Dll imported functions not working on C# but do on vb6

Question

I'm using an old dll file function that is currently working ok in vb6, declared like this:

Public Declare Function DecOutb Lib "DecLib.dll" Alias "_outportb@8" _
(ByVal PortAddress As Long, ByVal state As Byte) As Long

Public Declare Function DecOutLong Lib "DecLib.dll" Alias "_outport@8" _
(ByVal PortAddress As Long, ByVal state As Long) As Long

The implementation of the funcion is this:

k = DecOutLong(ad_addr, Data)

It returns k=1 when it is successful, and it is.

However when I put this on my .net C#, even if I don't get any warning or error, but the function does not work, returning k=0. The declaration I'm making is like this:

[DllImport("DecLib.dll", EntryPoint = "_outport@8", CallingConvention = CallingConvention.StdCall)]
public static extern int DecOutLong(int PortAddress, int State);

And the implementation is this:

k = DecOutLong(ad_addr, DATA);

Answer 1

FIXED, I followed tcarvin's advice and set it to compile to x86 instead of "Any PC". I'm suspecting there is more to clarify in this situation, but at least it works.