Use C++ DLL from C# Code

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I have a c++ dll file that i need to use from a c# project.
This dll file is for a machine connected through a usb port. It contains some functions that i want to use "MA_Initialize(HWND pwndDest, UINT nComMsg)" it initializes the MA usb communication handler.
1. pwndDest :Handle to user’s window whose window procedure will
receive the message from communication handler.
2. nComMsg :Specifies the user defined message to be received.

How can I create the handle to this function, and how can I use it??

Posted 29-Jun-14 22:01pm

Member 10866132

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George Jonsson · Answer 1 · 2014-06-29T22:27:00

Solution 1

You need to use PInvoke.

This is a good website you can use as reference www.pinvoke.net

C#

[DllImport("YourDLL name"]
public static extern int MA_Initialize(IntPtr pwndDest, uint nComMsg);

You don't mention the return type so I assumed an int.

You can then get the handle from the Form like this.

C#

IWin32Window formHandle = this;       // this refers to the form
MA_Initialize(formHandle.Handle, 0);  // 0 is just an example value.

Posted 29-Jun-14 22:27pm

George Jonsson

Updated 29-Jun-14 22:35pm

v2

Comments

Member 10866132 30-Jun-14 4:37am

The return type is boolean. I know this Import code, what I need to know is about "pwndDest", how to create it and then call MA_Initialize?

Member 10866132 30-Jun-14 4:46am

Can I create a simple handle and use it instead of formHandle.Handle? If it is possible could you make a small example about creating and using this handle.
Thank you

George Jonsson 30-Jun-14 5:13am

Why doesn't the solution work?
Don't you have a Windows Form in your application? (I got that impression)

Member 10866132 30-Jun-14 6:20am

It works, I just want to do some calculation when something happens.
How can I put a code in the handler function?

George Jonsson 30-Jun-14 7:24am

Not sure what you want to achieve. What do you mean by handler function?

George Jonsson 30-Jun-14 7:22am

I don't know how MA_Initialize works, but from the look of it the handle to the user window is used for posting messages to the message loop.
I have never created a window less message loop, but I guess you can look into Application.DoEvents();

Member 10866132 30-Jun-14 7:31am

The user’s program should call MA_Initialize to start the MA usb
device communication handler. Then, this communication handler will continuously
watch if there is any supported MA device connected to or removed from the current
computer. Besides, all the data sent from MA device would be decoded by this
communication handler first and stored in its own memory stack. User’s program can
get all the notifications from MA usb communication handler by user defined message at
user’s own window handle.