Matlab function in VB.NET does not work. What's wrong with it?

[Reprod]

there's nothing wrong with the com object... at least there wouldn't be if you actually instanciated it... you declared calcul as a tesxting_COM.Class1 ... that's fine... but you never created the instance...

Imports testing_COM

Public Class Form1

Dim calcul As testing_COM.Class1

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  calcul = new testing_COM.Class1 ' <-- THIS is what you forgot to do
  Dim result As Object = New Object()
  calcul.test(1, result, 16) '<-- had you checked here, you would have seen that "calcul" was nothing and thus the source of the error.

End Sub

End Class

-tg

Also error: "COMException was unhandled: Undefined function or method 'sqrt' for input arguments of type 'int32'.
Error in => test.m at line 2"

Function in Matlab (test.m):

function t = test(n)
t=sqrt(n);
end