Error: Calling C++ dll function in C# - C# Discussion Boards

Re: How to Send & Receive data using USB port in C#

22-Oct-12 5:07

You can treat them as Serial port (see my example I added as answer). But indeed it is very cause-dependent if you can use them as serial port or not.
I use USB as serial port in my Arduino-Example[^] and it turned out working well Wink | ;-)

. Please tell me if I am wrong...

Dave Kreskowiak22-Oct-12 10:25

Dave Kreskowiak

22-Oct-12 10:25

Marco Bertschi wrote:
You can treat them as Serial port

PROVIDED you have a driver that exposes a device as a serial port. It does not convert the USB port to a Serial port. Why? Because you can drop a USB hub in between the Arduino and the computer and your Arduino will still work as a serial device and the USB port will still work with other non-serial devices attached to the same hub.

You're using the USB port, actually bus, to communicate with a device that is exposed as a serial device. You did not treat the USB port as a serial port. USB is mearly supplying the transport mechanism carrying your serial protocol.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak

Re: How to Send & Receive data using USB port in C#

Marco Bertschi22-Oct-12 21:35

Re: How to Send & Receive data using USB port in C#

22-Oct-12 21:35

Ooops. off course, I totally forgot that I had to install a driver for the Arduino board before I was able to use it D'Oh! | :doh:

Nevermind

Marco Bertschi22-Oct-12 5:02

Re: How to Send & Receive data using USB port in C#

22-Oct-12 5:02

willington.d wrote:
How to do this in c#? Is there any Namespase or thrd party dll available?

You can use the SerialPort class which is available in the namespace System.IO.Ports.

You need the following variables to initialize a serial port (you can treat the USB port as a serial port).

private SerialPort _port;       //Serial port (USB)
const int BAUDRATE = 9600;      //Baud-Rate of the serial port (must be the same value on the other device)
const string COMPORT = "COM8";  //Name of the port
delegate void DisplayArduinoSerialOutput(string arduinoSerialOutput); //Delegate to display the serial input buffers' content to the User

In the constructor of your App, you need to call the following method to initialize your serial port:

/// <summary>
/// This method initializes the COM-Port
/// </summary>
private void InitCOMPort()
{
   _port = new SerialPort(COMPORT) { BaudRate = BAUDRATE };
   //Event occurs when any data arrives at the port
   _port.DataReceived += new   SerialDataReceivedEventHandler(_port_DataReceived); 
   //Open the port 
   //An exception can rise if another program blocked
   //the port
   _port.Open();
}

Afterwards, your port is ready to use:

/// <summary>
/// Occurs when new data is available at the ports input buffer
/// </summary>
/// <param name="sender">the sender of the event (usually the port)</param>
/// <param name="e">Some event args, not used at the moment</param>
private void _port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
   DisplayArduinoSerialOutput displayArduinoSerialOutput = new DisplayArduinoSerialOutput(arduinoSerialOutputTextBox.AppendText);
   SerialPort spL = (SerialPort)sender;
   this.Dispatcher.Invoke(displayArduinoSerialOutput, spL.ReadExisting());
}

In my case, I invoke the UI to add the data to a text box using the Delegate located near my other variables.

Please note: Maybe you have to change the piece of code in the _port_DataReceived-Eventhandler (because I used WPF for this snippet).

However, hope I was able to answer your question.

Richard Andrew x6422-Oct-12 7:48

Richard Andrew x64

22-Oct-12 7:48

Forgive me if you've answered this already, but what would be the name of the port when using the USB?

Marco Bertschi wrote:
const string COMPORT = "COM8";

The difficult we do right away...
...the impossible takes slightly longer.

Re: How to Send & Receive data using USB port in C#

Marco Bertschi22-Oct-12 21:43

Error: Calling C++ dll function in C#

22-Oct-12 21:43

Uhh, yes, Dave Kreskowiak remembered me about something: You need a driver which exposes the USB as serial ports to your computer (My fault, I am sorry for this one).

Imagine, every Serial Port has its name. In my case, they are numbered from "COM1", "COM2", [...], "COM8", "COMx". I am unsure if this naming is a standard or if it is driver-specific, you might need to do some further research on this naming thing...

However: detecting available COM ports is not that difficult, I found some information about that on Codeproject[^] and on Stackoverflow.com[^]. I'm not sure if this fits your needs, but have a look at it.

Cheers
Marco

taibc21-Oct-12 17:33

21-Oct-12 17:33

Hi,

I am trying to use functions in C++ dll from C#, but I got an error: "attempt to read or write protected memory. This is often indication that other memory is corrupt"
Anyone know how to fix ?

Here is C++ functions:

typedef void *DGNHandle;

 __declspec(dllexport) DGNHandle CPL_DLL    DGNOpen( const char *, int );
 __declspec(dllexport) DGNElemCore CPL_DLL *DGNReadElement( DGNHandle )

Here is structure in C++:

typedef struct {
    int         offset;
    int         size;

    int         element_id;     /*!&lt; Element number (zero based) */
    int         stype;          /*!&lt; Structure type: (DGNST_*) */
    int         level;          /*!&lt; Element Level: 0-63 */
    int         type;           /*!&lt; Element type (DGNT_) */
    int         complex;        /*!&lt; Is element complex? */
    int         deleted;        /*!&lt; Is element deleted? */

    int         graphic_group;  /*!&lt; Graphic group number */
    int         properties;     /*!&lt; Properties: ORing of DGNPF_ flags */
    int         color;          /*!&lt; Color index (0-255) */
    int         weight;         /*!&lt; Line Weight (0-31) */
    int         style;          /*!&lt; Line Style: One of DGNS_* values */

    int         attr_bytes;     /*!&lt; Bytes of attribute data, usually zero. */
    unsigned char *attr_data;   /*!&lt; Raw attribute data */

    int         raw_bytes;      /*!&lt; Bytes of raw data, usually zero. */
    unsigned char *raw_data;    /*!&lt; All raw element data including header. */
} DGNElemCore;

And below converted codes are in C#:

[StructLayout(LayoutKind.Sequential )]
    public class DGNElemCore
    {
        public int attr_bytes;
        public byte[] attr_data;
        public int color;
        public int complex;
        public int deleted;
        public int element_id;
        public int graphic_group;
        public int level;
        public int offset;
        public int properties;
        public int raw_bytes;
        public byte[] raw_data;
        public int size;
        public int style;
        public int stype;
        public int type;
        public int weight;

    }

[DllImport("DgnLib.dll", EntryPoint = &quot;DGNOpen&quot;)]
        public static extern IntPtr  DGNOpen(string fileName, int bUpdate);
[DllImport("DgnLib.dll", EntryPoint = "DGNReadElement")]
        public static extern DGNElemCore DGNReadElement(IntPtr DGNHandle)

Codes for testing:

DGNElemCore element = new DGNElemCore();
element = DgnFile.DGNReadElement(dgnFile.oDgnFile)

Richard MacCutchan21-Oct-12 21:59

21-Oct-12 21:59

The error message is quite clear about what went wrong, but you will need to use your debugger to track down exactly where it occurs.

One of these days I'm going to think of a really clever signature.

taibc21-Oct-12 22:01

21-Oct-12 22:01

Hi,

It throwed error at the last line: element = DgnFile.DGNReadElement(dgnFile.oDgnFile)

Richard MacCutchan21-Oct-12 22:55

21-Oct-12 22:55

As I said before, you need to use your debugger to find out what is happening. There is no way we can guess what is going on inside the program.

One of these days I'm going to think of a really clever signature.

taibc21-Oct-12 23:28

21-Oct-12 23:28

Thank you.

But, the exception window only show that messeage. And, the below is output from debug:

Quote:
A first chance exception of type 'System.AccessViolationException' occurred in mscorlib.dll
The thread 'vshost.RunParkingWindow' (0x518) has exited with code 0 (0x0).
The thread '<no name="">' (0x1fdc) has exited with code 0 (0x0).
The program '[7952] CLCLis.vshost.exe: Managed (v2.0.50727)' has exited with code 0 (0x0).
The program '[7952] CLCLis.vshost.exe: Program Trace' has exited with code 0 (0x0).

I still haven't found the reason for this error

Richard MacCutchan21-Oct-12 23:34

21-Oct-12 23:34

Well it looks as if some code is passing a bad pointer to a function in mscorlib.dll. Where does this DLL come from, is it your code or from a third party? If the latter then contact the people who wrote it and ask for assistance.

One of these days I'm going to think of a really clever signature.

taibc21-Oct-12 23:40

21-Oct-12 23:40

Thank you.

I used Visual Studio (project type: win 32 console application) to create this dll file from a C++ files collection (.h and .cpp) of a third-party (Here is the link of source code: http://dgnlib.maptools.org/dl/dgnlib-1.11.zip )

Richard MacCutchan21-Oct-12 23:41

21-Oct-12 23:41

Since you have the source code you can step through it in your debugger to trace the error.

One of these days I'm going to think of a really clever signature.

taibc21-Oct-12 23:45

21-Oct-12 23:45

How I can trace the error through source codes while I am using dll file ? and I think the source codes don't have error, because I still can use it in Visual C++, but I got the error while trying in C#

Richard MacCutchan22-Oct-12 0:08

22-Oct-12 0:08

taibc wrote:
How I can trace the error through source codes while I am using dll file ?

Just the same, build a debug version of the DLL and the debugger should be able to step into it.

taibc wrote:
I think the source codes don't have error

That may well be true, but only by extensive testing can you be sure.

One of these days I'm going to think of a really clever signature.

Richard MacCutchan22-Oct-12 0:10

22-Oct-12 0:10

I have just looked again at the layout of your C++ and C# structures; why are they different?

One of these days I'm going to think of a really clever signature.

J4amieC22-Oct-12 0:25

J4amieC

22-Oct-12 0:25

The OP has laid them out alphabetically in c#, im pretty sure this will be the issue, non?

Richard MacCutchan22-Oct-12 1:05

22-Oct-12 1:05

True; I did not check that originally, it never occurred to me that anyone would think of doing such a thing. D'Oh! | :doh:

One of these days I'm going to think of a really clever signature.

taibc22-Oct-12 0:37

22-Oct-12 0:37

I only convert the field type: unsigned char * (in C) into byte[] (in C#)

Richard MacCutchan22-Oct-12 1:03

22-Oct-12 1:03

Yes but you have moved the elements into different positions within the structure. How can that work?

One of these days I'm going to think of a really clever signature.

BobJanova22-Oct-12 4:20

BobJanova

22-Oct-12 4:20

This isn't my area but:

Defining the fields in the struct in a different order definitely won't work. You need to declare in the same order (hopefully the reason for this is obvious).
You've defined it as a class in C#, not a struct. I think you need it to be a struct, even though it's a pointer type declaration in C++. You might even need to declare it IntPtr and use Marshal methods to make a struct out of it.
What is DGNHandle? That C++ function definition isn't valid unless it's a macro.

taibc22-Oct-12 15:51

22-Oct-12 15:51

Thanks BobJanova and Richard MacCutchan very much.

I changed the order of fields and using "struct" instead of "class" in C#. DGNHandle is "Opaque handle representing DGN file, used with DGN API"

Now, I got another error: Exception of type 'System.ExecutionEngineException' was thrown.

Please see my detail codes:

[DllImport("DgnLib.dll", EntryPoint = "DGNReadElement")]
        public static extern IntPtr DGNReadElement(IntPtr DGNHandle);

        public static DGNElemCore ReadElement(IntPtr DGNHandle)
        {

            DGNElemCore element = new DGNElemCore ();
            IntPtr itr = DGNReadElement(DGNHandle);

            element = (DGNElemCore)Marshal.PtrToStructure(itr, typeof(DGNElemCore)); // throw the exception

            return element;

        }

I am wondering: Can I convert a structure pointer (DGNElemCore *) in C to IntPtr (in C#), then use Marshal to get DGNElemCore. The function in C is:

C++

__declspec(dllexport) DGNElemCore CPL_DLL *DGNReadElement( DGNHandle );

Thank you very much !

taibc22-Oct-12 16:43