How can I call a dll from VB.NET for a particle simulation?

[Pauly Man]

I've created a dll in c++ that runs a 4th order Runge-Kutta on user supplied data. I want to use it in a particle simulation, which I already have in vb.net. The trouble is I have no idea how to call the dll from within vb, any ideas?

ps- I've tried using the info provided on msdn, but I'm not sure if I'm doing it right. Basically the dll file is called "RungeKuttaDLL.dll", the lib file is called "RungeKuttaDLL.lib" and the function for export within the dll is called "RungeKutta". msdn gave me this info:

Private Declare Function RungeKutta Lib "c:\Documents and Settings\PB Customer\My Documents\Visual Studio Projects\VB\NumericalMethods\RungeDLL\RungeKuttaDLL.dll"(ByVal X0 As Double, ByVal Y0 As Double, ByVal H As Double, ByVal N As Integer) As Double

It doesn't work though.

 

[Greg Bernhardt]

Put your DLL in your bin folder. Then in your code at the top type "Imports ..." (... = whatever namespace is in your dll). Now you have access to your classes in the dll.

 

[Pauly Man]

I still can't get it to work. I looked at some examples on the net, and they all seem to work, but only have one function in the dll, or are API calls. I get an error message when I try and compile, and it tells me it can't find an entry point called RungeKutta. I've looked all over the ent, and there is nothing of use that I can find. I may just give up and work out how to program it all in c++, vb seems way too complicated and too much trouble, which is an oxymoron when you think about it.

 

[Greg Bernhardt]

Your namespace and or classes must not be setup right then. Copy your code in here.

btw, why are you using VB and not C#? C# is a lot closer to C++ and Java.

 

[Pauly Man]

Module RungeDLL

Declare Function RungeKutta Lib "c:\Documents and Settings\PB Customer\My Documents\Visual Studio Projects\VB\NumericalMethods\RungeDLL\bin\RungeKuttaDLL.dll" Alias "RungeKutta" (ByVal X0 As Double, ByVal Y0 As Double, ByVal H As Double, ByVal N As Integer) As Double

End Module




Imports RungeDLL

Public Class Form1
Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

Public Sub New()
MyBase.New()

'This call is required by the Windows Form Designer.
InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub

'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
'
'Form1
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(292, 266)
Me.Name = "Form1"
Me.Text = "Form1"

End Sub

#End Region

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
RungeKutta(0.0, 0.0, 0.2, 5)
End Sub
End Class



I have never really thought about using c# before, maybe I should.

 

[Greg Bernhardt]

oh it's a regular C++ DLL, you know there is also a C++.net

anyway here you go
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfSystemRuntimeInteropServicesDllImportAttributeClassTopic.asp

 

[Pauly Man]

I'm using c++.net, well vs.net anyway.

 

[Pauly Man]

I've worked it out. I don't fully understand why it works now, but it does, so Hooray!