working with pointers from an ocx control in c# csharp

Question

Edit: I'm working with an ocx control in C#. This contrl has properties which contain the length of a data buffer and a pointer to that buffer. How can access/get/use that data with possibly a point in C#. I'm using Visual Studio 2008.

~~i work with .ocx control in c#. That .ocx have a properties which contains len of data buffer and pointer to data buffer. How i can get data, using that pointer in c#? I use VS C# 2008~~

It is all about Marshalling. Could you please provide the C/Pascal definition of the function that you are calling. From that I will provide you with the correct C# function definition — Richard Schneider
– Richard Schneider, Commented Feb 14, 2011 at 8:34
.ocx have function: Public Function WriteData(ByVal devIndex As Long, ByVal lpOutData As Long, ByVal cntData As Long) As Long. How can i call this method? Also ocx have: event Public Event DataArrival(ByVal devIndex As Long, ByVal lpDataBufer As Long, ByVal lenDataBufer As Long). In c# this event: private void AX_DataArrival(object sender, AxUSBBridge.__FT245R_DataArrivalEvent e), the e variable have devIndex, lenDataBufer, lpDataBufer properties. lenDataBufer is size of buffer, lpDataBufer is pointer to data array. How to get buffer? — Xaver
– Xaver, Commented Feb 14, 2011 at 9:29

Daniel Rose · Accepted Answer · 2011-02-14 10:23:35Z

3

You didn't give exact details, so this is a guess based on your info. You can find an example here. I'll quote (and simplify) the relevant parts:

// C/C++
int ncWrite(unsigned long DataSize, void* DataPtr)

// C#
[DllImport("Nican.dll")]
unsafe static extern int ncWrite(uint DataSize, byte[] DataPtr);

byte[] DataWrite = {0x23, 0x23, 0x30, 0x03, 0x78, 0xEC, 0xFF, 0xFF };
int status = ncWrite(Marshal.SizeOf(DataWrite), DataWrite);

EDIT: With your info:

// .ocx
Public Function WriteData(ByVal devIndex As Long, ByVal lpOutData As Long, ByVal cntData As Long) As Long

// C#
[DllImport("TheOcxControl.dll")]
static extern int WriteData(int index, byte[] outputData, int outputDataLength);

byte[] DataToWrite = {0x23, 0x23, 0x30, 0x03, 0x78, 0xEC, 0xFF, 0xFF };
int status = WriteData(index, DataToWrite, Marshal.SizeOf(DataToWrite));

As for the arrival event:

// the e variable have devIndex, lenDataBufer, lpDataBufer properties.
// lenDataBufer is size of buffer, lpDataBufer is pointer to data array.
byte[] destination;
Marshal.Copy(lpDataBufer, destination, 0, lenDataBufer);

edited Feb 14, 2011 at 10:23

answered Feb 14, 2011 at 7:30

Daniel Rose

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3 Comments

Richard Schneider Over a year ago

Good inference. But we do not know if the buffer is Input or Output.

Xaver Over a year ago

how can i Use DllImport if i use ocx? i add that on my toolbox and drop on form, and all import took place automatically? for arrival event error: The best overloaded method match for 'System.Runtime.InteropServices.Marshal.Copy(int[], int, System.IntPtr, int)' has some invalid arguments. Have you a good article about Marshaling and IntPtr in c#?

Daniel Rose Over a year ago

Where did you get the "public function..." part? I haven't used ocx controls, so I don't know how it shows up in your project. As for the Marshal.Copy(), I assumed you would use this overload: msdn.microsoft.com/en-us/library/ms146631.aspx

Community · Accepted Answer · 2017-05-23 11:55:44Z

0

check this one out. How can I pass a pointer to an array using p/invoke in C#?

edited May 23, 2017 at 11:55

CommunityBot

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answered Feb 14, 2011 at 7:27

Mubashir Khan

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