Calling Fortran dll from C#

[jhlee0301]

Hello guys.

I am familiar with C# but need to import Fortran class library. Not expert in Fortran.

This is most popular example in google but I cannot run it.

Dll_test1.dll is located in bin\Debug of C# project.

When executing debug, there occurs format exception error.

My environment is Visual Studio 2019 and Intel Parallel Studio XE 2020.

I think I miss something in compiler environment.

Please help me to find the solution.

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

Fortran

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

FUNCTION TSAT11(P)

REAL, INTENT(IN) :: P
REAL :: TSAT11
! Examle calculation
TSAT11 = P - 273.15
RETURN
END FUNCTION

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

C#

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

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
   public static class FortranLib
   {
      private const string _dllName = "Dll_test1.dll";

      [DllImport(_dllName, CallingConvention = CallingConvention.StdCall)]

      public static extern float TSAT11(float P);
   }

   public partial class Form1 : Form
   {

      public Form1()
      {
         InitializeComponent();
      }

      private void btnDoIt_Click(object sender, EventArgs e)
      {
         float p = 300f;

         float t = FortranLib.TSAT11(p);      //<--Error occurs here

      }
   }
}

[Steve_Lionel · Accepted solution]

You need to "export" the names of procedures you want to call in the DLL. In Intel Fortran, this is done with an ATTRIBUTES DLLEXPORT directive. I also see that the C# code describes the DLL routine as STDCALL. 

I think the following will do what you need: add the following line to the Fortran code after the FUNCTION statement:

!DEC$ ATTRIBUTES STDCALL, DLLEXPORT, ALIAS:"TSAT11" :: TSAT11

This has a side effect of making the argument P be pass-by-value. 

[jhlee0301]

Thank you for the solution.

I still have problem in C# WinForm project so I posted new question.

If you have solution for this please review my posting.

https://community.intel.com/t5/Intel-Fortran-Compiler/Call-Fortran-dll-in-C-Winform/m-p/1204526#M151516