Fortran Dll in C# passing strings problem

[EDN Admin]

Hi I have to link C# with a fortran Dll. I have a fortran definition of a subrutine:

<div style="color:Black;background-color:White; <pre>
subroutine SETUP (nc,hfiles,hfmix,hrf,ierr,herr)

c
c define models <span style="color:Blue; and initialize arrays
c
c A call <span style="color:Blue; to this routine is required.
c
c inputs:
c nc--number of components (1 <span style="color:Blue; for pure fluid) [integer]
c hfiles--array of file names specifying fluid/mixture components
c [character*255 variable] <span style="color:Blue; for each of the nc components;
c e.g., :fluids:r134a.fld (Mac) <span style="color:Blue; or fluidsr134a.fld (DOS) <span style="color:Blue; or
c [full_path]/fluids/r134a.fld (UNIX)
c hfmix--mixture coefficients [character*255]
c file name containing coefficients <span style="color:Blue; for mixture model,
c <span style="color:Blue; if applicable
c e.g., fluidshmx.bnc
c hrf--reference state <span style="color:Blue; for thermodynamic calculations [character*3]
c <span style="color:#A31515; DEF: <span style="color:Blue; default reference state <span style="color:Blue; as specified <span style="color:Blue; in fluid file
c is applied <span style="color:Blue; to each pure component
c <span style="color:#A31515; NBP: h,s = 0 at pure component normal boiling point(s)
c <span style="color:#A31515; ASH: h,s = 0 <span style="color:Blue; for sat liquid at -40 C (ASHRAE convention)
c <span style="color:#A31515; IIR: h = 200, s = 1.0 <span style="color:Blue; for sat liq at 0 C (IIR convention)
c other choices are possible, but these require a separate
c call <span style="color:Blue; to SETREF
c outputs:
c ierr--error flag: 0 = successful
c 101 = error <span style="color:Blue; in opening file
c 102 = error <span style="color:Blue; in file <span style="color:Blue; or premature <span style="color:Blue; end of file
c -103 = unknown model encountered <span style="color:Blue; in file
c 104 = error <span style="color:Blue; in setup of model
c 105 = specified model <span style="color:Blue; not found
c 111 = error <span style="color:Blue; in opening mixture file
c 112 = mixture file of wrong <span style="color:Blue; type
c 114 = nc<>nc from setmod
c herr--error string (character*255 variable <span style="color:Blue; if ierr<>0)
c [fluid parameters, etc. returned via various common blocks]

character*3 hrf
character*255 hfiles(ncmax),hfmix
[/code]

<br/>
and I have made in C# the following prototype:


<div style="color:Black;background-color:White; <pre>
<span style=<span style="color:#A31515; "white-spacere"> [DllImport(<span style="color:#A31515; @"Crogram FilesREFPROPrefprop.dll",
<span style="color:Green; //CallingConvention=CallingConvention.StdCall,
<span style="color:Green; //CharSet = CharSet.Ansi,
EntryPoint = <span style="color:#A31515; "SETUPdll")
]
<span style="color:Blue; public <span style="color:Blue; static <span style="color:Blue; extern <span style="color:Blue; void Setup(<span style="color:Blue; ref <span style="color:Blue; long nc,
<span style="color:Blue; string hfiles,<span style="color:Blue; long hfiles_len,
<span style="color:Blue; string hfmix,<span style="color:Blue; long hfmx_len,
<span style="color:Blue; string hrf,<span style="color:Blue; long hrf_len,
<span style="color:Blue; ref <span style="color:Blue; long ierr, <span style="color:Blue; ref <span style="color:Blue; string herr,<span style="color:Blue; ref <span style="color:Blue; int herr_len);
[/code]

<br/>
The problem is that when I access the function I receive the following error:


Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

What it is wrong with my code? Can anyone help me?

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