How to call delphi dll's pointer type from C#?

Question

//delphi code

procedure SendData(data:pointer;size:cardinal); stdcall;
   begin
    c.SendData(data,size);
   end;

  function GetEvent(out tag:cardinal):integer; stdcall;
   begin
    result:=0;
    if qEnd<>qStart then begin
     result:=queue[qStart].eventCode;
     tag:=queue[qStart].eventTag;
     inc(qStart);
    end;
   end;

  function GetMessage(handle:cardinal;out data:pointer):cardinal; stdcall;
   begin
    result:=GetMsg(handle,data);
   end;

---

I am using unity3d engine, using c# from it. And I need to integrate and call dll file created from delphi.

So I wrote in c#,

using UnityEngine;
using System.Collections;
using System; 
using System.Text; 
using System.Collections.Generic; 
using System.Runtime.InteropServices;

public class test : MonoBehaviour {
    [DllImport ("ServerTool")]
    private static extern void Connect(int a);
    [DllImport ("ServerTool")]
    private static extern int GetEvent();
    [DllImport ("ServerTool")]
    private static extern void SendData(IntPtr p,  int b);

    // Use this for initialization
    void Start () {
        Connect(0);

        SendData("asdf", 1);
        Debug.Log(GetEvent());
    }

    // Update is called once per frame
    void Update () {

    }
}

This occur errors says,

Assets/test.cs(20,17): error 1502: The best overloaded method match for test.SendData(System.IntPtr, int) has some invalid arguments Assets/test.cs(20,17): error 1503: Argument /#/1 cannot convert string expression to type `System.IntPtr'

I don't know well about delphi, but pointer is similar c#'s object, isn't it? So I tried to change IntPtr to object, then compiling is done, but when run the code, error appears,

MarshalDirectiveException: Marshalling of type object is not implemented test.Start () (at Assets/test.cs:20)

Then how can I call above's delphi's SendData function from c#?

Thanks.

Answer 1

You have to use the Marshaling of C#:

In your case you have to convert the String to an IntPtr with Marshal.StringToHGlobalAnsi, which takes a string parameter and returns an IntPtr.

See the MSDN Documentation:

http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.marshal.stringtohglobalansi.aspx

As mentioned from David you also have to use FreeHGlobal.

Answer 2

The pointer type should be OK. Your integer is wrong. A cardinal in Delphi is a 32bit long unsigned integer (0 through 4294967295). DocWiki Reference