Transferring arrays from C DLL's to VB.Net

[Michael Fitzpatrick]

Transferring arrays from C DLL's to VB.Net

I have a DLL written in C. This DLL reads a text file and creates a several
very large arrays, 500,000 points and even larger. I would like the get the
data in VB.Net so that I can plot it. Presently I am creating an equally
sized array in VB and copying the data from the DLL's array into the VB
array.

There must be a better way. I looked into using a SAFEARRAY but it looks to
me that VB.Net doesn't use them as a native array structure.

Can I get the DLL's pointer to the array and use it in VB.Net?
Can I otherwise package the array in the DLL so that I do not need to
duplicate it?

################################
Details:

The VB.Net program is just a UI for the DLL's and allows the user to select
the file to process and will get the data and plot it, so the VB is just a
shell for the real work being done in the C DLL's.

The DLL's are used in a test system. The data is read from a text file and
processed, so the arrays are not the data in the text file, but rather an
analysis of that data. C Dll's are used so that I can be platform
independent, that is, I need to be able to use this DLL code in other test
systems like National Instruments Labview and Agilent Vee.

I have the system working now, except that it is slower and uses more
resources because of the arrays, there are 30 in all. I usually duplicate 2
at a time, but now I find myself re-reading the same arrays several times
and I am looking for a way to improve performance.

 

[Scott Wisniewski]

You can create a managed C++ class that implements an appropriate collection
interface,
wrapping up a pointer to the array.

If you do not require random access to the array elements you can get away
with
implementing either System::Collections::IEnumerable or
System::Collections::ICollection.
If you require random access to the array you would need to implement
System::Collections::IList, or add an indexer to your class.

 

[Guest]

You could use safearrays and then embed marshalling commands in th
dllimport function or declare function prototypes that you are using in VB.NE
to call the c routines. Don't forget to specify the subarraytype when marshalling.