Fortran dll call from VB.Net - vb.net

Question

Below code contains the fortran77 dll call from vb.net with two-dimensional array and struture. Input Parameters are flg & a_in(,), it calculates some value and in turn it populates the output array in a_pn(,) and a_vOUT(,). There is a addressof callback function used in fortran dll. I wasn't able to fetch the output values to proceed further.
---VB.Net Code with Fortran dll call---
Dim flg As Int32
Dim a_in(,) As Double --- Input array with values
Dim a_PN(,) as Double ----Output array return from Fortran77 DLL (Value calculated from a_in(,) array and returns)
Dim a_vOUT(,) as Double ----Output array return from Fortran77 DLL
Dim a_Flgs(,) as Int32
Dim a_b() as byte
Dim a_string1 As New VB6.FixedLengthString(255)
Public Structure Case_Info
Dim nx() As Double
Dim ny() As Double
Dim tc() As Double
Dim ip(,) As Double
End Structure
W_Ftrn(Flg, a_in(1, 1), a_PN(1, 1),a_vOUT(1, 1), a_Flgs(1, 1), .TC(1), .ip(1, 1),.nx(1), .ny(1), AddressOf CallBack0, AddressOf CallBack1, a_b(1), a_string1.Value, 255)
---Fortran declaration in vb.net--
Public Declare Sub W_Ftrn _
Lib "D:\Proj2\Fortran.DLL" Alias "W_Ftrn" _
(ByRef flg As integer,ByRef a_in As Double, ByRef a_PN As Double, ByRef a_vOUT As Double, ByRef a_Flgs As Int32, _
ByRef constray As Double, ByRef ipn As Double, _
ByRef aGX%, ByRef aGY#, _
ByVal cbaddr0 As long,ByVal cbaddr1 As long,ByRef bPlain As Byte, _
ByVal s1 As String, ByRef L1 As Int32)

Answer 1

My guess is that you are going to have to do your own manual copy-in and copy-out of the array-cells that you want to write to before and after the F77 call. Something like this:
Dim a_in1 As Double
Dim a_PN1 as Double
Dim a_vOUT1 as Double
Dim a_Flgs1 as Int32
Dim a_b1 as byte
Dim nx As Double
Dim ny As Double
Dim tc As Double
Dim ip1 As Double
' copy-in, manually '
a_in1 = a_in(1, 1)
a_PN1 = a_PN(1, 1)
a_vOUT1 = a_vOUT(1, 1)
a_Flgs1 = a_Flgs(1, 1)
tc = .TC(1)
ip1 = .ip(1, 1)
nx = .nx(1)
ny = .ny(1)
a_b1 = a_b(1)
W_Ftrn(Flg, a_in1, a_PN1,a_vOUT1, a_Flgs1, TC, ip1, nx, ny, AddressOf CallBack0, AddressOf CallBack1, a_b1, a_string1.Value, 255)
' copy-out, manually '
a_in(1, 1) = a_in1
a_PN(1, 1) = a_PN1
a_vOUT(1, 1) = a_vOUT1
a_Flgs(1, 1) = a_Flgs1
.TC(1) = tc
.ip(1, 1) = ip1
.nx(1) = nx
.ny(1) = ny
a_b(1) = a_b1