Return C# struct to MQL via DLL

[Hendrik Piiriste]

Hi,

I would expect the following code to work. But MQL giving "'Order' - illegal returned type".

Any idea why?

C#

namespace ExpertAdvisor
{
    public class ExpertAdvisor
    {
        [DllExport]
        public static Order Order()
        {
            Order Order = new Order();
            Order.IsBuy = true;
            Order.IsSell = false;
            Order.TakeProfit = 100;
            Order.StopLoss = 50;

            return Order;
        }
    }

    StructLayout(LayoutKind.Sequential, Pack = 1)]
    public struct Order
    {
        public bool IsBuy;
        public bool IsSell;
        public double TakeProfit;
        public double StopLoss;
    }
}

MQL

  struct order
    {
        bool isBuy;
        bool isSell;
        double takeProfit;
        double stopLoss;
    };

#import "ExpertAdvisor.dll"
order Order();
#import

//|                                                                  |
//+------------------------------------------------------------------+
int OnInit()
  {
   return(INIT_SUCCEEDED);
  }
//+------------------------------------------------------------------+
//| Expert deinitialization function                                 |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
  {
  }
//+------------------------------------------------------------------+
//| Expert tick function                                             |
//+------------------------------------------------------------------+
void OnTick()
  {
  
      order test = Order();

  }

Best Regards,

Hendrik

[amrali]

lastpunisher:

Hi,

I would expect the following code to work. But MQL giving "'Order' - illegal returned type".

Any idea why?

Best Regards,

Hendrik

Try to pass a ref to the structure

[Dominik Egert]

Because MQL supports only fundamental types as return values.

You need to use pointers in c# and references in MQL as function parameters.

[Mahrukh Aleem]

Convert structure to string and then send string, receive string convert back to structure.

[Dominik Egert]

Converting to string is inconsistent. Do not use strings for binary data.

Strings have a stop byte. It won't work due to length detection issues.

[Hendrik Piiriste]

amrali #:
Try to pass a ref to the structure

Could you give me an example? As I'm not sure how to do that.

[Hendrik Piiriste]

Dominik Egert #:

Because MQL supports only fundamental types as return values.

You need to use pointers in c# and references in MQL as function parameters.

My concert is the return type of the DLL, but MQL complains when using struct as DLL return type.