C# & MATLAB interoperability for non-matrix datatypes

Question

I'm writing a C# program that needs to call MATLAB processing routines. I've been looking at MATLAB's COM interface. Unfortunately, the COM interface appears to be rather limited in terms of the types of data that can be exchanged. Matrices and character arrays are supported, but there doesn't seem to be support for exchanging struct data or cell arrays between C# and MATLAB using the COM interface. For example, in the following code (assuming that a DICOM image named IM000000 is present in the appropriate file folder), the MATLAB variables 'img' and 'header' are a 256x256 int16 matrix and a struct, respectively. The GetWorkspaceData call works fine for 'img', but returns null for 'header' because 'header' is a struct.

public class MatlabDataBridge
{
   MLApp.MLAppClass matlab;

   public MatlabDataBridge()
   {
      matlab = new MLApp.MLAppClass();
   }

   public void ExchangeData()
   {
      matlab.Execute(@"cd 'F:\Research Data\'");
      matlab.Execute(@"img = dicomread('IM000000');");
      matlab.Execute(@"header = dicominfo('IM000000');");

      matlab.GetWorkspaceData(@"img", "base", out theImg);   // correctly returns a 2D array
      matlab.GetWorkspaceData(@"header", "base", out theHeader);   // fails, theHeader is still null

   }  
}

Is there a suitable workaround for marshalling struct data to/from MATLAB using the COM interface? If not, is this functionality well supported by the MATLAB Builder NE add-on?

Answer 1

I ended up using the MATLAB Builder NE add-on to solve the problem. The code ends up looking something like this:

using MathWorks.MATLAB.NET.Arrays;
using MathWorks.MATLAB.NET.Utility;
using MyCompiledMatlabPackage;   // wrapper class named MyMatlabWrapper is here

...


matlab = new MyMatlabWrapper();

MWStructArray foo = new MWStructArray(1, 1, new string[] { "field1", "field2" });
foo["field1", 1] = "some data";
foo["field2", 1] = 5.7389;

MWCellArray bar = new MWCellArray(1, 3);
bar[1, 1] = foo;
bar[1, 2] = "The quick brown fox jumped over the lazy dog.";
bar[1, 3] = 7.9;

MWArray result[];
result = matlab.MyFunction(foo, bar);

// Test the result to figure out what kind of data it is and then cast
// it to the appropriate MWArray subclass to extract and use the data

Answer 2

Consider having a look to LabSharp (a wrapper around the Matlab engine API). You can then exchange structure like this:

var engine = Engine.Open(false);    
var array = MxArray.CreateStruct();

array.SetField("MyField1", "toto");
array.SetField("MyField2", 12.67);
engine.SetVariable("val", array);

NB: This LGPL wrapper is not mine, please have a look to its API for more details.