Calling named pipes dll from MT5. How to?

#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);
#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);
//----
   return(0);
  }

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");
        }

   }
}

Quoting Jasonforex

Disliked

FXEZ,

I am making a little progress. I have been able to call a simple function like you've shown but opening a named pipe is still not working right now. I did switch from RGiesecke's method of exporting to Selvin's (link). Both are similar but I found Selvin's method a little easier to get working. The solution includes the files necessary to build the .exe and the dependent dll. My progress is on GitHub (link)...

Ignored

[DllExport("SetPipeName", CallingConvention.StdCall)]
static bool SetPipeName([In, MarshalAs(UnmanagedType.LPWStr)] [b][u]StringBuilder[/u][/b] name)
{
     PipeName = name.ToString();
     return true;
}

private static string _serverName;
public static string ServerName
{
     [return: MarshalAs(UnmanagedType.LPWStr)]
     get { return _serverName; }
     set { _serverName = value; }
}

[DllExport("UpdatePipeName", CallingConvention.StdCall)]
static string UpdatePipeName([In, [b][u]Out,[/u][/b] MarshalAs(UnmanagedType.LPWStr)] StringBuilder name)
[return: MarshalAs(UnmanagedType.LPWStr)]
{
     PipeName = name.ToString();
     return PipeName;
}