwareVers;
public uint StatusFlags; //4 bytes
public int LMIndex; // identifies which index //4 bytes
}
const int max_launch_monitors = 8;
FS_LMON_STATUS[] dev_info = new FS_LMON_STATUS[max_launch_monitors];
int num_launch_monitors = 0;
IntPtr pAddr = Marshal.AllocHGlobal(max_launch_monitors * Marshal.SizeOf(typeof(FS_LMON_STATUS)));
Marshal.StructureToPtr(dev_info, pAddr, false);
int result = FS_GetLMs(pAddr, max_launch_monitors, ref num_launch_monitors);
UnityEngine.Debug.Log("Result of FS_GetLMs: " + result);
FS_LMON_STATUS[] device_info = new FS_LMON_STATUS[max_launch_monitors];
//Marshal.Copy(pAddr, device_info, (int)0, num_launch_monitors * (int)Marshal.SizeOf(typeof(FS_LMON_STATUS)));
//Marshal.ReadIntPtr(pAddr, 0);
//device_info = (FS_LMON_STATUS[]) Marshal.PtrToStructure(Marshal.AllocHGlobal(max_launch_monitors * Marshal.SizeOf(typeof(FS_LMON_STATUS[]))), typeof(FS_LMON_STATUS[]));
if (num_launch_monitors > 0)
UnityEngine.Debug.Log("GC2 Device Found.");
else // If there is no devices found, remove the previous device from the holder variable
GC2Device = null;
for (int i = 0; i < num_launch_monitors; i++)
{
device_info[i] = (FS_LMON_STATUS)Marshal.PtrToStructure(pAddr, typeof(FS_LMON_STATUS));
pAddr = new IntPtr(Marshal.SizeOf(typeof(FS_LMON_STATUS)) + pAddr.ToInt64());
}
//*** There will only ever be 1 device in the list until the old SDK is fixed ***
for (int lm_index = 0; lm_index < num_launch_monitors; lm_index++)
{
if (device_info[lm_index].StatusFlags != LM_STATUS_DISCONNECTED)
{
UnityEngine.Debug.Log("device_info.SerialNum: " + device_info[lm_index].SerialNum);
//assign each LM to a LM data structure
LaunchMonitor logical_device = new LaunchMonitor(inst);
logical_device.mLaunchMonitorType = LaunchMonitorType.LAUNCH_MONITOR_TYPE_GC2;
logical_device.mConnectionType = ConnectionType.USB_CONNECTION;
IntPtr pnt = Marshal.AllocHGlobal(Marshal.SizeOf(device_info[lm_index]));
Marshal.StructureToPtr(device_info[lm_index], pnt, false);
//Marshal.Copy(device_info[lm_index], dv_info, 0, (uint)Marshal.SizeOf(typeof(FS_LMON_STATUS)));
logical_device.mConnectionToken = pnt;
//GC2Devices.Add(logical_device);
logical_device.Serial = logical_device.GetSerialNumber();
GC2Device = logical_device;
}
}

Turns out the problem was on the C++ side and all the marshaling stuff was correct. Thanks for the tip Hans.

C# P/Invoke and array of structs containing byte arrays

I need to invoke a native DLL from C# code. As I am not very familiar with C/C++, I can't figure out how a structure defined in C should be declared in C# so it can be invoked. The problem is that two parameters seems to be an array of structs, which I don't know how to declare this in C# (see last code block):
c++ header file:
typedef enum
{
OK = 0,
//others
} RES
typedef struct
{
unsigned char* pData;
unsigned int length;
} Buffer;
RES SendReceive(uint32 deviceIndex
Buffer* pReq,
Buffer* pResp,
unsigned int* pReceivedLen,
unsigned int* pStatus);
c# declaration:
enum
{
OK = 0,
//others
} RES
struct Buffer
{
public uint Length;
public ??? Data; // <-- I guess it's byte[]
}
[DllImport("somemodule.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern uint SendReceive(
uint hsmIndex,
uint originatorId,
ushort fmNumber,
??? pReq, // <-- should this be ref Buffer[] ?
uint reserved,
??? pResp, // <-- should this be ref Buffer[] ?
ref uint pReceivedLen,
ref uint pFmStatus);
in an equivalent java client, i found that the parameter is not just one Buffer but an array of Buffers. In C# it would look like this:
var pReq = new Buffer[]
{
new Buffer { Data = new byte[] { 1, 0 }, Length = (uint)2 },
new Buffer {Data = requestStream.ToArray(), Length = (uint)requestStream.ToArray().Length },
//according to the header file, the last item must be {NULL, 0}
new Buffer { Data = null, Length = 0 }
};
var pResp = new Buffer[]
{
new Buffer { Data = new byte[0x1000], Length = 0x1000 },
//according to the header file, the last item must be {NULL, 0}
new Buffer { Data = null, Length = 0x0 }
};
This seems strange to me because the extern C method does have a pointer to a Buffer struct (Buffer*) and not a pointer to a Buffer array (Buffer[]*).
How do I need to define the Struct in C# and the parameter types of the extern method?
Any help appreciated, Thanks.

Firstly your struct has the parameters in the wrong order. And the byte array needs to be declared as IntPtr with manual marshalling:
struct Buffer
{
public IntPtr Data;
public uint Length;
}
The p/invoke should be:
[DllImport("MyNativeDll.dll", CallingConvention=CallingConvention.Cdecl)]
static extern RES SendReceive(
uint deviceIndex,
[In] Buffer[] pReq,
[In, Out] Buffer[] pResp,
out uint pReceivedLen,
out uint pStatus
);
The byte array needs to be IntPtr so that the struct is blittable. And that's needed so that the array parameters can be declared as Buffer[].
It's going to be a bit of a pain doing the marshalling of the byte arrays. You'll want to use GCHandle to pin the managed byte arrays, and call AddrOfPinnedObject() to get the address of the pinned array for each struct in your arrays of structs. It will be worth your while writing some helper functions to make that task less painful.

Your method signature in c# should be something like:
[DllImport("MyNativeDll.dll")]
public static extern RES SendReceive (uint32 deviceIndex, ref Buffer pReq, ref Buffer pResp, ref uint pReceivedLen, ref uint pStatus);
See this project, it might hel you in the future so generate native calls from .net
http://clrinterop.codeplex.com/releases/view/14120

Based on the C++ header but without testing, have a look at the following code:
using System;
using System.Runtime.InteropServices;
using System.Text;
namespace WindowsFormsApplication1
{
public class Class1
{
public struct Buffer
{
[MarshalAs(UnmanagedType.LPStr)]
public StringBuilder pData;
public uint length;
}
[DllImport("kernel32.dll", EntryPoint = "LoadLibrary")]
static extern int LoadLibrary(string lpLibFileName);
[DllImport("kernel32.dll", EntryPoint = "GetProcAddress")]
static extern IntPtr GetProcAddress(int hModule, string lpProcName);
[DllImport("kernel32.dll", EntryPoint = "FreeLibrary")]
static extern bool FreeLibrary(int hModule);
[UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
internal delegate IntPtr SendReceive(
uint deviceIndex,
ref Buffer pReq,
ref Buffer pResp,
uint pReceivedLen,
uint pStatus);
public void ExecuteExternalDllFunction()
{
int dll = 0;
try
{
dll = LoadLibrary(#"somemodule.dll");
IntPtr address = GetProcAddress(dll, "SendReceive");
uint deviceIndex = 0;
Buffer pReq = new Buffer() { length = 0, pData = new StringBuilder() };
Buffer pResp = new Buffer() { length = 0, pData = new StringBuilder() };
uint pReceivedLen = 0;
uint pStatus = 0;
if (address != IntPtr.Zero)
{
SendReceive sendReceive = (SendReceive)Marshal.GetDelegateForFunctionPointer(address, typeof(SendReceive));
IntPtr ret = sendReceive(deviceIndex, ref pReq, ref pResp, pReceivedLen, pStatus);
}
}
catch (Exception Ex)
{
//handle exception...
}
finally
{
if (dll > 0)
{
FreeLibrary(dll);
}
}
}
}
}

Implementing a custom collation in SQLite for WinRT

I'm trying to implement a custom collation in SQLite for Windows Runtime.
The create_collation method is implemented as follows:
SQLITE_API int sqlite3_create_collation(
sqlite3*,
const char *zName,
int eTextRep,
void *pArg,
int(*xCompare)(void*,int,const void*,int,const void*)
);
So far I have the following C# signature:
[DllImport("sqlite3", EntryPoint = "sqlite3_create_collation", CallingConvention = CallingConvention.Cdecl)]
public static extern int CreateCollation(IntPtr db, [MarshalAs(UnmanagedType.LPStr)] string name, int textRep, object state, Compare callback);
public delegate int Compare(object pCompareArg, int size1, IntPtr Key1, int size2, IntPtr Key2);
This is the implementation:
int i = CreateCollation(db, "unicode_nocase", SQLITE_UTF8, null, CompareMethod);
/* ... */
public static int CompareMethod(object o, int i1, IntPtr s1, int i2, IntPtr s2)
{
return string.Compare(Marshal.PtrToStringUni(s1), Marshal.PtrToStringUni(s2));
}
The application compiles without errors. The call to create_collation returns zero (SQLITE_OK), but if I use the collation in a statement the following error message is returned:
no such collation sequence: unicode_nocase
source reference: https://github.com/doo/SQLite3-WinRT/tree/master/SQLite3Component
Can somebody please help me?
Thank you!

After some time looking around inside Mono.Android.SQLite, which also uses the C implementation of SQLite, I found the solution:
The problem was that the call to sqlite3_create_collation has a void* parameter which I incorrectly defined as object in C# where it should be IntPtr.
I have posted the current implementation I have below. I partially reverse engineered the solution from the Mono implementation, which calls sqlite3_create_collation twice for every collation to be registered - once with the parameter eTextRep set to SQLITE_UTF16LE and a second time with SQLITE_UTF8. I could only imagine that this might help the SQLite core to find a fast implementation for different formats in which the string values are stored. However, these require different decoding when they are converted to C# strings.
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate int CompareCallback(IntPtr pvUser, int len1, IntPtr pv1, int len2, IntPtr pv2);
[DllImport("sqlite3", CallingConvention = CallingConvention.Cdecl)]
private static extern int sqlite3_create_collation(IntPtr db, byte[] strName, int nType, IntPtr pvUser, CompareCallback func);
private const int SQLITE_UTF8 = 1;
private const int SQLITE_UTF16LE = 2;
private const int SQLITE_UTF16BE = 3;
private const int SQLITE_UTF16 = 4; /* Use native byte order */
private const int SQLITE_ANY = 5; /* sqlite3_create_function only */
private const int SQLITE_UTF16_ALIGNED = 8; /* sqlite3_create_collation only */
public void Register(IntPtr db)
{
if (db == IntPtr.Zero)
throw new ArgumentNullException("db");
//create null-terminated UTF8 byte array
string name = Name;
var nameLength = System.Text.Encoding.UTF8.GetByteCount(name);
var nameBytes = new byte[nameLength + 1];
System.Text.Encoding.UTF8.GetBytes(name, 0, name.Length, nameBytes, 0);
//register UTF16 comparison
int result = sqlite3_create_collation(db, nameBytes, SQLITE_UTF16LE, IntPtr.Zero, CompareUTF16);
if (result != 0)
{
string msg = SQLite3.GetErrmsg(db);
throw SQLiteException.New((SQLite3.Result)result, msg);
}
//register UTF8 comparison
result = sqlite3_create_collation(db, nameBytes, SQLITE_UTF8, IntPtr.Zero, CompareUTF8);
if (result != 0)
{
string msg = SQLite3.GetErrmsg(db);
throw SQLiteException.New((SQLite3.Result)result, msg);
}
}
private string GetUTF8String(IntPtr ptr, int len)
{
if (len == 0 || ptr == IntPtr.Zero)
return string.Empty;
if (len == -1)
{
do
{
len++;
}
while (Marshal.ReadByte(ptr, len) != 0);
}
byte[] array = new byte[len];
Marshal.Copy(ptr, array, 0, len);
return Encoding.UTF8.GetString(array, 0, len);
}
private string GetUTF16String(IntPtr ptr, int len)
{
if (len == 0 || ptr == IntPtr.Zero)
return string.Empty;
if (len == -1)
{
return Marshal.PtrToStringUni(ptr);
}
return Marshal.PtrToStringUni(ptr, len / 2);
}
internal int CompareUTF8(IntPtr ptr, int len1, IntPtr ptr1, int len2, IntPtr ptr2)
{
return Compare(GetUTF8String(ptr1, len1), GetUTF8String(ptr2, len2));
}
internal int CompareUTF16(IntPtr ptr, int len1, IntPtr ptr1, int len2, IntPtr ptr2)
{
return Compare(GetUTF16String(ptr1, len1), GetUTF16String(ptr2, len2));
}

C to C# Translation, Calling a WinAPI function: ControlIoDevice

I'm trying to translate some Code written in C to C# (Compact Framework 2.0)
(It's for a Windows CE Device with an RFID Reader).
And in C this system call works fine, but it does not work in C#:
Code In C
HANDLE m_Power =NULL; //<-- This HANDLE is set correctly before call "ControlDevice"
int ControlDevice(int device, BYTE power_state)
{
bool bRet;
DWORD tcBuffer2,dwBytesReturned;
unsigned int a = sizeof(power_state);
bRet=DeviceIoControl( m_Power,
device,
&power_state,
sizeof(power_state),
(PBYTE)&tcBuffer2,
sizeof(DWORD),
&dwBytesReturned,
NULL);
if(bRet)
return 1;
else
return -1;
}
CODE IN C#
int ControlDevice(int device, byte[] power_state)
{
try
{
bool bRet = false;
int bytesReturned = 0;
byte[] tcBuffer2 = new byte[1];
tcBuffer2[0] = 0;
bRet = Device_WinApi.DeviceIoControlCE(m_Power,
device,
power_state,
(int)Marshal.SizeOf(power_state),
tcBuffer2,
(int)Marshal.SizeOf(tcBuffer2),
out bytesReturned,
IntPtr.Zero);
if (bRet)
return 1;
else
{
int LastError = Device_WinApi.GetLastError();
return -1;
}
}
catch (Exception e)
{
return -1;
}
}
The DLL is imported in this way:
[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("coredll.dll", EntryPoint = "DeviceIoControl", SetLastError = true)]
internal static extern bool DeviceIoControlCE(
IntPtr hDevice,
long dwIoControlCode,
byte[] lpInBuffer,
int nInBufferSize,
byte[] lpOutBuffer,
int nOutBufferSize,
out int lpBytesReturned,
IntPtr lpOverlapped);
In the current implementation in C#, bRet = false, and I should be true, as this is the value obtained in C
this return zero too:
int LastError = Device_WinApi.GetLastError()
Any help will be really appreciated!
Thank you advance for your time!!