Code to Export C# DLL to Metatrader

Note: updated build 600+ code can be found at Code to Export C# DLL to Metatrader Build 600+.

I worked up a simple sample C# DLL that is properly exported for use with Metatrader. I made use of the template that can be downloaded from C# Project Template for Unmanaged Exports.

C# Code for "testUMD.dll" below using R. Giesecke's template:

Code:

using System;
using System.Text;
using RGiesecke.DllExport;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace testUnmanagedDLL
{
   class Test
   {
 
        [DllExport("AddInteger", CallingConvention = CallingConvention.StdCall)]
        public static int AddInteger(int Value1, int Value2) {
            MessageBox.Show("Add Integers: " + Value1.ToString() + " " + Value2.ToString());
            return (Value1 + Value2);
        }

        [DllExport("AddDouble", CallingConvention = CallingConvention.StdCall)]
        public static double AddDouble(double Value1, double Value2) {
            MessageBox.Show("AddDouble: " + Value1.ToString() + " " + Value2.ToString());
            double Value3 = Value1 + Value2;
            return (Value3);
        }

        [DllExport("AddDoubleString", CallingConvention = CallingConvention.StdCall)]
        public static string AddDoubleString(double  Value1, double Value2) {
            MessageBox.Show("AddDoubleString: " + Value1.ToString() + " " + Value2.ToString());
            double Value3 = Value1 + Value2;
            return (Value3.ToString() );
        }

        [DllExport("returnString", CallingConvention = CallingConvention.StdCall)]
        public static string returnString(string Input) {
            MessageBox.Show("Received: " + Input);
            return ("SEND to MT4");
        }

        // many thanks to anonymous for the code sample below!
        [DllExport("ReturnDouble2", CallingConvention = System.Runtime.InteropServices.CallingConvention.StdCall)]
        static double ReturnDouble2() {
            return 4.5;
        }

   }

MT4 Script 'testDLL' code below: File testUMD.dll added to experts/libraries folder

Code:

#import "testUMD.dll"
   int AddInteger(int Value1, int Value2);
   double AddDouble(double Value1, double Value2);
   string AddDoubleString(double Value1, double Value2);
   string returnString(string Input);
   double ReturnDouble2(); 
#import
//+------------------------------------------------------------------+
//| script program start function                                    |
//+------------------------------------------------------------------+
int start()
  {
//----
   Print("AddInteger: " + AddInteger(250, 750));
   double a = AddDouble(250,750);
   Print("AddDouble: " + NormalizeDouble(a,4));

   double d = StrToDouble(AddDoubleString(250, 750));
   Print("AddDoubleString: " + NormalizeDouble(d,4));
   string temp = "Send to DLL";
   string recv = returnString(temp);
   Print(recv);
   double dd = ReturnDouble2();
   Print("Returning Double from C#: " + NormalizeDouble(dd, 4));
//----
   return(0);
  }

Cursory Summary: Integer passing = success, double passing MT4 to C# = success, double passing from C# to MT4 = fail, string passing = success. I haven't experimented with arrays. Sample code written with VS 10 .NET 4.0.

If anyone knows how to successfully get doubles to pass from C# to MT4 without conversion to a string, please leave a comment!

------------

Edit: thanks for the feedback from anonymous! The code has been updated to reflect passing a double from C# to Metatrader.

By the way, you must use the 32 bit version of the DLL. The 64 bit version and the "Any CPU" version both failed with error #127 in Metatrader. This is understandable considering MT4 is a 32 bit program. 

As per g3ro's suggestion I have made available for download both the testUnamanagedDLL Visual Studio solution and the testDLL MT4 script. Download testUnmanagedDLL VS solution