Question

I am trying to import a function from a c dll into C#. The c function looks like this

unsigned short write_buffer( unsigned short device_number, unsigned short word_count, unsigned long buffer_link, unsigned short* buffer)

my attempt at a C# import looks like this

[DllImport("sslib32.dll", CharSet = CharSet.Ansi, SetLastError = true)]
private static extern ushort write_buffer(ushort deviceNumber, ushort wordCount, UInt32 bufferLink, IntPtr buffer)

In C# i have a Dictionary of messages that i would like to pass to this function. The Dictionary looks like this:

Dictionary<string, List<ushort>> msgs

I am a bit confused how to make a make a proper call to pass msgs as the buffer. deviceNumber is 2, wordCount is 32, and buffLink is 0. So i know the call should look something like this

write_buffer(2,32,0, msgs[key]);

Obviously i am getting an invalid argument for the IntPtr. What is the proper way to make this call?

Answer 1

It is quite unclear what buffer should contain and in which direction its data flows. Your dictionary suggests it should be an array. Just declare it that way:

 private static extern ushort write_buffer(.., ushort[] buffer);

And use msgs[key].ToArray() in the call.

Using constants in the write_buffer() call does not make that a likely scenario though, there ought to be msgs[key].Count in there somewhere.