Question

I am currently working on a at an IT company. They made their software using Clarion,
and in that software they have a DLL which recalculates a lot of values from their database. I need to call this DLL from my C# project. I tried everything without it working.

My code is as below:

public partial class Form1 : Form
{
    [DllImport("EPNORM.dll", EntryPoint = "MyRecalcualate@FlOUcOUcOsbOUc")]
    public static extern void MyRecalcualate(System.Int64 myPtr, System.Int64 myLong, CWByte myByte);

    [DllImport("User32.dll")]
    public static extern Boolean MessageBeep(UInt32 beepType);

    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        System.Int64 myPtrTemp = 1234;
        System.Int64 myLongTemp = 5678;
        System.Byte myByteTemp = 88;

        try
        {
            MyRecalcualate(myPtrTemp, myLongTemp, myByteTemp);
            bool messagebeep = MessageBeep(1);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
        finally
        {
            MessageBox.Show("Successful");
        }
    }
}

The problem is when I call it with breakpoints, it just disappears into the MyRecalcualate method and reaches the finallly block after 2 seconds and re-displays without doing anything from the DLL. Is this because there is something in the DLL method I need to fix or because I am doing the call wrong?

The parameters to the call below is : MyRecalculate(LONG, LONG, BYTE)

MyRecalcualate      PROCEDURE (MyStringPtr, MyLong, MyByte) ! Declare Procedure
LOC:CString         CSTRING(255)
LOC:Byte            BYTE
CODE
! clear completely LOC:CString with null values
LOC:CString = ALL('<0>', SIZE(LOC:CString))

! load string value, byte by byte, from memory address passed (MyStringPtr) and put into LOC:CString
I# = 0
LOOP
     PEEK(MyStringPtr + I# , LOC:Byte)
     IF LOC:Byte = 0 THEN BREAK END
     LOC:CString[I# + 1] = CHR(LOC:Byte)
     I# += 1
END

MESSAGE('MyString value is:||' & CLIP(LOC:CString))
MESSAGE('MyLong value is:||' & MyLong)
MESSAGE('MyByte value is :||' & MyByte)

This is the screenshot their contracted developer mailed me of the parameters and how he calls it in VB.NET:
VB.NET CODE: http://imageshack.us/photo/my-images/269/callfromvisualbasictocl.jpg/
PARAMETERS IN CLARION: http://imageshack.us/photo/my-images/100/asdxg.jpg/

Answer 1

The first parameter is a pointer to a null-terminated character string. You can’t just pass a random Int64 value. So your pinvoke should look like this:

[DllImport("EPNORM.dll", EntryPoint = "MyRecalcualate@FlOUcOUcOsbOUc")]
public static extern void MyRecalcualate(string myPtr, int myInt, byte myByte);

I believe that the second parameter, the Clarion LONG, is a 32 bit integer. So int on the C# side. What’s more, you need to double check the calling convention on the Clarion side. Are you sure it is stdcall which is what your C# uses.