PInvoke

[grndvl1]

Here is my issue, I am very new to C# and want to invoke a custom dll that I can't register using regsvr32. I figured out I need to use PInvoke somehow but need help since all the methods return void, the data is in the Msg pointer. Some of the functions will need to send data using Msg and then will receive back in a modified pointer.

Here is one example the message is a structure that is passed to GetTMVersionInfo ( TM_Message* Msg ) and by sending a blank message it will modify the TM_Message pointer with the real data. The dll is for a keyboard I need to write drivers to, a Bosch Intuikey.


typedef struct
{
BYTE Msg[MAX_MSG_LEN];
int MsgLen;
} TM_Message;

TM_Message will be used as an output parameter for all API’s. All API’s will return the formed packet in
TM_Message structure.
• Msg will be the framed packet.
• MsgLen will be the length of packet.
• MAX_MSG_LEN is a macro, having value 80.


void GetTMVersionInfo ( TM_Message* Msg )
This API will be used to form packet for information message “Get_Version”. Formed packet will return in output parameter TM_Message.
Input Parameters: None
Return Type: Void

remember I am new to C# and not good at C, been a while so type slowly so I can understand :-)

Thanks
John

[Dheeraj Joshi]

void GetTMVersionInfo ( TM_Message* Msg )
 

Are you changing the value of *Msg in this function.?

Regards
Dheeraj Joshi

[grndvl1]

Actually i found the answer here it is

[StructLayout(LayoutKind.Sequential)]
public struct TM_Message {
[MarshalAs(UnmanagedType.ByValArray, SizeConst = ConstantsUsed.MAX_MSG_LEN)]
public byte[] data;
public int MsgLen;
};

public static class ConstantsUsed {
public const int MAX_MSG_LEN = 80;
}

and then make the dll calls

[DllImport("terminalModeDll.dll")]
private static extern void GetTMVersionInfo(ref TM_Message msg);

and then make a generic method wrapper to do any processing:

public TM_Message m_GetTMVersionInfo(TM_Message message) {
GetTMVersionInfo(ref message);
return message;
}