Hello, i'm a new in C#. i currently venturing in software controlling a hardware area. I have an I/O card which fixed into my PC. This I/O card has relay so that it can control the machines when connected.

This I/O card came with the driver and DLL file.
the problem i'm facing now is how to open and read the dll file? once open, how am i gonna control the I/O using C#?
thanks in advanced!

If the DLL is accessible through standard COM then you just need to add a reference to it from your .net application.

If you are using Visual Studio then you just a reference to the COM DLL and VS will create the runtime callable COM wrapper around the COM DLL. Then you program against the DLL's api just as if it were a .NET reference. Technically it IS a .NET reference, it's just a reference to a .NET assembly that handles the plumbing to talk to the COM DLL.

If you aren't using Visual Studio, you'll need to use the tlbimp program that comes with the framework (I think, it might be part of the framework SDK). This will create the runtime callable wrapper you need to talk to COM.

-Peter

yes i'm using VS to call the DLL. Well, i still have problems bout the reference thing. Maybe u can help me with this. I'm using c#.
here's the code to import the DLL.

class call_dll {

  [StructLayout(LayoutKind.Sequential, Pack=1)]
  private struct STRUCT_DLL {
    public short port;
    public short bit;
    public state;

  }

  [DllImport("ASA32.dll")]
  private static extern int func_dll(int DevOpen, ref STRUCT_DLL s);
}

then later i create a button to call and do the function of this 'func_dll' from ASA32.dll

upon clicking the button, i write this code.

int open;

call_dll.STRUCT_DLL mystruct = new STRUCT_DLL();

mystruct.port = 0;
mystruct.bit = 1;
mystruct.state = 1;

unsafe
{
int ret=call_dll.func_dll(&open, ref mystruct);
MessageBox.Show("This is "+ ret);
}

When i click the button, i should have the value in ret is 0. Instead, i only have the address of ret which is 2072613118...something like this. The problem i suspect is that i never pass those port =0, bit =1 and state =1 values into ret. pls help me.
thanks

seems like nobody care about me. what type of forum is this? dead or alive no one knows.

This forum is very alive...

Perhaps the problem is that the people on it (myself included) have not done work like this so we can not answer the question further.

Does the device you are trying to interface have a manufacturer web site with some help on it? Perhaps a manual?

-Peter