Calling Visual Fortran DLL from Visual C#

[kim7]

Hello,

I am writing an application using Visual C# .NET. The application calls Visual Fortran 6.6A subroutines in a DLL.

I have been able to call test Fortran subroutines in the DLL from C#, change values in floating point and integer arrays in the subroutines and pass the new values back to C#.

I am having trouble passing string values to a Fortran subroutine. I can pass one string and access the string. I was able to use a System.Text.Stringbuilder and with some odd manipulation in C# of the returned values, I was able to change the string in a subroutine and pass the new string back to C#. But I cannot pass more than one string.

Please reply with any suggestions or hints you might have for this. Thank you.

Best,


Kim

[durisinm]

Fortran strings are passed with a hidden length. Visual Fortran's on-line help has a "mixed-language programming" topic under the "Strings" heading that explains a lot about this. There is no specific information about exchanging strings between C# and Fortran, but it will probably help you. The example programs that come with VF include ones dealing with passing strings.

Mike

[kim7]

Mike,

Thanks much for your reply. I have printed out the Visual Fortran help information on mixed languaged programming and strings and think this is key information. I do not have success to report yet and will work on this again on Monday when a colleague with much expertise in Fortran returns from vacation.

Best,

Kim

[durisinm]

The Canaima Software Web site has some good manuals and tutorials about calling Visual Fortran from Visual Basic. I think that they contain a discussion of passing strings that may help you.

Mike

[kim7]

Mike,

Thanks for the additional site. I am keeping it for future reference.

I found an example from the Compaq Fortran web site to be helpful.

This morning we successfully passed from Visual C# to Visual Fortran a string by value (not to be changed) and another string by reference (changed on the Fortran side and successfully read back on the C# side).

C# programmers, also look at the "Platform Invoke Tutorial" in Help for Visual Studio.

Best,

Kim


Visual C#

using System.Runtime.InteropServices;

...

[DllImport("TestFOR.dll")]
public static extern void HELLO_S(
[MarshalAs(UnmanagedType.LPStr)]
System.Text.StringBuilder TEST,
[MarshalAs(UnmanagedType.I4)]
int TEST_LEN,
[MarshalAs(UnmanagedType.LPStr)]
System.Text.StringBuilder MESSAGE,
[MarshalAs(UnmanagedType.I4)]
int MESSAGE_LEN);

...

StringBuilder TEST = new StringBuilder("TESTVAL");
StringBuilder MESSAGE = new StringBuilder("01234567890123456789012345678901234567890123456789012345678901234567890123456789"); // 80 chars. max

...

HELLO_S(TEST, TEST.Length, MESSAGE, MESSAGE.Length);


Visual Fortran

SUBROUTINE HELLO_S(TEST,MESSAGE)

! Expose subroutine HELLO_S to users of this DLL
!
!DEC$ ATTRIBUTES DLLEXPORT::HELLO_S

CHARACTER TEST*(*)
CHARACTER MESSAGE*(*)
WRITE(10,'(1X,A)') 'TEST="'//TEST//'"'
IF(TEST.EQ.'TESTVAL') THEN
WRITE(10,'(1X,A)') 'TEST.EQ.TESTVAL'
ELSE
WRITE(10,'(1X,A)') 'TEST.NE.TESTVAL'
ENDIF
L=LEN(TEST)
WRITE(10,*) 'LEN(TEST)=',L
L2=LEN(MESSAGE)
WRITE(10,*) 'LEN(MESSAGE)=',L2
WRITE(10,'(1X,A)') 'MESSAGE="'//MESSAGE//'"'
MESSAGE='Test Message'//CHAR(0)
WRITE(10,'(1X,A)') 'MESSAGE="'//MESSAGE//'"'
RETURN
END

[durisinm]

Steve,

Is this a good candidate to include with VF examples? More and more people are going to be mixing VF with .NET languages.

Mike

[Steven_L_Intel1]

I'm sure we'll be adding examples like this in the future.

Steve